Reuse of excavated peat on wind farm development sites

Research completed: January 2025

DOI: http://dx.doi.org/10.7488/era/6333

Executive summary

Minimising peat excavation is crucial in order to avoid carbon emissions, protect biodiversity and ensure downstream water quality. Built development on peatlands results in the excavation and disturbance of peat. In order to ensure evidence-based planning and consenting decisions there is a need to gather evidence on the impacts and opportunities regarding the reuse of excavated peat. This will help to inform how best to balance the benefits of renewable energy with the need to protect and restore peatland habitats, ensuring sustainable development practices.

This project investigates the opportunities, impacts, and challenges associated with the reuse of excavated peat from windfarm construction sites. It provides a greater understanding of the current knowledge concerning wind farm development on peatland, peat and peaty soils across Scotland. We propose a hierarchy of peat reuse options based on environmental impact and offer recommendations for data collection and monitoring to enhance the evidence base.

The research combined a review of published evidence with stakeholder engagement and site visits.

Findings

We found very little academic research specifically investigating best practice for the reuse of peat on windfarms. We therefore used stakeholder discussions and site visits to understand the current situation, what is occurring at different sites within Scotland, and likely environmental costs and benefits of different reuse options.

Key issues

Avoidance of peat excavation: Minimising peat excavation is crucial. As a critical first step of the mitigation hierarchy, different stakeholders agree the need to limit volumes to protect peatland, biodiversity, and maintain hydrological connectivity.

Preparation and planning issues: Site surveys often lack the requisite detail to effectively avoid deep peat areas during construction. It also leads to problems with planning how to reuse greater volumes of peat than expected. Additional training for construction operatives would enable them to minimise peat disturbance and maintain the excavated peat’s structure.

Carbon storage: Accurate carbon calculations are needed to fully understand the impact of the wind farm. However, this study found that more peat is often excavated than planned, highlighting the need for greater accuracy in carbon excavation measurements. Monitoring the condition of reused peat is also necessary to enable better understanding of carbon storage and other ecosystem services.

There are a range of construction activities that result in the excavation of peat, such as the construction and maintenance of roads and tracks, compounds and substations, crane pads and turbine blade laydown areas, cabling, drainage ditches and borrow pits. The main reuse methods include borrowpit reinstatement, restoration activities and landscaping. These reuse options may have varying environmental outcomes (Table 1), consideration for which needs to be part of the planning process when constructing a wind farm and planning the reuse of excavated peat within the project.

Recommendations

Recommendation 1: Guidance on excavation peat reuse

Because detailed evidence to confirm the different environmental outcomes is not available, we recommend a simple hierarchy of peat reuse options accompanied by additional guidance and requirements, which are essential for maximising environmental outcomes. We recommend this comprises:

• Recommendation 1a: Preparation and planning steps:
  • Avoid / minimise peat excavation wherever possible and
  • Appraise site circumstances and locally relevant potential reuse options
• Recommendation 1b: Hierarchy of peat reuse
• Recommendation 1c: Peat reuse implementation principles: to guide the site-specific choice of methods and implementation to maximise environmental outcomes.

The hierarchy is not useable as a standalone guide – it must be accompanied by the additional components – as shown in Figure 1 below.

Figure 1 Guidance for Excavated Peat Reuse

 

Recommendation 2: Environmental outcomes framework

To ensure the multiple potential environmental benefits of peat reuse are considered, avoiding a single-issue focus.

To ensure a balanced approach to peat reuse, we recommend targeting the following environmental outcomes:

• Minimising carbon loss: Reducing carbon emissions from excavated peat.
• Positive biodiversity outcomes: Achieving biodiversity goals at both local and national levels.
• Ensuring downstream water quality: Minimising sediment and nutrient load in water bodies.

Recommendation 3: Enhanced monitoring of environmental outcomes from reuse of peat

Enhanced research and monitoring are required to improve and inform the reuse hierarchy and implementation of best practice techniques going forward:

• Post-construction assessment: Providing accurate peat excavation volumes at the end of construction to build a dataset to be used within the sector for more accurate carbon calculations and reuse planning.
• Post-construction monitoring: Regular monitoring of wetness of the peat, carbon fluxes and vegetation surveys to understand the broader environmental impact of peat reuse.
• Data sharing and collaboration: Encouraging greater data sharing and collaboration between energy companies and the academic community to refine the reuse hierarchy and best practice in the field.

Next steps and future research

These results highlight our current understanding of peat reuse methods occurring in wind farm construction in Scotland. We have highlighted which environmental issues are critical and how the reuse of peat can maintain the habitat, allowing for environmentally conscious construction techniques to take precedence.

However, a clear conclusion from the information gained during this process is that planning prior to construction is key, as well as ensuring that stakeholders work together to achieve best practice.

After these main outcomes from the hierarchy, the attention needs to focus on delivering site specific reuse. It also became apparent that although there is a lot of knowledge within the peatland and wind farm sectors, there have been limited studies collecting data to inform best practice. This needs to be encouraged to understand current research gaps and advise on the right management methods to reduce peatland degradation in the long term.

Table 1: Synthesis of reuse options and simplified overview of potential environmental outcomes (Note: this table summarises potential outcomes indicated by research during this study, but evidence is limited and site-by-site circumstances vary significantly so currently this differentiation on environmental grounds cannot be fully reflected in the recommended ‘hierarchy of peat reuse’.)

Method of reuse	Carbon store	Hydrology connectivity	Availability	Comment
Borrow pit reinstatement	++ Low risk of carbon loss Low chance of carbon sequestration (carbon increase) in the long term	+ Only if well planned, with impermeable layers and outflows built in	+++ Large storage potential, should have capacity for all excavated peat, however where there is more (or less) peat than planned may lead to issues	Borrow pits have potential to provide an environmentally robust reuse option, however only if best practice is followed and there are contingencies in place if changes in planned volumes occur
Around turbine foundations and crane pad verges	— High risk of carbon loss through peat drying out and erosion	– When constructed these areas will automatically have drainage channels cut. The reuse of peat here will likely be impacted by this drainage	+ Small volume	Use to encourage vegetation re-growth around construction areas. Often used as a way of merging the built infrastructure with the surrounding landscape
Side of road/ track or “landscaping”	– Risk of carbon loss through peat drying out and erosion, however if vegetation regrowth occurs this is less likely	– Addition of peat should connect the reused peat with wider environment to maintain hydrology, however this depends on flow patterns and drainage channels across roads	+ Small volume	If vegetation regrowth occurs and there is limited bare peat this has potential to become part of the wider landscape
Incorporation of peat in restoration / reinstatement projects	+++ Low risk of carbon loss, has potential to build carbon (dependent on restoration / reuse project)	+++ If well planned, should have hydrological connectivity with landscape	+ Small volume	Usually these projects are highly monitored to assess progress – useful for data gathering in the short term alongside the benefits of using excavated peat in areas that may have been degraded previously

 

 

Glossary

Acrotelm	The upper of two layers in peatland system. Acrotelmic peat consist of fresh or newly decomposed peat forming vegetation and is generally quite fibrous This layer possesses some tensile strength and depending on the height of the water table can be anoxic.
Arisings	Excavated material that is created during excavation and construction activities.
Blanket Bog	A type of peatland that is relatively rare globally, however, commonly found in Scotland, due to its cool, wet climate. Blanket bogs are characterised by a peat depth of 0.5 to 3m, situated on flat or gentle slopes and have poor drainage (see ‘Raised Bog’ below as alternative type).
Borrow pit	In windfarm development, an excavation site (or quarry) where materials like soil, gravel, or rock are dug up for use in the construction. These materials are typically used for building access roads, turbine foundations, and other infrastructure.
Catotelm	The lower of two layers in a peatland system. Catotelmic peat consist of waterlogged, highly decomposed dense organic material with low tensile strength. This layer is highly amorphous and tends to disrupt completely on excavation causing difficulty with handling and storage.
Dissolved organic carbon	Organic carbon compounds that can pass through a filter with a maximum pore size of 0.7 micrometres.
EU Habitats Directive (92/43/EEC)	A European directive for the protection and conservation of natural habitats and of wild fauna and flora which has been transposed into Scottish legislation through the Habitats regulations, amended in 2021 post EU exit. https://eur-lex.europa.eu/eli/dir/1992/43/oj/eng
Peat	Peat is an organic material that forms in cool, waterlogged conditions. It consists of partially decomposed organic matter, primarily plant material and no mineral fraction. Over time, the accumulation of this organic material creates a peat and peaty soil that are rich in carbon.
Peat soil	Also referred as organic soil, in Scotland it is defined as soil with a surface peat layer with more than 60% organic matter and of at least 50cm thickness.
Peaty soil	Organo-mineral soil which have a shallow peat layer at the surface (less than 50cm thickness) over mineral layers.
Peatland	Peatland is defined by the presence of peat soil or peaty soil types. This means that “peat-forming” vegetation is growing and actively forming peat, or it has been grown and formed peat at some point in the past. It is a type of wetland ecosystem where peat material accumulates. These areas are characterized by waterlogged conditions that slow down the decomposition of organic matter, leading to the formation of peat. Peatlands have a specific type of vegetation, are rich in biodiversity and play a crucial role in carbon storage. Peatlands can include blanket bog, upland raised bog, lowland raised bog and fens.
Peatland Management Plan	A Peatland Management Plan used in development projects on peat typically includes several key components to ensure the sustainable use and conservation of peatland ecosystems. The plan describes baseline peat conditions, detail on excavation and reuse volumes and potential impact, how the peat will be handled, stored, or reused once extracted. This is an integral part of consent conditions.
Piled foundations	Deep foundations that use long, thin columns (piles) driven or drilled into the ground to support wind turbine structures. These foundations are essential for ensuring stability, especially in areas with weak or variable soil conditions and high-water tables. Also reduce the volume of peat needed to be excavated.
Priority peatland habitat	Peatland habitats can be divided into four broad classes (blanket bog, upland raised bog, lowland raised bog and fen), depending on the types of plants that formed the peat. Priority peatland habitats are sub-sets of these broad habitats which have been recognised under the Scottish Biodiversity Framework as being important to protect for their conservation and biodiversity value.
Raised Bog	A type of wetland characterized by a dome-shaped surface of peat, formed by the accumulation of partially decayed plant matter, which rises above the surrounding groundwater levels and is primarily fed by rainfall rather than groundwater.
Reinstatement	Using peat and/or peatland vegetation that has been removed or excavated during the construction of a development, often surrounding infrastructure. This form of peat use involves protecting excavated peat, and returning it to where it was taken from, in its original order (acrotelm overlying catotelm). This should aim to reinstate the hydrology of the returned material to support peatland function following best practice, although full return of function is very difficult to achieve.
Restoration	Carrying out interventions which in combination with natural processes restores the hydrological function, coverage and condition of peatland habitat vegetation, resulting in a peatland that is actively forming peat and hence sequestering carbon. Further detail will be stated in the forthcoming Scotland’s Peatland Standard.
Revegetation	Using excavated peat and/or vegetation in the surrounding construction infrastructure or for landscaping. This form of peat use will often result in revegetation but may not result in functioning peatland. Nevertheless, it can have a role in protecting the surrounding peatland conserving carbon and biodiversity providing that best practice is followed.

Abbreviations

CO2	Carbon dioxide
DOC	Dissolved organic carbon
ECoW	Ecological Clerk of Works
GHG	Greenhouse Gas
IUCN	The International Union for Conservation of Nature
ha	Hectares
HRA	Habitats Regulations Appraisal
km	Kilometres
kWh	Kilowatt-hour
m	meters
MW	Megawatt
NPF4	National Planning Framework
PEAG	The Scottish Government’s Peatland Expert Advisory Group
PMP	Peatland Management Plan
POC	Particulate organic carbon
REA	Rapid evidence assessment
SEPA	Scottish Environment Protection Agency
WMLR	Waste Management Licensing (Scotland) Regulations

Introduction

Aims and scope

This project explored opportunities, impacts and challenges for the reuse of excavated peat from windfarm development sites. It is intended to inform application of National Planning Framework 4 (NPF4), regarding the development of wind farms on peatland, peat and peaty soils. It aimed to provide recommendations for a hierarchy of peat reuse options based on environmental impact along with recommendations for data collection and monitoring to continually improve and update the evidence base.

The project focused on gathering evidence of impacts and opportunities for excavated peat reuse on-site but also considered potential for positive off-site opportunities. Evidence of environmental costs and benefits in terms of emissions, peatland function, habitat, biodiversity, hydrology, stability and structure in relation to reuse practices was evaluated.

Defining ‘reuse of peat’ for this report

This report was commissioned to understand the reuse of peat on wind farm sites during the construction process. We recognise there are differing definitions of “reuse”.

Throughout the study we adopted the definition of “reuse” of peat as:

the use of peat and/or peatland vegetation that has been excavated during the construction of a wind farm.

In this context, the “reuse” of peat can involve reinstatement, revegetation or restoration processes both onsite and offsite, during the construction of a wind farm.

Research methods

A combination of research methods were used:

• A Rapid Evidence Assessment to gather and evaluate the academic literature and other relevant studies.
• Desk-based evaluation of existing wind farm developments on peatland in Scotland to understand current practices.
• Site visits to active and completed wind farm developments on peatland to observe examples of reuse practices in situ.
• Stakeholder engagement, via discussions during site visits, individual research interviews and a workshop to complement desk-research.

It was anticipated that there was limited literature available – in the absence of this, the site visits and stakeholder engagement were critical to the project. Full details of methods are provided in the Appendices.

Background

Scotland is committed to reaching net zero by 2045, how we use and manage our land is vital to achieving this, including the use of land to produce renewable energy. Balancing the benefits from renewable energy with land-based emissions and nature and biodiversity goals is vital, particularly where wind farms intersect with sensitive habitats, like peatland and on carbon-rich soils.

Globally, peatlands are the largest terrestrial carbon store estimated to hold 660 gigatonnes of carbon and 10% of non-glacial freshwater, however, only 17% of these ecosystems are protected (Austin et al., 2025). Globally, 20% of all blanket bogs are located within the UK and Ireland[1]. In Scotland alone, blanket bogs cover around 1.8 million hectares, which is 23% of the land area (Ferretto et al., 2019). Situating new wind farms in the right location is crucial. Although wind farm developments are expected to save carbon emissions by offsetting fossil energy sources (Renou-Wilson and Farrell, 2009), where wind farms are situated on peatlands, there is a risk of land-based carbon emissions, negating the reduction associated with offsetting fossil energy sources. The quality of the peatland habitat is an important factor, as areas that are already degraded and emitting carbon, could be improved through restoration of the whole environment. When applications are made for wind farm construction there are often enhancement conditions attached to these new developments leading to restoration, but some restoration may have been necessary without the wind farm construction occurring. Peatland condition categories[2] range from pristine, near natural, modified, drained and actively eroding in relation to GHG emissions and restoration potential. Historically, Scotland’s peatlands have not been protected across the whole habitat, with afforestation being prioritised up until recently. Wind farm construction in these areas, is likely to lead to environmental improvements, with stakeholders working together to reduce peatland degradation and ambitious programmes of peatland restoration being undertaken.

