Scotland’s Climate Change Plan includes a policy commitment to reduce emissions from the use and storage of manure and slurry.

Agriculture and associated land use account for 24% of greenhouse gas (GHG) emissions in Scotland, with methane the most significant proportion of this at 44%. Methane comes from manure and enteric fermentation. The management of manures is therefore a critical element in mitigating the sector’s GHG emissions.

This study examines the feasibility of developing manure exchanges (slurries and farmyard manures) to reduce these emissions. 

 

Main findings  
  • The arisings of manure in Scotland indicate a total available nitrogen supply of 14,700 tonnes per annum from manure, compared with a total utilisation of applied nitrogen of approximately 152,000 tonnes.
  • A significant proportion of manures could potentially be part of a manure exchange, with just 6% of manure arisings currently reported as being exported from source.
  • The potential abatement of GHG emissions by offsetting manufactured nitrogen through the substitution of organic manure is limited. Under the most favourable scenario modelled, the potential saving is equivalent to just 0.68% of annual agricultural emissions.
  • We found three broad examples of schemes which support the movement of manures and would be relevant within the Scottish context: muck-for-straw, manure exports and movement of livestock.
  • Requirements for nitrogen are greater in all major regions of Scotland than can be supplied by manure sources.
  • Compared with other European countries, Scotland does not have a significant oversupply of livestock manures at a regional level.
  • There are environmental challenges associated with manure and slurry production and storage at an enterprise level, particularly for water quality. The potential for local surpluses has therefore been the focus of this study.
  • Surpluses of manure can lead to localised environmental impacts if they are not managed correctly. The factors influencing the success of manure exchanges rely on the recognition of costs and barriers and on investment in establishing agreements.
  • A strategic, regional or national scale exchange model is unlikely to be cost effective for GHG gas abatement. However, there is some potential to support exchanges of manure through improved local distribution (i.e. within a holding or with close neighbours).
  • The most useful measures are those that focus on the utilisation of manure nutrient value and that form part of an integrated policy alongside other drivers such as water quality (Water Framework Directive), Nitrate Vulnerable Zones, air quality and productivity.

 

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Scotland’s Climate Change Plan makes a policy commitment to reduce greenhouse gas (GHG) emissions from nitrogen fertiliser through improved understanding, efficient application and better soil condition.

This report considers the potential for nitrogen and urease inhibitors to support emission reductions in Scotland, considering Scottish circumstances and conditions, such as soils, crops, rainfall and temperature.

These inhibitors are particularly important for those who are modelling both GHG emissions and air quality. However, while some studies provide consistent messages concerning the evidence of their effectiveness and their impacts on the wider environment, others are contradictory.

Main findings

The evidence indicates that:

  • There is generally a positive potential impact of inhibitors on GHG and ammonia emissions under Scottish conditions, especially for nitrification inhibitors.
  • There are no significant concerns over the efficacy of inhibitors in Scotland. Low uptake relates to the niche market; inhibitors are primarily supplied for agronomic benefit with relatively marginal economic gains in most circumstances.
  • While the efficacy of inhibitors has been confirmed by the review, there remain uncertainties over the magnitude of emissions reductions. There are also questions relating to the environmental risk, trade-offs with potential emission/pollution switching, industry knowledge and practical implementation.
  • The persistence of the effects for both nitrification and urease inhibitors are likely to be impacted by a warmer climate, although any impact is likely to be minimal. Emissions from unabated fertilisers are expected to increase as climate change progresses. Under these conditions, the role of inhibitors as a tool in mitigating emissions becomes increasingly important.

The evidence for environmental risks includes:

  • There is little evidence exploring the impacts of N inhibitors on soil health and on impacts to non-target and nitrifying organisms.
  • Use of nitrification inhibitors can lead to increases in ammonia emissions. However, alongside this, there are benefits for other environmental indicators (particularly GHG emissions and nitrate leaching). The potential increase in ammonia emissions can be mitigated by use of nitrification and urease inhibitors together.
  • Some research highlights the risk of DCD (dicyandiamide – a nitrification inhibitor) leaching into surface and ground waters. This can have adverse effects on aquatic systems.
  • There are concerns regarding animal consumption (directly or via traces found on grass/hay) as DCD has been found in dairy products in New Zealand. This led to DCD being banned in New Zealand.
  • Increased risk of ammonia release from use of nitrification inhibitors will have adverse impacts on ecosystem biodiversity through deposition and increased N loading to sensitive sites.

The main practical/commercial considerations are:

  • Nitrification and urease inhibitors are not widely used due to poor cost effectiveness under conventional economic analysis at farm gate (i.e. not considering externalities of environmental or societal costs).
  • In the agriculture industry, there remains significant misunderstanding over the roles and practical application of inhibited fertilisers.
  • Investment in nitrification inhibitors will not be driven by market pull. Stakeholders feel N inhibitors are not currently attractive prospects for increased investment.
  • Urease inhibitors are more commercially viable (compared with nitrification inhibitors) and have potential economic benefits due to the potentially high emissions of ammonia losing significant N content. Interest and awareness of urease inhibitors is greater.
  • Price sensitivity: farmers in the UK are very sensitive to fertiliser price and will seek the most cost-effective source of N. A perception of little or no economic value in inhibited fertilisers will discourage adoption.
Commercial forestry has in recent decades become highly dependent on a small number of conifer species, particularly Sitka spruce. Adaptation and resilience of productive forestry is affected by risks from climate change and a number of high impact tree pests and diseases. These risks have prompted policy, practical and industrial concerns about over-reliance on a small number of tree species.