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[1] https://www.wwt.org.uk/discover-wetlands/wetlands/peat-bogs

[2] https://www.nature.scot/sites/default/files/2023-02/Guidance-Peatland-Action-Peatland-Condition-Assessment-Guide-A1916874.pdf

Research findings

Availability of literature

Overall, the literature searches presented over fifty academic studies and governmental reports, which provided useful information related to the impact of landscape management on peatland as well as some interactions between peatland and wind farm developments. However, there were no empirical studies monitoring changes in reused peat on windfarm developments over time. This is a major research gap. Understanding how the reuse of peat may change the peat itself had to be extrapolated from studies measuring changes within laboratories or evaluations of the landscape scale after a number of years since wind farm construction had occurred. Studies did consider the impact of peat excavation on the environment, hydrology and risks of erosion or the degradation of the peatland habitat. The literature did present a large number of studies focusing on the restoration of peatland habitats, however, these were not readily extrapolatable to the current study on reuse of peat, as the parameters related to restoration are substantially different. A large number of the papers and reports were focused on the Scottish environment which suggests that Scotland is leading the way in this area of research.

Summary of stakeholder engagement achieved

We obtained contributions from 31 individuals during our stakeholder engagement (for a more in-depth synopsis of stakeholder engagement findings see Appendix). Stakeholders highlighted what they viewed as the positive features of some reuse options, such as where the water flows in borrow pits (one method of peat reuse) have been managed to keep the water table near the surface. Stakeholders we spoke to were aware of the gaps in evidence and lack of specific studies and so based their views on their own observations or monitoring on sites they were involved with. Overall stakeholders agreed that a number of factors need to be considered carefully to have any chance of achieving optimal environmental outcomes from reuse of peat on windfarm sites – simply putting peat in a convenient location on site would not be beneficial as peat would dry out, erode or lose its structure and functioning. Key considerations were – what was the condition of peat prior to excavation, the need to plan how to minimise disturbance, handling, drying and transport of peat after excavation, consideration of the water levels and flows, vegetation cover and the stability of reused peat in situ.

Summary of site research conducted

During five site visits across varied locations in Scotland, a range of different peat reuse practices were observed including:

• different approaches to infilling borrow pits,
• use in landscaping (for example alongside tracks or to cover cables),
• infill of other site features including historical peat cuttings,
• incorporation of peat into peatland restoration.

Across sites the condition of peat prior to excavation and reuse varied, as did the nature of reuse even where the same general type of reuse was used, for example borrow pit size, shape, fill level, structure, hydrology and vegetation varied across sites where this practice was used. For more information related to site visits see the Appendix.

Summary of literature and stakeholder research findings

In Scotland, peatlands store over 2,735 million tonnes of carbon covering approximately two million hectares (Smith et al., 2007), equating to around 25% of Scotland’s land area. These peatlands are often considered good candidates for onshore wind farms due to the windy and exposed environments they are located in and because they are often considered poor (or unprofitable) for other land uses, like forestry and farming activities.

The main construction activities which result in substantial disturbance for a wind farm development are track construction for maintenance and access roads, trenches for cabling, quarried aggregate extraction (borrow pits) and turbine foundation excavation. This large-scale disturbance can affect peat stability, degradation (such as habitat condition, plant assemblages, carbon storage, etc), as well as the hydrology of the habitat. Other disturbances are related to building infrastructure to support the wind farm development like crane pad constructions, temporary and permanent compounds, as well as substations to join the electricity generated to the grid. Estimates of the direct disturbance to the peatland habitat per wind turbine vary greatly but have been reported to be between 0.2 to 1 hectare per turbine, with the turbines within a wind farm usually taking up less than 10% of the wind farm area (Sander et al., 2024). However, if this area is on deep peatland, there will be greater environmental impact, than on shallow peat or mineral soils.

Larger turbines, which are more widely spaced (typically on a 300-500 m grid, with the distance between turbines around five times rotor diameter), capture energy on a much smaller spatial ‘footprint’ than smaller ones on wind farms (Renou-Wilson and Farrell, 2009). However, this is also site-dependent and varies if repowering occurs, as repowering may use the same footprint as the previous turbines, or it could locate the turbines at a new area within the development, thus increasing the environmental impact.

Construction of a wind farm requires a significant array of associated infrastructure to be installed, this infrastructure may have impacts on the surrounding peatland either through the removal of peat from that habitat, removal and replacement of peat in less suitable locations or reducing the quality of the environment within the area the peat was moved to, compression, flooding, drainage, erosion or mass movement of the peat (Lindsay, 2018). Active peatlands are hydrologically linked and naturally stabilised therefore if hydrologically disrupted, the stability can be lost (Wawrzyczek et al., 2018). An unstable habitat can lead to wider environmental problems, with issues greater than just carbon loss, for example peat slides.

Peat and windfarms in Scotland

Peat is an amorphous organic deposit, considered to be the largest terrestrial carbon store. Peat is highly compressible and porous consisting of up to 90% water by volume. Active peat-forming mire has also been found to be effective in delaying storm run-off, reducing soil erosion and retaining inorganic nutrients when it is undrained (Bragg, 2002).

Across Europe it has been calculated that 25% of peatlands are degraded (Tanneberger et al., 2021). Under the EU Habitats Directive (92/43/EEC), there are 36 European regions with designated blanket bogs and of these, 12 have wind farm developments, including 644 wind turbines, 253 km of vehicular access tracks and an affected area of ~208 hectares, mainly in Ireland and Scotland where the extent of peatland is also higher (Chico et al., 2023). However, when this is compared to the Scottish soil maps, the extent of wind farm developments in Scotland on peatland is even higher, with 1,063 wind turbines and 635 km of vehicular access tracks on peatland in Scotland alone according to national inventory data (Chico et al., 2023).

Currently, 48% of wind farms in Scotland have already been built on peat[1] with this number likely to increase in the future. Wind farm developments can have an impact on the peatland habitats and emissions, during construction, operation, and decommissioning stages. This reduces the wind farms’ ability to reach the goal of net zero. Using a carbon calculator[2] to assess the carbon saving of wind farm developments compared to carbon lost through construction on Scottish peatland provides guidance on a wind farm’s carbon footprint. However, due to the heterogeneity of peatlands and the lack of detail at the required scale when completing peatland surveys pre-planning, it has been found that the amount of peat excavated is often more than the amounts used within the carbon calculations.

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[1] John Muir Trust – Scotland’s peatland policy update.

[2] https://www.gov.scot/publications/carbon-calculator-for-wind-farms-on-scottish-peatlands-factsheet/

Current practices: excavation

Both in discussion with stakeholders and within the literature, the instability of peat deposits was highlighted, with small movements leading to slope terracing, slumps or the collapse of peat banks – these events are relatively common. Furthermore, disturbed peat can lose more than 50% of its strength compared to undisturbed peat and, in many cases, behaves as a viscous material that will readily flow, particularly when affected by high rainfall (Jennings and Kane, 2015). These inherent properties of peat carry risk and need to be considered during the wind farm construction process as the destabilisation of peat mass through drainage or excavation operations could lead to an increase in landslides / bog flow events (Dykes, 2022).

From discussions with stakeholders, it is clear that the exact volume of peat to be excavated can differ from estimates calculated in the EIA at application stage. This is usually due to a combination of initially unknown factors prior to the construction process – the exact depth, viscosity and bulk density of the peat material that needs to be excavated. Calculations are usually based on predefined excavation requirements for the size of the turbine alongside average peat depths for the area provided by preliminary site surveys, using an interpolated model of a peat depth probe survey. However, the depth of peat can also vary significantly over time, with changes in the peatland hydrology, leading to peat shrinkage occurring during drought conditions (Morton and Heinemeyer, 2019). Thus the timing of peat surveys may affect peat excavation calculations, as well as the scale of the survey and heterogeneity of the habitat. Table 2 describes common reasons for excavation as part of the construction process and how they differ in approach.

Table 2. Common reasons for excavation on site and how they differ in approach when applied to peat and peatland.

Excavation types	Approach
Construction and maintenance of roads and tracks	Significant lengths of tracks need to be created linking wind turbines and wind farm infrastructure. The main methods that can be implemented are either cut and fill or to introduce floating roads. These roads will impact the drainage of the surrounding peatland by blocking or modifying flow and if floating the peat below can also be compressed, exacerbating drainage issues.
Construction of crane pads	Crane Pads are usually located adjacent to the turbine foundations to facilitate turbine components being lifted during turbine erection and future maintenance or repairs. Depending on the load, crane pads are usually unpaved, however, compacted with layers of gravel. For some installations, the turbine foundation is used as a crane pad after initial construction.
Turbine blade laydown areas	A designated space near the turbine foundation where large components are stored before installation. These are often temporary excavations and reinstated after construction.
Cabling	Usually installed along tracks so typically does not require additional excavation, although may require a small amount of disturbance and/or influence the scheduling of any reinstatement following tracks.
Turbine base	The digging of the foundations of turbine bases generates large volumes of peat that need to be reused. They also introduce alkaline concrete into the environment which may impact the pH of the surrounding habitat and may require drainage installation to protect the foundation and avoid uplift.
Compounds and substations	Temporary compounds provide facilities for workers and equipment. Substations are usually permanent installations, often with steel frames and cladding, crucial for power collection and transmission. The peat needs to be removed, before a hardstanding area is laid, using gravel. These areas also need to be linked to the access roads early in the construction process.
Drainage ditches	Drainage is necessary around wind turbine foundations and wind farm infrastructure to maintain integrity and is usually a permanent feature of the windfarm. Often this leads to a lowering of water levels associated with drainage around infrastructure. Drainage may impact a much wider area than the drain margin and as well as lowering water levels surface subsidence may also occur.
Borrow pit	The volume of peat excavated depends on the depth at which usable aggregate materials are found. The quantity and quality of aggregate in the borrow pit can be hard to judge before the pit is opened so the volume of excavated peat may be higher or lower than anticipated.

Roads and tracks

Construction and maintenance roads and tracks are the most extensive direct impact of a wind farm on peatland as the roads need to allow access to every turbine, plus all the other infrastructure buildings but could also provide access to areas for restoration and enhancement activities. Initially, roads were just cuttings made on shallower peat down to the mineral base. However, this meant that the roads were lower than the surrounding peatland and frequently led to drainage issues.

Construction methods have adapted from just cuttings to the ‘cut and fill’ method (where the peat is dug out until the mineral subsoil is reached and backfilling the trench with aggregate until the road is around the same level as the surrounding bog surface (Lindsay, 2018)) or the preferred method of floating roads (using a geotextile mesh on top of deep peat). Floating roads have limited peat removal as a geotextile mesh is laid on top of the peat, with aggregate poured on top. Another geogrid may then be added with more aggregate before the final ‘running surface’ is laid (Lindsay, 2018).

Stakeholders described how the design of the road network through a wind farm is largely driven by the placement of the turbines (often on ridges which may be where the deepest peat is located) and following the contours of slope (increasing the distances of the road network within the peatland habitat). Tracks also need to bear large weights, for example, the cranes used for wind turbine construction can weigh up to 200 tonnes (this also has implications for the construction of crane pads). A study showed the orientation of the road in relation to the flow of water within a peatland had a large impact (Elmes et al., 2022) and led to flow obstruction and changes to the overall hydrology when running perpendicular to the flow in comparison to parallel. However, this sort of nuanced planning is rarely discussed as part of the construction process. Infrastructure like work compounds and substations also require access roads (with drainage). Thus, the size of the area of peat that is disturbed by the development may be greater than first considered.

Drainage

It was highlighted by stakeholders – and during the site visits – that drainage is usually the first construction activity occurring when developing wind farm infrastructure and is often necessary around the turbine bases and accompanying roads and tracks to reduce the risk of surface flooding. Drainage ditches are also excavated around wind farm foundations to improve the stabilisation of the turbine foundations and to protect machinery. This process of draining peatlands is known to be detrimental, causing subsidence through oxidation of the peat (Williams-Mounsey et al., 2021) and carbon loss. However, peat further away from the drainage ditch (> 1m) will only lose 20% of its previous moisture content, with the main effect of peatland drainage leading to removal of surface water rather than deep water-table drawdown (Lindsay, 2014). Drying of the peat may also lead to cracking, which may lead to rainwater penetrating the base of the peat and lubricate the interface between the peat and the mineral subbase (Lindsay, 2018).

Excavation works

Other large-scale disturbances of the peat are through excavation works. This can be for granular material used during construction (taken from borrow pits); excavation of the wind turbine foundations (although piled foundations can reduce the overall negative impact); and trenches for laying cabling/pipework, leading to substantial quantities of peat that may need to be stored prior to reuse. Piled foundations are usually built over deep peat, rather than excavating large quantities of peat; long, thin columns (piles) are driven or drilled into the ground to support wind turbine structures. These foundations reduce the volume of peat needed to be excavated whilst ensuring stability of the structure. Turbine towers experience large forces and must be placed on a solid foundation embedded within the underlying mineral subsoil or bedrock (Lindsay, 2018). Stakeholders said that often large quantities of peat may be deposited on nearby surfaces temporarily, if trucks aren’t continuously available to receive the excavated material, or dependent on the stage of the construction process. However, it is best practice to only move the peat once (to maintain structure and water content) thus, if the requisite planning is in place, a reuse strategy can be implemented where excavated material is moved to its final location in one step.

Stockpiling peat occurs where peat has been excavated and may need to be temporarily stored prior to reuse due to logistical constraints. As well as becoming a potential source of GHG emissions due to its exposure to aerobic conditions, when peat is stored, changes have been observed within its hydrochemistry, leading to it becoming less acidic and less nutrient-rich (Detrey, 2022). Over time, dewatering also occurs, which alters the hydrophysical properties (porosity) of the peat, these are key for sustaining critical peatland ecohydrological functionality (Lehan et al., 2022).

Ground preparation for stablishing crane pads and turbine blade laydown areas often requires excavating peat to create a stable foundation, leading to the removal of substantial peat volumes, with similar issues as discussed related to other excavation works. This will expand the area of impact further away from the turbine, with underlying changes to the hydrology, potential for release of GHG emissions, vegetation changes and degradation of peatland (Wawrzyczek et al., 2018). Some of these areas are temporary. For example, at some sites visited, areas which had previously been turbine blade laydown areas had peat reinstated and vegetation was able to naturally regenerate. However, this only occurs if it is part of the plan created by the developers, as some laydown areas will remain as areas with stable foundations which are available for future use.

Current practices: use of excavated peat – reuse practices

Excavated peat needs to be moved from the excavation site and is often initially stockpiled until an appropriate time for reuse. The time peat is stockpiled can vary substantially and will be impacted by where it was excavated from, the volume, and timing of the excavation related to overall construction of wind farm site. Lehan, et al., (2022) undertook a restoration study, to assess the impact of time on the hydrophysical properties of peat blocks that were stockpiled for 3, 7, 11, and 14 months. In this study, stockpiling peat was differentially impacted dependent on whether it was shallower or deeper peats, where limited impact from stockpiling was observed in the shallower peats, regardless of stockpiling time; however, in the deeper peats as stockpiling time increased there was a decrease in microporosity as well as mobile porosity (drainable porosity) (Lehan et al., 2022). It may be necessary to rewet the peat or aim to keep it wet whilst stockpiled.

Peat that has started to dry out will be less likely to function when reused. When the surface of the peat starts to dry out development of a hydrophobic layer may occur which causes irreversible changes to the ability of peat to be fully rewetted and reduces the infiltration capacity of the peat (Evans et al., 1999), increasing the desiccation of the peat overall and exacerbating the issue over time. There could also be a similar issue occurring around drainage channels, changing the overall hydrology of the habitat. There are a number of different potential reuse practices that occur on site, with varying quantities of peat, depth of peat and aims (Table 3).

Table 3. Generalised overview of current and potential future reuse practices for excavated peat

Reuse practice – onsite	Approach
Borrow pit reinstatement	Borrow pit reinstatement is one of the main sites for the reuse of peat. Guidance from SEPA highlights the WMLR[1] paragraph 9(1)b restriction that spreading on land subject to man-made development including quarry restoration should not exceed up to a maximum of 2 metres depth of material. [1] https://www.legislation.gov.uk/ssi/2011/228/contents
Around turbine foundations and crane pad verges	Use to reinstate the natural habitat and to encourage vegetation re-growth. Often used as a way of merging the built infrastructure with the surrounding landscape.
Side of road/ track or “landscaping”	This often occurs as a way of managing levels within the wind farm area, particularly where tracks have been constructed as floating and sometimes will become higher than the surrounding peatland. Vegetation at the side of the road and in the deposited material is not often considered and it is assumed natural regeneration will occur.
Incorporation of peat in restoration / reinstatement projects	This is not standard practice and has to date only occurred as part of research trials in areas directly adjacent to wind farm construction sites, where peat is used as a substrate for other restoration work. Often these sites are already partially disturbed due to the construction process or historically (through forestry, man-made drainage or cuttings). Examples from stakeholder discussions: used as a substrate to fill drainage ditches as part of wider restoration efforts within previously forested sites used as a substrate in the construction of dams to slow water down and hold within the landscape used to infill sites of historical peat cuttings (between turbines) hag infill in small areas within a degraded peat landscape Incorporating a layer of excavated peat in formerly forested sites undergoing restoration
Offsite use	Literature review referred to some potential ways to reuse peat off-site, but we found no evidence these are practiced in Scotland. All stakeholders stated that offsite reuse of peat does not occur. Suggestions have been made that peat could be used offsite, but these are largely hypothetical.

When excavating peat, it is imperative that the different layers are kept separate (acrotelm, catotelm) and not mixed with the underlying mineral substrate. This is because of the different properties of these layers and mixing will degrade the peat and reduce its function. Although peat excavation during wind farm construction is likely to occur, large excavations of peat should be avoided. Peatland management plans are mandatory when submitting planning applications for wind farm developments on peaty soils (as part of Policy 5 of the NPF4 framework). These plans provide a draft outline of the volume of peat to be excavated and the reuse activities that will be performed as part of the development. The reuse of peat is unlikely to have wider environmental benefits in areas that are not already disturbed by the wind farm construction or considered degraded; depositing excavated peat on undisturbed vegetation is likely to be detrimental.

To prevent the loss of carbon and the increase in GHG emissions which would occur from the degrading peat, it is essential that a considerable time is spent planning prior to the excavation process – reducing the distance the peat is moved, keeping the times the peat is moved to a minimum and understanding the volumes of peat involved. From discussions with a number of stakeholders it was suggested that, although the level of planning and motivations of the energy companies to reuse peat without degrading it is high, it is often dependent on the capabilities and understanding of the operators doing the work. A number of training courses have been organised for the construction sector specifically to improve this. However, these courses are voluntary. Training the construction sector in the importance of peatlands, restoration techniques and sensitivity during construction, will enable greater preservation of this valuable resource. In almost all discussions with stakeholders the reuse of peat occurred onsite, there were discussions regarding offsite use, but these were more abstract in terms of what was possible, rather than what was occurring. The reasoning given that the majority of reuse is on site is because the SEPA guidance[1] states that unless the excavated peat is used for construction purposes in its natural state on the site from where it is excavated, it will be subject to regulatory control and considered waste.

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[1] https://www.sepa.org.uk/media/287064/wst-g-052-developments-on-peat-and-off-site-uses-of-waste-peat.pdf

Overall, although the terminology is the same between different wind farm construction sites – the reuse of peat within borrowpits, landscaping or restoration, it is always site specific. There may be commonalities between the sites, for example, the need to maintain hydrological connectivity, and the importance of peatland vegetation. There will also be significant differences related to volume of peat excavated, previous habitat conditions and use, weather conditions and water table level, knowledge and preparedness of the contractors. Within 3.5.2, 3.5.3 and 3.5.4 we present case studies representing recent site visits.

Quantities of peat excavated during wind farm construction

Reviewing a number of reports, for example the “Good Practice during Wind Farm Construction” (NatureScot), “Research and guidance on restoration and decommissioning of onshore wind farms” (NatureScot), “Developments on peatland: guidance on the assessment of peat volumes, reuse of excavated peat and the minimisation of waste” (SEPA[1]), “Developments on Peat and Off-site uses of waste peat” (SEPA), as well as habitat management plans for specific wind farms, all state the importance of collecting relevant and detailed site investigation data at an early stage of the application process to enable a full understanding of the site character and to inform a more accurate design process. This is in full agreement with the academic literature (e.g. Jorat et al., 2024) and discussions with stakeholders. During the planning process the amount of peat that needs to be excavated and how it will be reused is identified (see Table 3 for an example of the average areas involved in excavations). However, due to the heterogeneity of the environment and the lack of granularity of peat depth survey’s there is some ambiguity related to total peat volumes until excavation has started.

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[1] Scottish Renewables, Scottish Environment Protection Agency. 2012. Guidance on the Assessment of Peat Volumes, Reuse of Excavated Peat and the Minimisation of Waste

 

Table 4. Area of turbines adapted from Albanito et al., 2022, also includes calculation of the average volume of peat per turbine taken from reviewed peatland management plans of operational wind farms in Scotland

	Wind farm capacity (megawatts, MW)
Input	<10 MW	>10 to <50 MW	>50 MW
Average length of turbine foundations (m)	10	15	22.18
Average width of turbine foundations (m)	10	15	22.18
Average surface area of turbine foundation (m2)	100	225	492
Average depth of excavated peat (m)	1.455	1.365	1.350
Average volume of turbine foundations (m3)	145.5	307.13	664.14
Length of access track (or floating road) (m)	418	6513	32490
Width of access track (or floating road) (m)	5.66	5.66	5.66
Average surface area of access track (m2)	2366	36,864	183,893
Floating road depth (m)*	0.53
Average volume of floating road (m3)*	1254
Length of hard standing (m)*	37.99
Width of hard standing (m)*	32.29
Average surface area of hard standing (m2)*	1226.7
Extend to drainage around drainage features at site (m)*	60
Average volume** of peat per turbine (m3) anticipated to be excavated (includes road network and cabling linking turbines to grid)	8060 (± 1464)	Average volume* per wind farm (m3)	328,446 (± 59,650)

*Independent of wind farm capacity (MW)

**Average taken from reviewed peatland management plans of operational wind farms in Scotland.

Case studies – Borrow pit reinstatement

To successfully reinstate peat within borrow pit excavations, it is important to consider the borrow pit location, hydrological connectivity, depth, vegetation cover, and to preserve the layering of the peat (Figure 2). It is best practice to reinstate the borrow pit profile to a comparative level to the surrounding landscape, with gentle slopes that blend into the landscape, it’s design should maintain hydrological connectivity with the wider environment whilst also holding water within the peat soil. Often “cells” are created within the borrow pit to enable easier reinstatement, these cells are sometimes lined with clay to reduce the permeability through to the underlying parent material. This is to enhance the hydrological connectivity of the reinstated borrow pit and aims to keep the area wet. However, an outflow is also needed so that the area doesn’t become permanently waterlogged (Figure d). It is assumed that natural regeneration of peatland vegetation will occur, therefore seeding is not usually part of the PMP, however if seeding were to occur this would usually be two years after construction as part of the planning conditions process.

a)	b)
c)	d)

e)

f)

Figure 2. Examples of borrow pits a) newly completed (< 1 year); b) in the process of being in-filled, one cell completed – cell wall construction (light coloured) and peat infill (dark coloured); c) 15-year old borrow pit with examples of functional peatland vegetation (from natural revegetation); d) 15-year old borrow pit that was not designed with drainage, has led to waterlogging (arrow indicates ponding); e) 10-year old borrow pit, quite dry, with more of an acidic grassland habitat; f) newly completed (< 1 year) situated on a slope, quite shallow peat.

Case studies – roadside verges / landscaping

Peat deposited alongside roadside verges often occurs more in terms of landscaping rather than for preservation of the peat (and carbon within it) (Figure 3). However, the volumes are relatively small compared to borrow pit reinstatement. If the peat does not become integrated with the surrounding hydrology, it will likely dry out and decompose over time, releasing CO₂ into the environment and possibly erode away.

a)	b)
c)	d)

Figure 3. Example of peat reused along roadside as part of landscaping process, a) drainage and indication of below ground cabling visible, vegetated peat reused for this infill; b) drainage channels and depth of floating road visible (newly constructed < 1 year), c) newly constructed (<1 year) landscaping, mixing of peat and mineral soil visible; d) Established peat at edge of floating road (15 years after construction), has maintained level and has peatland vegetation growing on it through natural revegetation. (Photographic permissions granted)

Case studies – incorporation within restoration projects

The reuse of peat is not considered for peatland restoration in the majority of cases. However, there are some examples where excavated peat has been used as part of the restoration process but this has only been permitted as an experimental approach. This is because once the peat is excavated (in the quantities it is being removed for wind farm construction), it has often lost structure and hydrological connectivity, and left as a stockpile until reinstatement begins (which varies from site to site).

Thus, the excavated peat has likely started to degrade, using this for restoration is unlikely to improve the habitat to the same level restoration with non-degraded peat would do. However, on some sites there are opportunities for reuse that could enable restoration if the appropriate planning and coordination between experts occurs. An example can be seen in Figure 4 (a and b). Key to the success of this kind of trial is planning how to implement it, for example a) efforts were made to move the peat only once – from excavation to reuse site; b) the layers of peat were kept separate and maintained across translocation; c) training was provided to the contractors involved in this reuse and restoration project. At a different site, excavated peat was used to infill peat cuttings that had occurred previously, however this infill can still be seen 10 years later (Figure 44c – differences in vegetation).

Although there are differences still visible in vegetation, the process for infilling used in situ vegetation. When reinstating the peat within the cuttings, the existing vegetation was stripped off and placed aside, the cuttings were then filled with acrotelmic peat generated from the excavation of nearby turbine bases. The vegetation was then replaced to reinstate the area and stabilise the peat. Although this may not have restored the peatland habitat to equivalent to undisturbed areas, as differences in vegetation are still visible. As the degradation was separate to wind farm construction, comparisons need to be made with how the environment was prior to wind farm construction, rather than comparison to pristine peatlands. Understanding whether the reuse of peat has been successful in maintaining a functioning peatland or at least preventing the loss of peat (and carbon) is very important, vegetation and water table monitoring occurs on some sites regularly to assess this (Figure 44d).

a)	b)
c)	d)

Figure 4. Examples of incorporation in restoration projects – a) Restoration trial (as part of the forest to bog project), where excavated peat was deposited at the side of a constructed track. However, to enhance restoration, prior to peat addition, vegetation was removed and the site ‘smoothed’, before the excavated peat was layered on top (to a depth of 150 mm or 300 mm dependent on trial site), after which the vegetation was put back on top of the reused peat. B) Zoomed in photo of trial site in a) peat vegetation covering trial site, with very little bare peat. C) Landscape restoration through the infill of furrows – here infill is within peat cuttings (but similar infill also occurs within the furrows of former forested sites). D) Dip well monitoring of water levels to assess success of peat reuse. (Photographic permissions granted)

Offsite use of excavated peat

Throughout this research it was discussed with stakeholders whether excavated peat could be used offsite from the wind farm construction; as to date only one paper was found. Balode et al., (2024) discussed various off-site novel uses for peat within the energy sector, building materials and additives, as well as agriculture and the wider environment (Figure 5); however, the paper does not focus solely on reuse and hence these uses are unlikely to occur within wind farm construction industry as the quantities involved in reuse are not going to warrant the creation of a comprehensive supply chain.

It is important to note that throughout the stakeholder consultation, it was repeatedly stated that reuse of peat off-site did not generally occur. Mainly this is due to two reasons, firstly classification – if the peat was taken off-site, it would be categorised as waste, which would likely entail a cost; secondly the necessary volumes of peat and the logistics of transportation would make it too costly to the project. If the reuse of peat offsite from wind farm construction was to be encouraged than new SEPA guidance and recommendations would need to be developed.

Figure 5. Novel applications of peat from Balode et al., (2024).

Environmental outcomes of peat reuse 

The results of the literature review indicates that all anthropogenic activities within a peatland will impact the fate of nutrients. The fluctuating water table, local geochemistry and hydrology are the main drivers of a peatlands’ groundwater chemistry and discharge (Monteverde et al., 2022). Wind farm construction can increase the fluvial macronutrient loading of catchment streams (Heal et al., 2020), however, forest felling has been shown to lead to greater dissolved organic carbon (DOC) within felled areas compared to wind farm catchments (Zheng et al., 2018). It is important to note that often wind farms are developed on felled forest sites that were previously peatland, e.g. Whitelees and Camster, however it has been calculated that nearly 14 million trees have been cut down as part of wind farm construction projects over the last 20 years (2000 – 2020)[1]. Thus, academic studies comparing habitats as if they are discrete categories like a felled forest compared to a wind farm development need to include previous land use as part of their analysis. In other words, undisturbed peatland to forestry to felled forest and windfarm may produce different results compared to an undisturbed peatland to wind farm, but if only considering the final use they would be classed as having the same management factors influencing them. It is also unclear whether the environmental perturbations are additive and would likely occur if the area hadn’t previously been changed? Also the timing of monitoring is important, for example a newly constructed wind farm showed 5 g m² losses in dissolved organic carbon (compared to control samples) over an 18-month period (Grieve and Gilvear, 2008) but it is unclear if losses reduce over time – this is a research gap. Is there an initial flush that quickly dissipates? Or are those losses continuous without signs of improvement. Grieve and Gilvear (2008) believe this 5 g m² loss represents between 25% and 50% of annual carbon sequestration in peatlands in central Scotland, so it is quite substantial.

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[1] https://www.heraldscotland.com/news/18270734.14m-trees-cut-scotland-make-way-wind-farms

The structure and hydrology of removed and replaced peat will not resemble that of the undisturbed peat and likely undergo further degradation through settlement and oxidation (Lindsay, 2018). Excavated peat is often used to blend the transition from undisturbed areas to those which are part of the construction. The disturbance to the peat results in negative impact to the habitat (Jorat et al., 2024), however using excavated peat to link undisturbed areas with disturbed areas will encourage vegetation regrowth in keeping with the surrounding landscape and may stablise the disturbed peat. Error! Reference source not found. provides an overview of the potential environmental outcomes for some of these reuse options.

Understanding how each reuse option impacts the wider environment will inform the hierarchy. Repowering of wind farms, upgrading the turbines and technology used within a wind farm site once it has reached the end of use-limit, is one method of reducing disturbance on peatland. However, this still requires extensive planning, as the newer turbines are often larger, needing different spacing between turbines and larger foundations. Approximately 30% more land surface area will be disturbed for repowering using a new rather than reengineered foundation (Waldron et al., 2018). If the surrounding peatland has not recovered from the previous development, this could lead to greater degradation than using new locations.

It is unsurprising that wind farm construction leads to wide-scale changes to the peatland habitat, which are known to be sensitive habitats with unique attributes related to their hydrology and carbon richness. Within this report we have been focused solely on the impact of wind farms on the excavation of peat and its reuse, however once in situ wind farms may still have an impact on the surrounding peatland. For example, a study by Moravec et al., (2018) showed that wind turbines can affect ground surface temperatures (which has the potential to change soil hydrology); and these changes varied with proximity to wind turbine (Armstrong et al., 2016). These impacts may also last for the lifetime of the wind farm, a large-scale review of the impacts of pipeline construction on soil and crops found that pipelines caused soil degradation for years and decades following installation and that soil compaction and soil horizon mixing detrimentally impacted soil function (Brehm and Culman, 2022).

Table 5: Synthesis of reuse options and simplified overview of potential environmental outcomes (Note: this table summarises potential outcomes indicated by research during this study, but evidence is limited and site-by-site circumstances vary significantly so currently this differentiation on environmental grounds cannot be fully reflected in the recommended ‘hierarchy of peat reuse’.)

Method of reuse	Carbon store	Hydrology connectivity	Availability	Comment
Borrow pit reinstatement	++ Low risk of carbon loss Low chance of carbon sequestration (carbon increase) in the long term	+ Only if well planned, with impermeable layers and outflows built in	+++ Large storage potential, should have capacity for all excavated peat, however where there is more (or less) peat than planned may lead to issues	Borrow pits have potential to provide an environmentally robust reuse option, however only if best practice is followed and there are contingencies in place if changes in planned volumes occur
Around turbine foundations and crane pad verges	— High risk of carbon loss through peat drying out and erosion	– When constructed these areas will automatically have drainage channels cut. The reuse of peat here will likely be impacted by this drainage	+ Small volume	Use to encourage vegetation re-growth around construction areas. Often used as a way of merging the built infrastructure with the surrounding landscape
Side of road/ track or “landscaping”	– Risk of carbon loss through peat drying out and erosion, however if vegetation regrowth occurs this is less likely	– Addition of peat should connect the reused peat with the wider environment to maintain hydrology, however, depends on flow patterns and drainage channels across roads	+ Small volume	If vegetation regrowth occurs and there is limited bare peat this has potential to become part of wider landscape
Incorporation of peat in restoration / reinstatement projects	+++ Low risk of carbon loss, has potential to build carbon (dependent on restoration / reuse project)	+++ If well planned, should have hydrological connectivity with landscape	+ Small volume	Usually these projects are highly monitored to assess progress – useful for data gathering in the short term alongside the benefits of using excavated peat in areas that may have been degraded previously

Limitations of data

Through the rapid evidence assessment (REA) we did not consider peatland restoration methods as part of the scope, however there are some strategies that go beyond restoration practices and should be a consideration as part of the reuse of peat. For example, rewetting peatland, drain blocking, revegetation, and fire management (Balode et al., 2024). Although there is academic research on the impact of peatland degradation, how wind farms can reduce reliance on fossil fuels and the social acceptance of wind farms within the environment, there is a lack of published research directly quantifying the impact of wind farms on peatlands, or providing evidence of best practice. Reliance on grey literature and stakeholder discussions is necessary to cover this research gap. For example, where novel reuse methods have been used, the industry has led monitoring of those sites, collected data and written these up as internal reports, which are not obviously available for the wider industry and academia to use. However, “standard practice” is rarely reviewed in academia nor comprehensive data collected, thus it is very difficult to make recommendations on what works best through standard literature reviews. Grey literature may be written with bias, there may be a lack of replication within the data, and it will not have been peer reviewed and is thus less reliable as a data source.

Often there is limited detail within peat management plans and planning applications for wind farms. For example, it is assumed that all excavated material will be peat; differences between peat layers (acrotelm and catotelm) are not distinguished and there is no reference to the vegetation layer. Depending on volumes, the only indication of reuse is stated as backfilling around turbine bases and landscaping around access tracks. As well as the aforementioned issues with the reuse of excavated peat, one important consideration that is often not discussed is that the different layers of peat excavated (acrotelm and catotelm) have different physical properties. Whilst the reuse options discussed above may be appropriate for acrotelm peat, they are unlikely to be suitable for catotelmic peat (generally below 1m depth peat)[1].

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[1] https://www.sepa.org.uk/media/287064/wst-g-052-developments-on-peat-and-off-site-uses-of-waste-peat.pdf

Knowledge and evidence gaps

There is a lack of understanding related to the outcome of peat reuse – is it to restore peatland bog function, or is it to try to reduce losses of carbon from the excavated peat? Or is it to do something with the excavated peat that will minimally impact the wider environment? The likelihood is that the overall outcome will be somewhere between these points.

Although there is a significant amount of academic research on the impact of wind farms on peatland, there were clear gaps related to what should be deemed ‘best practice’. For example, there is no published work on the measurement of peatland parameters as part of the reinstatement of borrow pits on wind farms – how can best practice be defined when there is no indication of something working in practice, or a clear understanding of what ‘success’ looks like in this context? There have also not been any in-depth assessments of carbon loss after excavation and reuse – discussions were held in relation to loss of carbon as the peat dried out, but there is a lack of direct studies focusing on this over time. This information is also absent from the grey literature. There was a lot of discussion with stakeholders regarding what they believe works best from a real-world perspective (rather than lab based academic studies), but this still lacked underlying reported evidence, and was only discussed in terms of past experience of what worked (to reuse the peat available, and perceived that it remained within the field rather than eroding) and what hasn’t worked, remaining largely unmeasured and therefore unproven. Interestingly, where a wind farm had used a novel method of reuse, there was a monitoring plan set up by the energy company and evidence was gathered to justify this method. Highlighting how energy companies can lead the way in providing evidence of good practice.

Generally, there was a lack of monitoring occurring, both in terms of whether the construction process adheres to what has been set out in the PMPs but also to ascertain whether the approach has worked (and thus could be referred back to and repeated elsewhere). There is also a disconnect between the desired outcomes compared to the aims of the wind farm operators. For the wind farm developers, there is a need to balance aspects such as effectiveness and safety within the construction process (i.e. the need for drainage), with restoration, when that part of the construction process is complete. Removing drainage if it is no longer necessary within the wind farm infrastructure would enable an area to return to a more natural peatland habitat, although dialogue is required to ensure a shared understanding of how this might be defined.

Legislation and advisory documents change over time, for example “Scotland’s Peatland Standard”[1] (SPS) is currently being developed. This document will provide technical information and guidance to promote peatland protection. It will define the minimum for sustainable management and restoration requirements that Scottish Government expects all peatland owners, managers and contactors to follow. Thus, in future could potentially fill some of these knowledge gaps discussed.

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[1] https://www.nature.scot/climate-change/nature-based-solutions/nature-based-solutions-practice/peatland-action/peatland-action-how-do-i-restore-and-manage-my-peatland-0

Recommendations

We have developed the hierarchy below for reuse of peat through the literature review, stakeholder discussions and site visits presented within this report. We considered the role and nature of a potential hierarchy for peat reuse methods during this project, considering:

• What needs to be included in a hierarchy and in which order.
• What additional guidance or principles would help guide an environmentally beneficial approach to peat reuse.
• Highlighting the research gaps at this time that need to be addressed to better inform a hierarchy of peat reuse methods.

Based on the findings of this study we have three recommendations:

Recommendation 1: Guidance on excavation peat reuse

1a: Planning and preparation steps
1b: A draft hierarchy of reuse methods
1c: Peat reuse and implementation principles

Recommendation 2: Environmental outcomes framework to ensure the multiple potential environmental benefits of peat reuse are considered, avoiding a single-issue focus.

Recommendation 3: Enhanced monitoring of environmental outcomes from reuse of peat – these investigations need to be targeted to address the specific research gaps highlighted in our study, and also better routine monitoring of site reuse implementation and environmental outcomes.

Our recommendations come from learnings acquired during this study. Through a rapid evidence assessment, an understanding was gained of the current research occurring on peatlands and wind farm developments, alongside site visits to see what was occurring in the field and a series of stakeholder discussions and workshops to fill in the gaps where reports or data were lacking. An area of clear agreement across stakeholders, both in terms of construction and also the conservation sector, is to minimise the amount of peat excavated. Avoidance of peat excavation can mean different things to different stakeholders, for example:

• Is avoidance about minimising the volume of peat excavated? (reduction of waste and minimising cost) – Yes
• Is avoidance about minimising the areas of carbon-rich soil impacted by excavation? (limited footprint of impact) – Yes
• Is avoidance about minimising the loss of area of peatland in pristine / good conditions? (protected biodiversity) – Yes
• Is avoidance about minimising loss of hydrological connectivity across on-site/off-site peatland and the wider functions of larger peat bodies? (ecosystem services) – Yes

Depending on the perspective of the stakeholder they may agree or disagree with some of the above statements, however they are overlapping in terms of reducing the impact of wind farm construction across peatlands. Avoidance is the essential first step in the hierarchy of reuse.

At times the timeline between site acquirement, site surveys, planning approval, and construction company deployment, leads to issues related to preparation and planning. Discussion with stakeholders highlighted that often the site surveys presented as part of the planning applications may not be at the detailed scale necessary to identify areas with the deepest peat (that should be avoided) at the construction stage. The construction contractors would like to avoid the areas with the deepest peat (due to costs and time, as well as to minimise the amount of peat disturbed) but are limited by what has previously been set out within the planning application. The condition of the existing peatland across the landscape prior to wind farm construction may not have been fully assessed, thus if the peat is already degraded the starting point for the reuse of peat will be lower and has the potential to degrade faster when disturbed.

Understanding the hydrological connectivity of the landscape will enable appropriate placement of drainage, this links closely to site condition – if there are already drier areas within the peatland, they may become drier over time with increased drainage. In some instances it is possible to reduce drainage after construction, if the areas being drained are reinstated with peat, however this is a consideration that should be made at the planning stage. Greater training needs to be provided for the construction operatives, both in terms of implementation of activities, but also to understand why it is important; as key to maintaining the quality of the peat during reuse, is minimising disturbance and maintaining the peat structure from the outset.

The importance of peatland for carbon storage is widely discussed both within the literature and by stakeholders, however, a key disconnection between the planning process and the completion of windfarm construction is the accuracy of the carbon calculations – it was widely discussed that in the majority of developments more peat is excavated than was planned. The actual amount of excavated peat is not used to recalculate the carbon loss and thus the overall impact of the wind farm development is not fully assessed. It also means the contractors inevitably have more peat excavated than was planned for reuse, thus the options for reuse of this peat may lack adequate planning for how to reuse appropriately. It is a pity contractors aren’t required to report how much peat has been excavated during the construction process, as this could improve the accuracy of estimates over time, but currently this data is not available or monitored. The condition of the peat that is reused is rarely monitored (at excavation or afterwards), therefore it is unclear whether this peat will continue storing the carbon it contains or whether carbon will be released into the atmosphere. Academic studies collecting empirical data on the release of carbon from disturbed peat are rare, and do not occur at a field scale or if they do these assessments usually occur in relation to agricultural disturbance rather than windfarm construction and are not wholly applicable. Where the peat was excavated from is also an important consideration for reuse – if it is taken from a borrow pit excavation this lends itself to borrow pit reinstatement, however if it is removed for cabling and road installation than returning the peat to this area (referred to as landscaping) may be a better option.

Recommendation 1: Guidance for Peat Reuse Options

Because detailed evidence to confirm the different environmental outcomes is not available, our recommendation is for a simple hierarchy of peat reuse options accompanied by some additional guidance and requirements which are essential for maximising environmental outcomes:

• Recommendation 1a: Preparation and Planning Steps:
• Avoiding / minimising peat excavation and
• Appraise site circumstances and locally relevant potential reuse options
• Recommendation 1b: Hierarchy of Peat Reuse
• Recommendation 1c: Peat Reuse Implementation Principles: to guide the site-specific choice of methods and implementation to maximise environmental outcomes.

The hierarchy is not useable as a standalone guide – it must be accompanied by the additional components – as shown in

.

Figure 6: Guidance for Excavated Peat Reuse

 

Recommendation 1a: Preparation and planning steps

Is critical to conduct investigations to inform preparation and planning in order to maximise environmental outcomes – including first taking action to avoid peat extraction. Our recommended preparation and planning steps are set out in Table 6.

Table 6: Preparation and planning steps to accompany the hierarchy of peat reuse

Step 1: Avoidance
As per NPF4, avoidance of peat excavation is always the priority, in agreement with the NPF4 mitigation hierarchy. As part of the avoidance strategy, a “restorability assessment” should also be included – this should determine the condition of any peat that is due to be excavated and makes an assessment of the potential for reinstating the peat in that location. Taking into account the peatland condition, where it is located within the wider landscape, accessibility and how easy it may be to restore degradation in the future. As part of the avoidance strategy, as well as macro-level site decisions (e.g. develop on peat or not), micro-level decisions on site and in project designing and contracting should be considered to reduce the volume of peat excavated and/or impacted. For example, ensuring peat depth assessments are accurate and are used to guide any micro-siting[1] decisions. [1] Micro-siting is where small adjustments to the wind farm lay out are made to avoid / minimise damage to peat (or other sensitive environments) on site.
Step 2: Preparation and planning: Appraise site and potential reuse outcomes
Preparation is critical for identifying the most beneficial options available on site and their feasibility. What is the depth of peat across the site? What has the peat been categorised as? If it is not in good condition, does it have potential for restoration? Has it been modified? Or drained? Aligning the details submitted within the application process (EIA) with further surveys, identifying depth and condition of peat at the exact locations for the tracks, turbines, general infrastructure and proposed reuse locations. Planning, with the desired outcome in mind, is crucial to the successful reuse of peat. Knowing the volumes of peat to be excavated and from where on the site. Knowing the depth of peat and the thickness of each layer (acrotelm and catotelm). Planning where the borrow pit and stockpile need to be located. Planning peat movements to minimise disturbance. Contacting other stakeholders that may be able to enhance reuse of peat activities.
Prior land use:	Understanding what the starting land condition is. Has the land been used for other activities prior to wind farm planning? For example, many wind farms are being built on previous forest sites; some may have been used for grazing or are semi-natural habitats? These previous activities will impact drainage across the site, some areas may be drier or need to have the drained area restored, stump flipping may need to occur, and also natural regeneration of forest may affect the vegetative composition.
Peat condition and depth:	If the peat is in “good” condition prior to wind farm construction, this may negate some of the energy savings of renewable energy generation, as some studies have suggested that the carbon saved from the wind farm development won’t offset the damage to the environment. However, there are very few areas of pristine peatland in Scotland, and it is more likely to be a mosaic of conditions across the landscape – which may need to be considered regarding the progress of construction. The depth of peat in the area is also important, as deeper peats have different properties in terms of acrotelm, catotelm and underlying parent material. Very shallow peats are also a concern as they are more liable to mixing of soil and peat layers.
Reusability of peat at start of construction	The condition of peat prior to excavation will have an impact on its reusability. If the surrounding peatland is degraded, reused peat is unlikely to improve the conditions in the surrounding area (unlike peat extracted for restoration purposes). Inevitably, there will always be some degradation as peat is excavated (whether that’s through a loss of carbon or changes in porosity, hydrology, or vegetation coverage); thus minimising the amount of peat excavated will protect the environment. However, the counter point is that if the peat excavated is in very poor condition to begin with, it may not be able to be reused, and perhaps should not be excavated?
Site specific opportunities for reuse:	For all wind farms (and construction sites), the geographic limits for development activities are set (the development envelope). If there are areas where the reuse of peat would be more appropriate that is outside this area, than the reuse cannot occur there. Consideration should also be given to the site layout and options for reuse destinations – what is being constructed first and where. For example, the floating roads are often the first part of the infrastructure constructed to allow access to all areas. Where are the water courses and flows within the site, what is the connectivity with the wider landscape and habitats e.g. Is there an overlap with prior landuse or adjacent restoration work? Is the order of excavation and reuse appropriate to minimise carbon loss?
Agree desired outcome for use of excavated peat:	Setting a feasible intention (e.g. habitat to aim for) considering the site conditions and opportunities at the outset.

Recommendation 1b: Hierarchy of reuse

The rational for the hierarchy of reuse set out in Table 7 reflects the available evidence for environmental outcomes of peat reuse. The main options all have potential to deliver positive environmental outcomes in comparison to the secondary options or landfilling but there is insufficient evidence to rank the main options further. Their feasibility and environmental outcomes will depend upon the site context and the way they are implemented.

The table provides a supplement to the available information on good practices for use and handling of soil and peat. The evidence of environmental outcomes of reuse options has many gaps currently. Where there is evidence, it cannot always be confidently applied to specific sites and circumstances. Therefore, these principles / considerations are taking the precautionary principal approach and should be used as stepping stones reflecting the consensus amongst technical experts about things which are important to consider in the absence of a complete evidence base.

Table 7: Underlying rationale and details related to hierarchy of reuse of peat

(1) Main re-use options
Borrow pit reinstatement or infill	Borrow pit reinstatement involves putting excavated peat into a borrow pit at the end of the period of use. Potential desired outcomes can vary and should be informed by the planning steps. Key priorities: Aim for a functioning bog, then consider other locally valuable habitats. Management / design needs to prioritise setting up the reinstated borrow pit appropriately for desired outcomes e.g. including an impermeable layer at the bottom of the pit; water outlet to hydrologically link the borrow pit to the rest of the peatland habitat; layered in a similar way to how it was excavated (including a vegetation layer). Aim to only move peat once if possible. Otherwise, if the peat that is removed from the borrow pit will be returned to the borrow pit it will need to be stockpiled prior to reuse. Reinstating the surface vegetation appropriately should enable recolonisation of the surface layer which will aid the development of a functioning bog habitat and increase biodiversity. Rationale: Capable of taking high volume, of which a significant portion may be from the original site as a result of the borrow pit excavation. Whilst our study did not find peer reviewed studies that confirmed the environmental outcomes of borrow pit reinstatement, observations and comments from stakeholders, and their in-progress monitoring suggests some good environmental outcomes (including maintaining water levels and peatland vegetation), when borrow pit reinstatement is completed properly following the above key priorities. Further research is needed to confirm these environmental outcomes – we have seen this is occurring at some sites, it would be beneficial to the sector if these results were published.
Other reinstatement	There are other areas impacted by wind farm developments that could be consider for reinstatement – for example areas that have been used for building compounds, crane pads, temporary access tracks etc Reinstatement involves the reuse of peat to blend the natural habitat with the infrastructure disturbance as a way to encourage vegetation re-growth. Key priorities: Maintaining hydrological connectivity between the reuse of peat and the landscape in situ. High risk of the peat drying out leading to erosion. To reduce this risk it is important to follow the peatland restoration technical compendium and future requirements of the forthcoming Scotland Peatland Standard.
Restoration	Restoration involves the reuse of excavated peat by incorporating it into areas of peatland on site that have previously been degraded through anthropogenic activities – for example forestry or peat-cuttings directly accessible from the development site. This can offset (compensate) for some of the residual impact of the development or for enhancing peatland conditions in support of the reinstatement of functional peatland. A number of discussions with stakeholders presented examples of this type of restoration occurring on wind farm developments. Although the results are unpublished, the results show promise as a way of delivering enhanced environmental benefits as part of the construction process. Key priorities: Design must be site specific aiming for functioning peatland or other locally valuable habitat. After a thorough site survey, areas that are degraded peat should be identified and considered part of the reuse process. For long term success of this reuse method there needs to be collaboration between peatland restoration experts alongside the construction sector and use of the peatland restoration technical compendium alongside the Scotland Peatland Standard. Rationale: If this method of reuse of excavated peat was to occur, it would initially only be in areas within the wind farm development site identified as potential areas for restoration. Reusing peat in these areas, although takes more planning and time (including assessing peat slide risks), is likely to be beneficial, particularly if it enables restoration which would not be possible in the absence of available peat. Reinstating peat where peat has been historically located has a greater likelihood of returning peat to a functioning level than reusing peat in areas that were not peatland previously. Peer reviewed studies were not available to confirm environmental outcomes of peat in restoration but observations and comments from stakeholders, and their in-progress monitoring suggests potential for good environmental outcomes, although only if well designed – more research is needed to understand effective methods and environmental outcomes.
Landscaping (road verges, embankment slopes etc)	Landscaping involves reinstatement of peat above cabling and alongside floating roads and embankments. Often the excavated peat is from where the cable is to be laid and will be returned to where it was extracted from, however alongside roads and embankments may be from other areas. Key priorities: Care needs to be taken to maintain peat layering and planning related to hydrology needs to occur (as the peat above the cable risks being hydrologically isolated if situated between the floating road and drainage channels). Floating roads are often higher than the surrounding habitat, as aggregate and geotextile mesh has been put down as part of the construction process, this creates an island effect. It is important to consider the vegetation when reusing peat as part of the landscaping process. It is crucial to not reinstate peat on top of vegetation, this may mean that vegetation needs to be lifted away to reuse peat prior to returning the vegetation to the area. Rationale: Reusing peat along these road verges can improve the landscape, by changing the levels between the road and the wider landscape reducing the risk of island effects, but only if the hydrology and placement is considered, will it have the potential to reduce degradation. It may be the only practical option in some circumstances as blending the zones between the infrastructure and wider environment may reduce the degradation spreading into the undisturbed peatland (through reducing the risk of the peat drying out and erosion occurring). Reinstating excavated peat along the roadside will stabilise the surface and reduce the sediment runoff which could damage the wider environment. Reusing excavated peat along roadsides gives the natural vegetation a chance to recolonise and restore these areas close to the wind farm development. Vegetation reduces the risk of erosion and further degradation.
Secondary options (2,3)
There is limited interest in reusing peat offsite and for the majority of construction projects it does not appear to occur. Questions were asked of stakeholders to assess if excavated peat could be reused within the horticulture sector, whisky industry or other aspects of the construction or energy sector. In all instances the answer was a definitive no, there is no evidence for the reuse of peat offsite in these sectors as part of wind farm construction, it does not occur. This is likely due to the volumes of peat involved and the sporadic nature of the supply chain, also as the Scottish Government has committed to phasing out the use of peat in horticulture this is unlikely to gain momentum as a viable option. There are instances where an area has lost peat previously due to land use activities and offers an opportunity for excavated peat to be reused as part of restoration. An example from the stakeholder consultation was where the reuse of peat from a wind farm construction was used to reinstate an area of mining that had occurred nearby. It is important to note that if onsite reuse cannot occur all endeavours should be made to undertake these secondary options prior to the last option of landfill which should be avoided.
(2) Offsite (known use)		This reuse occurs on a case-by-case basis and usually occurs where the land ownership or construction operators are linked. For it to occur more frequently, greater planning and preparation needs to be implemented prior to excavation and transport.
(3) Offsite (unknown use)		Where peat has been extracted and there was no reuse plan in place for it, this could lead to unknown use offsite. This reuse is very unlikely to occur but when it does it is usually in small quantities e.g. for novel trials of reuse options. This is because once peat leaves the site it will be considered waste and is also costly to transport.
(4) Last resort option
Landfill		This should be considered a “last resort” option, and all other options should be prioritised before this.

Recommendation 1c: Peat Reuse Implementation Principles

The effectiveness and likely outcomes of different methods of peat reuse is heavily dependent on-site specific context, feasibility of achieving the desired outcome, and the detailed design of the method (such as borrow pit infill design). Thus, any hierarchy needs to be flexible, but decisions should be guided by a set of principles to maximise environmental outcomes. These include:

• Aiming for functioning peatland (as close to natural functioning as possible because full natural functioning is likely to be unachievable in most cases), or other valuable habitat if not possible.
• Maintaining / reinstating vegetation
• Maintaining / reinstating water flows / hydrological functioning, whilst ensuring site stability and safety.
• Minimising peat movement
• Maintain peat structure (layers) where possible.

See Table 8 below for more detail.

Putting these into practice is facilitated by the preparation steps set out in Recommendation 1a above. For example greater detail could be requested prior to planning consent, because most peatland management plans lack depth and site-specific details. Requiring this information prior to the start of the construction process will increase the likelihood that planning, and preparation will be undertaken to the necessary extent to improve the outcomes of peat reuse. This would move the onus from contractor and place it with the energy company / landowner that ‘owns’ the consent and is responsible for full legal compliance. Greater detail within the PMPs would also provide a more accurate understanding of the true quantities of peat to be excavated, by including a requirement under the consent for accurate recording and in turn enhance the reuse strategy to be implemented. This could also provide future developments with more accurate calculations to use within their planning applications and PMPs. However, it is beyond the scope of this research to identify where responsibility lies for receiving and reviewing such additional material.

It was clear through the stakeholder consultation that there are a number of very knowledgeable groups working within the sector (Appendix B, including environmental government organisations, wind farm contractors, energy companies, environmental consultants from the private sector, as well as academics and conservation organisations). Capturing this knowledge to ensure recommendations for best practice are supported by what is practical will improve the wind farm construction process in the future.

Table 8: Peat reuse implementation principles – further explanation

Peat reuse implementation principles
Hydrological connectivity	Mapping out the connectivity of the site, will enable better drainage planning, targeted to ensure site stability / safety and support the desired peat reuse goal e.g., desired habitat. It will also enable more successful reuse of the peat if it is kept wet and can connect into the hydrology of the surrounding land at the location of reuse.
Minimise peat handling and disturbance	If enough planning has occurred, it may be possible to only need to move the peat once – from where it is excavated to the site of reuse. This also avoids storage of excavated peat, which generally leads to undesirable changes in peat properties, e.g. loss of water, bulk density increase, carbon loss, damage to microbial populations
Separation of peat layers	When excavating peat, the success of reuse will be increased if the different peat layers are kept separate (acrotelm, catotelm, and underlying mineral soil) as they have very different properties.
Maintain wetness of stockpiles	Stockpiling of excavated peat should be avoided where possible. If necessary to stockpile peat, stockpiles should be watered when necessary to maintain wetness. If the surface of peat dries out, a hydrophobic layer may form. This reduces the overall infiltration rate of the peat blocks and may lead to further desiccation and other negative impacts, as noted above under ‘Minimise disturbance and avoid storage/stockpiling’.

Recommendation 2: Environmental outcomes framework

Multiple environmental outcomes should be targeted through peat reuse. To avoid excessive focus on one environmental measure of success, we recommend the following environmental outcomes should be considered when deciding on which peat reuse option to implement on site. These environmental outcomes should be monitored to assess success (see Table 9 for rationale):

• Minimising carbon loss from excavated peat
• Positive biodiversity outcomes reflecting local and national goals
• Ensuring downstream water quality (sediment / nutrient load)

Following on from Recommendation 1 and the hierarchy of reuse options, environmental outcomes framework indicates the priority environmental outcomes for peat reuse. These should be considered by the consenting authority as part of the planning process, in conjunction with the EIA process and developers should be considering these in their development plans. We recommend the consenting authority to check that the applicant has fully considered these areas within the planning proposal as part of their strategy for reuse. The environmental outcomes framework should also guide subsequent monitoring and evaluation, during and after construction. Clarity on what environmental outcomes could potentially be achieved from peat reuse can support all parties to deliver better environmental outcomes.

Table 9: Rationale for Environmental Outcomes Framework for Peat Reuse

Outcome	Rationale for inclusion in the Framework
Minimising carbon loss from excavated peat	Carbon can be lost as the peat is disturbed primarily through hydrological changes and erosion – these two processes are interlinked, as erosion is more likely when peat starts to dry out. Leading to the loss of particulate organic carbon (POC) which is more easily transported by wind or water erosion. As the peat dries out and is exposed to oxygen, aerobic decomposition of the organic matter starts to occur, releasing the stored carbon as CO2. As carbon is lost subsidence of the peatland may also occur, this has knock-on concerns for the wider environment and safety and stability of the wind farm. Where the excavated peat has been left bare of vegetation carbon loss and erosion are also a greater risk.
Positive biodiversity outcomes reflecting local and national goals	Enabling the regrowth of peatland vegetation (particularly indicative peatland species like sphagnum mosses) helps rebuild peat structure and enhances carbon sequestration potential, but it also improves the wider biodiversity within the environment. However, studies focusing on peatland restoration have shown that vegetation is slow to recover and even ten years after restoration the vegetation present can still be dissimilar to pristine peatlands (Kareksela et al., 2015). Thus greater consideration is necessary related to vegetation regrowth to maximise its potential. Within our recommendations we have advised on best practice for the reuse of peat, however action should also be taken to maintain vegetative cover alongside this reuse. Whether this is through moving the vegetation layer as part of the reinstatement of reused peat, seeding the reused peat, or if there is existing vegetation in the area planned for peat reuse, stripping this off and placing aside, so that the vegetation can be replaced once the reused peat is reinstated in the area and stabilise the peat.
Ensuring downstream water quality (sediment / nutrient load)	Excavated peat can lead to increases in dissolved organic carbon (DOC) within water systems leading to changes in downstream water quality, as well as increased sediment loads. This can be through the physical disturbance of the construction process increasing water erosion and DOC leaching. Drainage can cause hydrological alterations and redirect water flows, mobilising sediments (POC) and DOC leading to increased carbon losses and peatland erosion (Grieve & Gilvear, 2008).

Recommendation 3: Improved research and monitoring

In discussion with stakeholders, some monitoring is occurring post wind farm construction for peat reuse, usually by the landowner or energy company, however as discussed previously this monitoring is not mandatory and usually focuses on novel uses, or where the reuse appears to have been successful. We recommend:

• Monitoring of environmental outcomes of peat reuse for the life of the windfarm, EIAs often require follow up monitoring in relation to biodiversity post-construction, however Peatland Management Plans (PMPs) do not. We recommend greater considerations is given to PMPs as part of follow up monitoring to include:
• Monitoring of peat levels, and wetness around the wind farm, irrespective of reuse option, this should occur to identify areas that may be drying out due to drainage, or where too much waterlogging may be occurring because of the changes in hydrology caused by the construction process.
• Monitoring of vegetation cover and types, for example through vegetation surveys are used as indications of functioning peatlands, but other measures (like DOC within the water catchment or carbon fluxes) could provide a more nuanced understanding of the impact reuse is having on the wider environment.
• Greater sharing of this data and collaboration with the academic community, would also enable further distinctions of best practice to occur. We recommend a formal advisory relationship to form between developers and the research community facilitated by Scottish Government, so that data sharing can occur and consenting authorities have access to better knowledge of effective peat reuse being undertaken. Data that has historically been collected but has not been reported on could be shared initially to assess how a collaborative data sharing process may work. The current lack of data sharing and credible longitudinal studies was noticeable at the site visits for wind farms that had been commissioned 10+ years previously – key details had been lost with job changes / retirement that could have benefitted the wind farm sector as a whole, with improved understanding of what is now visibly working and what hasn’t worked so well.

Research gaps

There are many research gaps that have been highlighted throughout this study. These could be addressed through the following actions:

• The exact volume of peat excavated across a wind farm development is not known at completion of construction → We recommend asking the contractors to update records at the end of construction. Building on this we recommend a study to assess the differences between the amount of peat stated to be extracted prior to the wind farm development commencing compared to the wind farm after construction has finished. This could also be used to improve the accuracy of the carbon calculator providing a more accurate picture of the true carbon losses after completion of construction.
• Understanding how the carbon content changes within the peat volume over time for all reuse options → We recommend monitoring projects focusing on carbon loss and GHG emissions
• Seeing how the full GHG balance for infilled borrow pits changes dependent on size and age of the borrowpit → We recommend that monitoring of infilled borrow pits including size and volume, and hydro connectivity needs to occur at regular intervals
• The environmental outcomes of borrow pits have not been fully assessed → We recommend collecting monitoring data of the regeneration of plants and biodiversity over time will enable this.
• Reviewing available printed information on best practice (and standard practice) → Likely this is very limited and may involve contacting energy companies to access internal data and reports. We recommend greater collaboration between the energy companies and academia, with a greater amount of data sharing. Funding opportunities are usually the best way to encourage engagement between different stakeholders.
• The level of revegetation on peat that had previously been excavated appears to be reliant on natural recolonisation, how well this occurs is not thoroughly understood. → We recommend monitoring how plants recolonise the excavated peat that has been reused which would enable a better understanding of best practice. From discussions with stakeholders there is limited reseeding occurring and it is largely left to natural revegetation. However, this is more likely to occur if the surface plants are maintained (removing the in situ plants, redistributing the reused peat and returning the plants on top should enhance recolonisation rates).

Conclusions

These results highlight our current understanding of peat reuse methods occurring in wind farm construction in Scotland. We have identified the critical environmental issues and how the reuse of peat can maintain the habitat, allowing for environmentally conscious construction techniques to take precedence.

However, the overriding synthesis of the information gained during this process is that planning prior to construction is key, as well as ensuring that stakeholders work together to achieve best practice. Avoidance of excavation of deep peat is the first priority. Next, acknowledging that once peat is excavated full consideration of how best to reuse it (ideally only moving it once and keeping the different layers separate, while aiming to keep the peat wet and/or maintaining hydrological connectivity) are crucial.

After these main outcomes from the hierarchy, attention needs to focus on delivering site specific reuse. It also became apparent that although there is a lot of knowledge within the peatland and wind farm sector, there has been limited studies collecting data to inform best practice. This needs to be encouraged to understand current research gaps and advise on the right management methods to reduce peatland degradation in the long term.

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Appendix A – Research scope, questions and methods

Research Scope and Questions

To provide a comprehensive overview of the current state of knowledge, identify key knowledge gaps, and highlight areas for future research and policy development in sustainable peatland management within the context of renewable energy infrastructure, particularly in Scotland, this review has centred on the below questions:

Current practices:

• How are excavated peat management and reuse practices being employed (of relevance for Scottish wind farm developments) both on-site and off-site?

Environmental impacts of current methods:

• What are the impacts and/or benefits of current peat reuse practices in relation to hydrology and water quality, carbon emissions and storage, biodiversity and habitats?
• Are there any environmental risks associated with current peat reuse practices, such as increased sediment load, erosion or landscape instability?
• How do impacts change over time – what timeframes are relevant and are there long-term impacts of peatland disturbance and reuse practices?

Limitations and challenges:

• What are the technical limitations of using excavated peat on-site?
• How do regulatory frameworks impact the options for peat reuse?

Best practices:

• From current available evidence, what peat reuse practices are preferable for minimising GHG emissions and wider negative environmental impacts?
• How can peat management plans be optimised to maximise environmental benefits and minimise carbon losses?

Development of a reuse hierarchy

• Hierarchy of Peat Reuse
• Preparation and Planning Steps
• Peat Reuse Implementation Principles

Research Methods

The following sections describe the information collation methods and data sources used in this study, these methods have been kept purposefully brief here, for more detail please see the appendices. A project database was compiled in Excel and is supplied separately to this project report.

Rapid Evidence Assessment

The method used for performing the evidence review was based on the Natural England (2013) evidence review methodology to ensure that the approach was transparent, objective and rigorous, allowing for robust evidential conclusions to be drawn from the available information for a full description see Appendix A.

Rapid Evidence Assessment methodology

The method used for performing the evidence review was based on the Natural England (2013) evidence review methodology to ensure that the approach was transparent, objective and rigorous, allowing for robust evidential conclusions to be drawn from the available information.

Scope

This rapid evidence assessment (REA) focused on synthesizing current evidence related to peatland excavation and reuse within the context of wind farm construction and similar large-scale developments. The assessment covered:

• Current standard practices of peatland excavation and management in development projects.
• Environmental impacts of peatland disturbance.
• Opportunities for reuse of excavated peat on-site and off-site, including their environmental benefits and limitations over different timescales
• Best practices for minimizing peatland disturbance and optimizing peat management plans.

Evidence search approach

The methodology comprises five main steps:

• Define search strategy including keyword list compilation and define inclusion/exclusion criteria.
• Searching for evidence and record findings.
• Title and abstract screen.
• Evidence extraction.
• Evidence synthesis and evidence gap identification.

Step 1: Keyword list compilation

To establish a systematic search strategy, a list of key search words, search terms and suitable combinations were developed (included in separately shared document). These search terms were recorded for systematic use by the review team to reduce bias.

Step 2: Identification of information sources

In order to develop a comprehensive and relevant evidence base, appropriate information sources were identified. To reduce the risk of publication bias on the evidence base a range of information sources were used, which enabled access to peer-reviewed literature, grey-literature, and unpublished sources.

For this review Science Direct and Scopus were used to identify peer-reviewed information. Google Scholar and Research Gate provided further access to peer-reviewed information to enhance the literature search. Grey literature was also identified in the search and included industry reports and relevant committee proceedings.

Step 3: Evidence search

To facilitate the repeatability and transparency of the search process evidence searches were carried out as Boolean searches (AND, OR, NOT, etc). For example, using Boolean operators we searched (“excavated peat” OR “peatlands” OR “peat bogs” OR “carbon rich soils”) AND (“reuse” OR “recycling” OR “repurposing” OR “reclamation” OR “displaced” OR “borrow pits”) AND (“wind farms” OR “wind turbines” OR “wind energy” OR “onshore wind” OR “renewable energy”) AND (“sustainability” OR “environmental impact” OR “eco-friendly” OR “carbon footprint” OR “climate change” OR “carbon flux” OR “soil restoration” OR “land rehabilitation” OR “habitat restoration” OR “conservation”). The results of each search were recorded, including the number of search hits and number of relevant records returned, date of search and database used. Any other sources, such as evidence provided by stakeholders or generated through stakeholder engagement meetings were also documented similarly.

Developing and establishing search strings was treated as an iterative process and, as such, search strings were amended or adapted to optimise search relevance particularly where the number of search hits or relevance of records retrieved are excessively large or small.

Step 4: Title and abstract screen

In order to allow for a systematic and repeatable approach to screening whilst minimising individual subjectivity and bias, results of the evidence search were screened by title and abstract against pre-established inclusion and exclusion criteria for the review question(s). Evidence that did not satisfy the inclusion criteria were not taken forward for further analysis. References and key details (search date, search terms, publication name, database source and a DOI) were captured for all selected literature. Duplicates are also removed at this stage.

Step 5: Evidence extraction

To allow for interpretation and evaluation of the available literature evidence. A consistent, systematic approach to extracting evidence was taken for each item in the evidence item. Information was extracted on the basis of the review questions. Collated information included details of the type of study, the situation studied, key outcomes, endpoints and geographical extent (reported in separately shared excel document).

Step 6: Evidence synthesis and evidence gap identification

The compilation of evidence allowed for the type and amount of evidence obtained to be scrutinised and for any key evidence gaps or conversely areas of extensive evidence to be highlighted. This allowed for conclusions to be drawn based on the findings review and further enabled the appraisal of whether the collated evidence was adequate and suitable for addressing the review question. The collated information from the review of the literature is detailed in Supplementary Document 1 (finalisation in process).

Availability of the literature

The Rapid Evidence Assessment methodology used (Appendix A) obtained over 250 articles and reports through a range of keyword searches, in Science Direct and Google Scholar as described above. These were screened based on their title and abstract to identify relevant articles. This resulted in 50 articles and reports that were flagged as relevant for further scrutiny. These articles were then reviewed, and key information was extracted and is included within this report.

Desk-based research into current practices

A list of current wind farms in Scotland was obtained from the renewable energy planning database^[12] (October 2024, quarter 3) sorted by energy type, location and whether they were currently operational (Figure 7). A sample of wind farms were chosen (as examples of a range of sizes of wind farms and locations across Scotland), to review the information provided within the peatland management plans, amount of peat to be excavated (if stated within application) and other related environmental planning information where obtained.

Figure 7. The distribution of wind farms across Scotland with peatland also highlighted. A list of current wind farms in Scotland was obtained from the renewable energy planning database^[13] (October 2024, quarter 3) sorted by energy type, location and whether they were currently operational these were plotted on to a map of Scotland along with the distribution of peatland taken from Carbon and Peatland 2016 map^[14].

Site visits

Five wind farm site visits were undertaken in November 2024 (Figure 3), these included three wind farms in the North-east of Scotland and two wind farms in the South-west of Scotland. These sites were chosen to cover a broad geographic distribution, a range of ages (different amounts of time since construction), and variation in peat depth. Visiting these sites provided a greater understanding of what was happening as part of the wind farm construction process, alongside providing context as to how peatland management plans are implemented and the many possible variations which can occur due to the amount of peat extracted, weather conditions and the inherent habitat quality prior to wind farm construction. These site visits also provided ‘real world’ examples of management practices in use, including (a) borrow pit reinstatement (over varying time periods – currently under construction, recent construction (< 5 years), 5-10 years since reinstatement, 10+ years since reinstatement), and (b) the replacement of peat at the side of the constructed roads (as part of the landscaping process and/or to maintain peat levels across the habitat).

Stakeholder Engagement Methods

During the study stakeholders were engaged for the following reasons:

• To gain insights into current practices for reuse of peat excavated on wind farms in Scotland.
• To gather views on the strengths, weaknesses, applicability and environmental outcomes of different reuse methods.
• To gather suggestions for examples and sites which could provide learning about the two points above.
• To gain input into the development of recommendations for reuse of excavated peat.

Appendix B Stakeholder engagement

Summary stakeholder engagement approach

Methods of stakeholder engagement:

Several different types of stakeholder engagement were employed in the study to gain further insights into relevant issues, current and potential future peat reuse methods, related considerations and impacts and to help identify sites to visit, get sign-posted to relevant documentation and research resources, and to understand considerations which are being or could be taken into account when decisions about reuse of excavated peat are made. Table 10 provides a brief overview of methods.

Table 10. Overview of stakeholder engagement methods

Dates	Activities	Purpose
Oct-Dec 2025	Research interviews with stakeholders / technical specialists.	Supplement desk-research.
Nov 2025	Site visits to wind farms incorporating local / other stakeholder engagement.	Gain insights into reuse activities on site, local context, site characteristics and how decisions were made.
Dec 2025	Academic / technical specialist online workshop	Supplement desk research, sense-check and refine draft recommendations.

Approach to identifying and selecting stakeholders to engage:

The project sought engagement with a range of different types of stakeholders academics and experts, such as those with a track record of relevant publications (i.e. on topics linked to the use of peat on wind farms in Scotland); practitioners from the energy sector (e.g. Ecological Clark of Works (ECoW) / Ecology officers) with wind farm sites in Scotland and from the construction sector that have been involved in building wind farms in Scotland; Civil Servants (Forestry and Land Scotland, PEAG); and conservation organisations (IUCN UK Peatland Programme). A selection of stakeholders were invited to attend the academic workshop, as well as a series of one-to-one discussions.

This approach to stakeholder engagement enabled the facilitation of site visits along with group discussions.

We identified stakeholders via:

• Introduction / recommendations from the project steering group – a group of specialists from across relevant Scottish Government Agencies (see Section 8.1.7.3)
• Desk research / REA – to identify relevant academics
• ‘Snowballing’ – asking our contacts and contacts via the steering group or other interviewees to recommend relevant technical experts or industry contacts who could provide access or insights about wind farm sites.
• We have sought a diversity of sites, with reasonable access – but to include a site further North if possible due to variation in vegetation colonisation rates for reuse on site.

When selecting wind farm sites to visit we aimed to achieve a diverse range of sites with reasonable access where we would be able to observe a range of different types and ages of reuse of excavated peat. We chose to include sites in different locations, including some further North due to variation in vegetation colonisation rates which we were advised in earlier stakeholder interviews could likely influence the outcome / progression of reuse methods. We contacted several wind farmer developers / operators – some via introduction and some via publically available contact details and also landowners such as Forestry and Land Scotland. The final selection of sites for visit was based on who was willing to host a visit and practical feasibility in the project timescale and available resources (see Section 9.4). During the visits our hosts often shared wider insights about considerations for reuse of peat and examples from other sites which had worked well or less well – these insights are included in the summary findings here.

When selecting stakeholders to interview we tried to ensure a diverse range of perspectives, but we did not set out to achieve a rigorous sampling approach – we had to take a more pragmatic approach to gather insights from willing participants. The snow-balling approach was valuable in helping us identify people to speak to with relevant scientific and technical knowledge and who could provide insights into what had happened on specific sites. We made a deliberate effort to speak to some stakeholders from outside industry organisations, including academics, non-profit organisations and contractors/technical consultants to achieve some balance in our research. A full list of interviews is in Section 8.1.7.1.

Stakeholder workshop

We held an online workshop for academics and technical specialists on 16^th December 2025 from 14:00 to 16:30. In total, 23 people attended (in addition to the Ricardo project team) including academic researchers, non-profit organisations, government agencies, energy company peatland specialists, see Section 8.1.7.2 for the list of attendees.

Workshop aims and objectives:

• Gather insights from previous research and ongoing studies which may not yet be published, to fill research gaps.
• Get insights into challenges / complexities which may need to be taken into account as we develop recommendations e.g. considerations for applying research results to different contexts / climates.
• Discuss, test and refine initial ideas for a hierarchy of excavated peat reuse (or similar simple structured approach which could help guide decisions on peat reuse, depending on what has come from our earlier research.

Whilst the focus of the workshop was to engage academic researchers and technical experts, we also had attendees from industry who were technical specialists with relevant insights to share about their experiences with peat reuse in practice and the day-to-day challenges associated with planning, implementation and evaluation of peat reuse.

Workshop agenda:

Table 11. Workshop agenda

Time	Session
14:00	Introduction: project framing, context and scope; participant introductions.
14:20	Project literature review overview & stakeholder feedback
14:55	Examples of current practices drawn from sites visits / stakeholder interviews: comments, questions, sharing other examples.
15:10	Stakeholder discussion / feedback
15:30	Present initial recommendations / peatland reuse hierarchy
15:40	Stakeholder feedback on recommendations / hierarchy
16:10	Final Polls: Feedback on options for recommendations
16:20	WRAP up and next steps

Findings from the workshop are incorporated into the stakeholder research results below (Section 8.1.6) and results of polls in Figure 8.

Figure 8: Results of word cloud (a) and other polls (b and c) undertaken during stakeholder workshop

a)

b)

c)

 

Method of analysis of stakeholder engagement findings:

Recording: Interviews	Transcripts and detailed notes of each stakeholder interview were recorded during the interviews and edited afterwards as needed to create an accurate record.
Recording: Site visits	During site visits photos and notes were taken relating to the site-specific context, practices and decisions. General learning was also noted, where for example the site host had experience across other sites or reuse practices.
Recording: Workshop	Transcripts and detailed notes were recorded during the workshop, as well as the results of polls and participation in interactive aspects of the workshop.
Analysis	Our project team systematically reviewed notes recorded from each element of the stakeholder engagement to identify comments related to the questions: Current reuse practices Potential future reuse practices Insights about environmental outcomes from peat reuse Other considerations Evidence gaps Priorities and recommendations.

Key findings from stakeholder engagement

Current peat reuse practices

During the workshop and stakeholder interviews a variety of practices were explained, along with associated issues, challenges and likely environmental outcomes or state of knowledge about the outcomes. The approaches are summarised in Table

Table 12. Current peat reuse practices

Current practice	Detail, benefits and issues
Borrow pit reinstatement, revegetation and habitat creation.	During site visits and interviews many examples of peat being put into disused borrow pits were shared. Common practices include: Reinstatement / infill with the layer of peat which was previously on top of the borrow pit – often only part filled and then landscaped on one side to create gentler slope. Depth of infill varies. Additional infill with peat excavated from elsewhere on site, sometimes designed with water outflow to mimic natural water flow. Creating structured cells within borrow pits to maintain structure / control water flows with the aim of keeping peat wet / creating functioning peat bog or similar habitat. Other practice examples included: Allowing peatland heath type vegetation to develop in borrow pits without infilling any excavated peat (presumably when there was not excess peat). Piping out peaty slurry from turbine bases into borrow pits. Issues flagged included: Water flows after infill – best practice is unclear, and design is unclear. Peat depth – variable depths were filled, unclear whether all comply with current guidance[15]. Expense of constructing cells. Insights shared about environmental outcomes: Some examples seemed to have peatland vegetation indicator species and high-water tables Often on slopes in landscaped borrow pits drier habitats develop. Mixed success in maintaining / re-establishing vegetation cover meaning peat is sometimes left bare. More pronounce in northerly locations with slower vegetation colonisation.
Roadside verge reinstatement or revegetation.	A very common practice – excavated peat is stored alongside the road after construction, typically until after cables have also been laid, and then peat is reinstated. Sometimes: Efforts are made to maintain structure and place turves on top for later reuse. Wider verges are created / landscaped to hold more excavated peat from elsewhere on site. Reseed to improve vegetation cover – although not common practice. Issues flagged included: Likelihood of peat drying out whilst store on roadside. Significant risk of mixing soils and changing nutrient balance. Significant risk of wind / water erosion during storage. Convenience prioritised over effectiveness Insights shared about environmental outcomes: Mostly viewed as something unlikely to return to functioning peat bog due to peat storage, handling, contamination and proximity to road which will affect drainage. Carbon may be lost during storage. Revegetation, including wet heath type vegetation, was feasible or they knew of examples. When vegetated can be beneficial to prevent silt / clay fines washing off into the wider landscape.
Infill historical peat cuttings	Not common but is used sometimes where peat cuttings are on site. Limited information was provided – unclear whether turves were placed on top or natural revegetation happened. Example of storage in peat cuttings before use in incorporation into a restoration project was also cited. Issues flagged included: Only possible where peat cuttings exist – declining availability. Insights into environmental outcomes: Wet heath / acid grassland appeared to have developed on one site – although no vegetation survey data was available to confirm this. Hydrological functioning / GHG emissions unclear – not data / other insights shared. Reuse of peat where it had historically been located
Incorporate excavated peat into peatland restoration projects (pilot projects)	During two site visits and in other conversations examples of pilot projects to incorporate excavated peat into peatland restoration. Methods included: Adding a layer of peat under existing turves / filling landscape furrows on former forested site. Infilling bare sections of peat between hags, on degraded / eroded natural peatland areas. Issues flagged included: This is an experimental practice and not routinely permitted. Access to suitable sites: access for earth works vehicles is difficult, making it hard to do larger areas away from tracks, without creating new access tracks. Soil mixing is hard to avoid which can change nutrient balance in the peat and influence end result. Designs aim to manage water to support peat formation whilst also ensuring safety / stability – different views were shared about how this should be done and appropriateness of approaches on site. Insights shared about environmental outcomes: Success of vegetation recovery/formation of active peat bog appears mixed so far, although long term observations and measurements are not available to enable evaluation. GHG emissions fluxes are unclear – no monitoring data available.
Drainage related practices	Multiple stakeholders shared views and experiences on the role of drainage on site currently and typical practices. Current practices vary: Infilling: some drainage ditches created during construction are infilled, and some aren’t. Those which are, are filled with arisings from the ditch creation, which would have been stored alongside for the duration of construction, mostly likely with limited management e.g. wetting. Construction methods: ‘rock-filling’ above ground level in road construction to maintain water flows (floating road example)[16]; Angled flumes and other practices to separate silty or polluted drainage water to avoid wider pollution / silt spreading. Issues flagged included: Possible excessive / unnecessary drainage on some sites, having a detrimental effect on peatland habitats on site. The importance of maintaining some ditches / drainage to ensure site stability and safety. Insights shared about environmental outcomes: Stakeholders felt that excessive drainage may hinder chances of successful recovery / recreation of peatland habitat re Drainage important to maintain integrity of construction process – do not want to risk a peat slide Scope for some of the temporary works drains to be infilled (usually with the arisings from the ditch itself) – however this is often not done (and doesn’t provide scope for vast quantities of peat reuse).
Peat handling & storage practices	Typical practice examples: Roadside piles – various heights, various levels of attention to maintaining structure and wetness, varied timescales. Efforts to minimise handling / transport often cited. Insights shared about environmental outcomes: Carbon lost when peat oxidises – often results when it dries out or is subject to erosion. Carbon emissions from fuel use for transport around site (or off-site if that were to happen).
Off-site reuse of peat	No stakeholders cited any examples of peat being reused off-site – many had years of experience in the sector and had never known this to happen.

Other feedback provided by stakeholders on current practices included:

• Variable ‘aims’ of reuse currently – ranging from developers who are trying to create functioning peatland on previously degraded land through to examples where people suggested there was no clear intention beyond finding a place to put the excess peat.
• Compliance with guidance: multiple stakeholders shared a view / example that guidance is not always followed particularly in relation to peat infill depths and handling practices – reasons were unclear, although separately a skills gap was mentioned.
• Quality of PMPs: varied – some followed fairly standard practice without consideration of the uniqueness of the site, whilst some were more nuanced / based on more detailed analysis of possibilities and potential outcomes
• Enforcement / monitoring of PMPs: enforcement / monitoring during constructure can be inconsistent – sometimes very good collaboration and active consideration of effective approaches to achieve good environmental outcomes and sometimes poor / ineffective. Monitoring after construction and commissioning is not common practice, except were linked to habitat management plans which have a formal requirement for monitoring over the life of the site.
• Influence of contracting process and responsibilities: separate contracts for different parts of the windfarm design and construction are commonly let which can make it difficult to develop and maintain a coherent plan for peat management through from planning permission through to final build and ongoing management. The wind turbine specification can also dictate excavation e.g. to achieve desired gradient for installation, but with more site surveys and consideration between developer, turbine supplier and site works contractor there may be potential to develop techniques which require less excavation.
• Important of site selection / micro-siting: the flexibility to move turbines, based on more detailed site surveys of peat is important to reduce peat excavation.
• Reuse of peat is well policed – must be in line with SEPA Reuse Guidance and therefore industry stakeholders follow this approach without feeling able to vary from this.

Potential future reuse practices

Practice	Details, benefits and issues
Deliberately targeting specific end habitat e.g. in borrow pits	Stakeholders suggested that it may be feasible to design reuse more intentionally with target end-habitat in mind e.g. designing the borrow-pit structure and planning peat excavation and handling specifically with the aim of targeting a valuable habitat – peat bog recreation if feasible or if not, another locally suitable and ideally wet habitat type. There was uncertainty about how to ensure success and what outcome was feasible on a site-by-site basis given the variability between sites in terms of prior land condition, surrounding context and land scape and land ‘capability’ for habitats.
Further use in restoration	Some stakeholders felt the incorporation of excavated peat into restoration projects had potential to achieve good environmental outcomes – examples highlighted were infill in degraded and eroded peatlands including hag infill, incorporation in former forested / forest bog landscapes – various methods being piloted. Some apparent success of vegetation recovery on pilot examples was flagged, but stakeholders acknowledged that the environmental outcome were unclear. Some stakeholder flagged potential concerns about the effectiveness of this approach due to: Difficulty establishing vegetation on slopes Potential challenges with water flows, depending on locations and hydrology. Impact of damage during the restoration process and skills needed in planning, preparation and handling to achieve a good outcome. Site stability / drainage – general agreement on its importance but different views on how to achieve / balance with other priorities leading to some concern about how to approach more experimental methods.
Infill of drainage ditches (where safety/stability allows)	Stakeholders flagged that, whilst it is important for site safety and stability to ensure suitable drainage is maintained, there could be opportunities to infil more drainage ditches or increase overall wetness on site to benefit existing peatland habitats on site or increase the likelihood of successful peatland habitat forming where peat reuse has aimed for this outcome.
Off-site uses	We asked whether uses such as agriculture/horticulture whiskey industry use would be feasible or environmentally beneficial in any circumstance or whether they knew of any other examples. No stakeholders felt that off-site use was a good idea due to: Costs likely loss of peat structure / liquification during transport environmental impacts of transport likelihood that carbon would be lost from peat in the new use – lack of control over this.

Insights about environmental outcomes from peat reuse

Examples and comments on positive environmental outcomes:

• Peat / vegetation recovery in restoration / hag infill – appears successful (in short-term) on flatter ground.
• Softer trackside verges – vegetation and less slope – can prevent silt migrating into bogs.
• Typical vegetation recovery: acid grassland mix initially, then (5-10yrs later) heathers / heath, and then hopefully wetter ones will progress to bog.

Examples and comments on negative environmental outcomes:

• Most peat reused on wind farms turns into non-peatland habitat – it doesn’t function as peatland because hydrological conductivity is lost. At best going to form an upland wet heath, more likely to be an acid grassland.
• If non-functioning peatland carbon will not be saved within the system Need to keep the carbon gaining and building within the system.
• With poor water management silt is migrating into wet bogs.
• Contamination of nutrient poor peatbog with mineral sources changes nutrient balance and therefore makes peatbog hard to achieve in reuse/restoration – flushed peat or fen more likely. Several stakeholders flagged that it can be challenging to prevent mineral contamination – storage and handling care is needed, and isn’t always feasible in practice.

Other comments on environmental outcomes:

• Potential measurement approaches:
• GI stage, peat probing / wetness, catchment mapping, qualitative sample (no one does this despite guidance), Van Post Scale (peat character).
• Dip wells – across sites.
• Water index via satellite imagery linked to Sentinal programme.
• Pressure loggers – data recording for three months.
• Options for assessing carbon; current government calculator, in house planning tools; revised carbon calculated – potential for different assumptions about loss of carbon on excavated peat.
• Important to balance carbon / biodiversity outcomes. Some stakeholders flagged this in general and also one highlighted the challenge of balancing this in the context of deciding whether to rewet peat during storage – if abstraction from river is required this could have negative consequences for river habitat.
• Several flagged nervousness about assuming reused and restored peat delivers the same environmental outcomes as natural peatlands.

Other considerations for excavated peat reuse

Drainage installation, maintenance and infill: stakeholders agreed that ensuring the right amount of drainage during construction and afterwards is important, but did not all agree on how well this is currently being achieved and whether it is possible provide clearer guidance on this.

Peat handling & storage: many stakeholders flagged the need to minimise movement and handling of peat, aim to keep peat local, minimise handling / travel distance. Use of large diggers and trucks makes this hard. Issues included:

• Need to keep the peat moist: actively or passively
• Need to maintain layers / structure and avoid contamination with mineral soils / aggregate as this will change the nutrient profile and functional structure of the peat.
• Peat can liquify in trucks if handled.
• Cost for moving peat
• Some flagged that temporary storage in ‘groins’ between road junctions is often preferred as there is more space to work there, whilst other advocated designated storage areas. What is practical will vary site to site.

‘Land-made-available’ limitation: land envelope can restrict end destination of any peat reuse ‘on site’ – instances where sensible areas for ‘peat reuse’ are outside the envelope.

Site data availability: planning the peat re-use in advance would be good but often don’t get chance to plan until actually on site and work starts – trees often obscure lidar data.

Excavation timing: contractors don’t get much choice/penalties for delays – timing will influence ability to keep peat wet, keep structure etc.

Evidence gaps

Stakeholders flagged the following issues and gaps in evidence:

• Limited monitoring of implementation and outcomes of Peatland Management Plans (PMPs). Monitoring isn’t required for PMPs in the same way as for Habitat Management Plans (which are monitored for the life of the wind farm), and therefore limited data is available on prior land condition, peat reuse/management methods, and environmental outcomes.
• Approach and quality of assessments and monitoring could be better. Current over reliance on the presence or absence of specific vegetation as an indicator was highlighted – finding a species at a specific location in a large site doesn’t represent the entire site. Better quality peatland condition assessments are needed, ideally landscape based incorporating species, hydrology and other factors rather than quadrat based. This would provide better data for planning reuse / management and a better baseline for impact monitoring, particularly important as construction is often on degraded peat.
• Lack of longitudinal studies into environmental outcomes of peat reuse/management approaches. People cited specific gaps such as study of behaviour and environmental outcomes of peat drying at the side of the road after reinstatement; impacts of storage techniques such as surface roughing to help water infiltration vs allowing crust to form; GHG emissions following disturbance and reinstatement.
• General gap in terms of the understanding of peatland and peat behaviour in the context of wind farm construction. This includes peatland hydrology and how this is affected by disruption, how peat behaves in storage, the impact of movement on peat quality and potential for reestablishment in new destination
• Evidence of the validity of measures such as water table and indicator species as indictors of GHG emissions / ‘functioning peat bog’ for reinstated / restored peatlands. Stakeholders flagged there is no research on peatland excavation and then reuse, hence need to establish the relationship with vegetation, hydrology.
• Limited literature on remote sensing for wind farm monitoring.
• Lack of clear guidance on some aspects of engineering and site management e.g. balancing drainage and wetness, storage practices.
• Lack of research to show whether implementation of best practice is feasible. NPF4 Policy 5 states that ideally carbon rich soils are actively sequestering carbon, and this should be the aim of the PMP. There is a need for research to show if this is possible – this relates to points above about behaviour of peat after disturbance / validity of indicators.

Priorities and recommendations

In general stakeholders were reluctant to give detailed feedback on which methods of peat reuse on site should be a priority because of variability of site circumstances (e.g. land capability, condition) and the lack of concrete research to provide evidence of the environment outcomes which could be anticipated.

Some key comments and points on priorities were:

• Revegetation and minimising bare peat is key to avoid negative cycle of drying and/or erosion: to help success it is important to have follow up surveys and action if issues are identified.
• Need to minimise extraction of peat.
• Advice must allow for flexibility and be nuanced due to the diversity of peatlands.
• Suggested hierarchy:
• Avoid;
• Reinstate in location contiguous to other peatland where carbon can be retained and retain hydrology and long-term species composition will be at least consistent with species within the species disturbed.
• Re-use off site to the same effect.
• Alternative suggestion: two different hierarchies, one with the aim of functioning peatland, and one for the aim of using peat in a way that would result it being used for another purpose e.g. wet heath, dry heath.
• Essential component is maintaining connectivity of the re-use areas with the hydrology and its immediate area, but also looking further at the wider hydrological unit. This also includes connectivity with the peatland restoration areas that will be undertaken on the site.
• Guidance documents can be perfect, however, on the ground can be challenging e.g. to ensure hydrological connectivity – potential need for incentive to go for the best outcome and need to involve different parties to achieve this.

List of stakeholder discussion interviews and workshop attendees

Interviewees

Susan Nicol	Forestry and Land Scotland
Andy Gillan	RJ Mcleod
Mark Mulqueeny	SSE
Derek Healy	Duncan Mackay and Sons
James Allison	Scottish Power
Emma Taylor	SEPA
Roxane Anderson	University of Highlands and Islands
Gill Steel	Ironside Farrar
Siue Allen	Ironside Farrar
Malcolm Crosby	Forestry and Land Scotland
Richard Clarke	Forestry and Land Scotland
Sue White	Shetland Community Trust
David McGinty	SSE Renewables

Workshop attendees

Name	Organisation	Role
Andy Mills	OWC Ltd	Geomorphologist writing many PMP’s
Andy Gillan	RJ McLeod Contractors	Construction projects on peatlands
Irene Tierney	IMTECO Ltd	Ecologist writing many PMP’s
Emma Hinchliffe	IUCN UK Peatland Programme	Director
Cerian Baldwin	PeatlandACTION	Technical director involved in development, Scottish Peatland Standard and reviewing PMPs and EIAs in relation to peat
Alan Cundill	SEPA	Senior Specialist Scientist interested in reuse/management of peat
Claire Campbell	SEPA	Senior Specialist Scientist and reviewing PMP’s
Jessica Fìor-Berry	IUCN UK Peatland Programme	Peatland Programme policy lead
Karen Rentoul	NatureScot	Policy advice manager for uplands and also peatlands
Rachel Short	ScottishPower Renewables	Senior ecology manager responsible for design, construction and operation of wind farms, many on peatlands
Fiona Donaldson	SEPA	Waste policy unit interested in management of excavated peat
Grace Gubbins	NatureScot	Involved in the development of the biodiversity metric for the planning system, also supporting peatland expert advisory group
Roxane Andersen	University of Highlands and Islands	Peatland scientist, also sit on peatland expert advisory group
Chris Marshall	SLR Consulting	Peatland lead dealing with many PMP’s
Susan Nicol	Forestry and Land Scotland	Land managers leasing land for wind farms
Kirsten Lees	University of Derby	Peatland restoration with focus on carbon
Ainoa Pravia	Forest Research	Ecologist (for peatlands)
Iain Detrey	EA	Peatland adviser (for England)
Nicholle Bell	University of Edinburgh	Peatland restoration, and alternative reuse options
Kerry Dinsmore	SG	Principal science advisor on peatlands, also on steering committee

 

Project steering group

Ben Dipper (Scottish Government)

Kerry Dinsmore (Scottish Government)

Patricia Bruneau (Nature Scot)

Scottish Government policy team representatives

Appendix C Wind Farm Site Research (site visits & desk research)

Wind farm planning document review

This section reviews the desk-based research describing existing wind farms management plans including data on numbers of wind farms across Scotland on peat soils.

Wind farm site visit summary

This section combines the results of the desk-based research describing existing wind farm management plans alongside the information gathered during the site visits. We aimed to visit a diverse range of sites with reasonable access where we would be able to observe a range of different types and ages of reuse of excavated peat. We chose to include sites in different locations, the north-east and south-west of Scotland. In both areas we visited a newly constructed wind farm, alongside older wind farms within the same locality. This provided examples with different vegetation colonisation rates which could influence the success of reuse methods. We contacted several wind farmer developers / operators, the final selection of sites for visit was based on who was willing to host a visit and practical feasibility in the project timescale and available resources.

Desk-based findings

We reviewed the planning information prior to site visits. This included information on when the work was completed / site commissioned to generate energy, the number of turbines that had been built (both initially and in phased extensions), land ownership and whether other stakeholder were involved in the process (e.g. wildlife rangers based on site, ECoW’s).

Sample site selection

Site selection was undertaken taking into account key variables to ensure that a representative sample of wind farms across Scotland was obtained. Primarily, this included considering a range of development site sizes and locations across Scotland, while ensuring that wind farms were both operational and included relevant Peat Management Plans (PMPs). To note, the number of wind turbines was used as a proxy for development size, while the requirement for developments to have PMPs significantly reduced availability of case studies (even though this is an NPF4 requirement).

Peatland management plans

The key limitations in the approach concerned the accuracy of the data held within the PMPs, for which accessing documents with the requisite information (peat depths and volumes) was the first challenge. In those PMPs that were available, the peat volumes were based on peat survey depths, which are extrapolated across sites via peat probe information, meaning that there is a degree of uncertainty between distinct probe points. There is therefore a high degree of mathematical assumption based on converting peat depth extrapolations to volumes via combining this data with site stripping boundaries. Utilising survey information also assumes competence of all surveyors, despite peat surveys (and peat identification more generally) being a highly specialist skill that geo-environmentalists, geotechnical specialists and even soil scientists would not necessarily have experience of. In addition, peat volumes included in PMPs can change during the construction phase, such as where design is updated, or due to poor implementation of PMP measures. This means that volumes at project inception are often unlikely to be the same once wind farms are conducted, given the dynamic nature of the construction phase and typically iterative design approaches.

Overview of key finding from site visits

Key highlights are included in the main section 3.5.2, 3.5.3 and 3.5.4. A number of borrow pits were visited at each of the sites – these varied in effectivity, levels of monitoring and time since reinstatement. Landscaping examples where peat had been put down along the roadside were clearly visible in the newly constructed wind farms, in the older wind farms this was less obvious, in some cases the peat had become part of the surrounding peatland, however the likelihood was that in some areas it had been lost to the wider environment through erosion. Novel restoration reuse was seen, this was experimental and not common practice. No peat was taken off-site for reuse elsewhere.

Limitations of site visits

Although we were very grateful to the stakeholders for taking the time to show us the wind farms and distil their knowledge of the process, it was clear that this view was only able to provide a snapshot in time analysis of what had occurred at that site. Also depending on time from commissioning, some key details related to the reuse of peat were lost (e.g. exact volumes of peat used within infill of peat excavations, how borrow pit reinstatements were originally designed). Thus, it is harder to identify best practice and what has worked and what hasn’t if the methodology is unreported. The site visits could have been impacted by the weather conditions on the day (e.g. low cloud and drizzle for the final site visit), this made note taking and photographing examples harder and some of the finer details may not be visible in the photographs.

 

How to cite this publication:

Crotty, F., Dowson, F., Schofield, K., Barker, M., Ginns, B., David, T., Herold, L. (2025) ‘Reuse of excavated peat on wind farm development sites’, ClimateXChange. DOI: http://dx.doi.org/10.7488/era/6333

© The University of Edinburgh, 2025
Prepared by Ricardo on behalf of ClimateXChange, The University of Edinburgh. All rights reserved.

While every effort is made to ensure the information in this report is accurate as at the date of the report, no legal responsibility is accepted for any errors, omissions or misleading statements. The views expressed represent those of the author(s), and do not necessarily represent those of the host institutions or funders.

This work was supported by the Rural and Environment Science and Analytical Services Division of the Scottish Government (CoE – CXC).

ClimateXChange

Edinburgh Climate Change Institute

High School Yards

Edinburgh EH1 1LZ

+44 (0) 131 651 4783

info@climatexchange.org.uk

www.climatexchange.org.uk

1. 
   

   https://www.wwt.org.uk/discover-wetlands/wetlands/peat-bogs ↑

   
   
2. 
   

   https://www.nature.scot/sites/default/files/2023-02/Guidance-Peatland-Action-Peatland-Condition-Assessment-Guide-A1916874.pdf ↑

   
   
3. 
   

   John Muir Trust – Scotland’s peatland policy update. ↑

   
   
4. 
   

   https://www.gov.scot/publications/carbon-calculator-for-wind-farms-on-scottish-peatlands-factsheet/ ↑

   
   
5. 
   

   https://www.legislation.gov.uk/ssi/2011/228/contents ↑

   
   
6. 
   

   https://www.sepa.org.uk/media/287064/wst-g-052-developments-on-peat-and-off-site-uses-of-waste-peat.pdf ↑

   
   
7. 
   

   Scottish Renewables, Scottish Environment Protection Agency. 2012. Guidance on the Assessment of Peat Volumes, Reuse of Excavated Peat and the Minimisation of Waste ↑

   
   
8. 
   

   https://www.heraldscotland.com/news/18270734.14m-trees-cut-scotland-make-way-wind-farms ↑

   
   
9. 
   

   https://www.sepa.org.uk/media/287064/wst-g-052-developments-on-peat-and-off-site-uses-of-waste-peat.pdf ↑

   
   
10. 
    

    https://www.nature.scot/climate-change/nature-based-solutions/nature-based-solutions-practice/peatland-action/peatland-action-how-do-i-restore-and-manage-my-peatland-0 ↑

    
    
11. 
    

    Micro-siting is where small adjustments to the wind farm lay out are made to avoid / minimise damage to peat (or other sensitive environments) on site. ↑

    
    
12. 
    

    Renewable Energy Planning Database: quarterly extract – GOV.UK ↑

    
    
13. 
    

    Renewable Energy Planning Database: quarterly extract – GOV.UK ↑

    
    
14. 
    

    https://www.data.gov.uk/dataset/ed1922b7-1136-442c-af4d-a36ebad8839f/carbon-and-peatland-2016-map-wind-farm-spatial-framework ↑

    
    
15. 
    

    It was unclear whether stakeholder was referring to current or previous guidance. ↑

    
    
16. 
    

    A method described to us where rocks are piled, rather than smaller aggregate to create a more porous substrate allowing for greater water flow. ↑