There is renewed interest in alternative conifer species including western red cedar, firs, western hemlock and Douglas fir, all of which can produce valuable timber if grown competently on well-selected sites. Most research about diversification focuses on the biological and economic aspects of these changes. However, change in practice will only come if the people who produce, manage, harvest and buy the trees are willing and able to work in different ways.

This report considers the implications of a shift in forest management through the lens of species diversity. 

Key findings include:
  • Species choice is a social as well as an economic and technical choice, because different people involved in land use have different objectives and preferences.
  • Tree nursery producers, forest managers and sawmill businesses all influence species choice through supply and demand relations, as well as through preferences and shared values
  • Stakeholders experience risk in different ways.
    • Nursery businesses are bearing the most tangible component of risk at the outset, and paying the cost of low confidence in policy direction.
    • Sawmills are adapting to a wide range of species, and more than they are usually credited with.
    • The private investment forestry sector is the least interested in change, because most of their clients are driven by the search for high returns on their investments. 
    • Public forest managers are committed to diversification but are forced to take an experimental approach because of the scarcity of experience and site-specific information on cultivating alternative species.
  • Both private and public forest managers identify deer populations, and their preference for browsing species other than spruce, as a particular constraint to commercial diversification.

The Scottish Government has a commitment to restore Scotland’s peatlands. An element of this is to phase out the use of peat in horticulture. This Rapid Evidence Assessment looks at the current state of knowledge on the role of peat in UK growing media, and the potential for alternative growing media constituents.

There are significant gaps in Scotland-specific data. Our review of published literature (both grey and academic) has therefore been supplemented by information from industry experts.

Main findings
  • Peat extraction in Scotland occurs mainly on lowland raised bogs in the south and east of the country. Estimation of extraction volumes is hampered by information gaps, but is of the order of 0.5 million m3 per year. This represents perhaps 60% of the estimated 0.8 million m3 of UK production.
  • Estimated carbon emissions arising from extraction in Scotland are of the order of 100k t CO2e per year, which could be avoided if all extraction ceased. However, alternative media also emit carbon so the net saving would be lower, at around 50k t CO2e per year, if they were used instead.
  • Scotland-level estimates of peat consumption are not available, but UK-level estimates show that overall demand for horticultural growing media is approximately 3.8million m3, of which 2.1million m3 (55%) are peat-based. The shortfall relative to domestic production is met by imports, principally from the Republic of Ireland.
  • Within overall demand for horticultural growing media, professional users (e.g. landscape gardeners, commercial growers) account for about 1.1 million m3, of which 65% is peat-based, whilst amateur users (i.e. households) account for about 2.7 million m3, of which 51% is peat-based.
  • A variety of alternatives to peat are available, including coir, pine bark, wood fibre and composted organic waste. Most need to be mixed with other ingredients and are more expensive and not as readily available as peat. For example, wood fibre is also in demand for renewable energy.
  • Peat-free alternatives have gained market share since the 1990s, but peat-based media remain commonplace. This reflects advantages offered by peat in terms of availability, price and consistency which are hard to replicate with alternatives and hence have to be traded-off against other criteria, such as environmental impact. The weight attached to different criteria will vary across different users, but those not already switched to alternatives may be harder to convert.

Snow cover is a key aspect of what defines the character of the Cairngorms National Park (CNP). It underpins the ecology, hydrology and economy, which are all dependent on how much snow falls, and where and how long it stays.

In this summary assessment we compared historic temperature and precipitation data (1918-2018) with observed snow cover days (1969-2005) to identify how temperature affects snow days. We then modelled future snow cover days using the best available data generated by the UK Met Office to identify some possible trends for the Cairngorms National Park. 

Modelling snow cover based on climate projections is challenging, and we currently only have daily climate data projections for the high emissions scenario. However, our initial results show a reduction in snow cover as the observed warming trend continues and accelerates. Successful global efforts to reduce emissions may moderate this impact, whilst even higher emissions rates (e.g. due to ecosystem carbon releases) may further increase impacts.

Key findings
  • There has been an overall decline in observed snow cover in the Cairngorms National Park (1969-2005). This trend conforms to those seen across other mountain areas and the Arctic and is in keeping with the observed global warming trend.
  • There is a clear observed decrease in the number of days of snow cover at all elevation levels over the 35 winters between 1969/70 and 2004/05, with higher elevations having a larger proportional decrease.
  • In the near-term, our estimates indicate the potential for a continuation of snow cover at the current range of variation, but with a substantial decline from the 2040s. These findings are in line with results from the UK Meteorological Office and Inter-governmental Panel on Climate Change (IPCC 2019).

The area of peatland restoration that can be delivered each year is limited by a number of factors, including physical accessibility. This short project used existing data on proxies of snow cover and degree of difficulty for access to estimate the proportion of time in an average year that restoration would not be possible.

  • Our results suggest that, nationally, during periods of between 2 to 100 days per year, conditions could make sites physically inaccessible to efforts to carry out peatland restoration. This will vary depending on the specific site location, and our model is able to provide such data for individual locations.
  • Peatland condition categories more likely to be located at higher altitude (e.g. eroded peatland) or further from access roads (e.g. heather- or grass-dominated modified bog) had higher average number of days that would be inaccessible than condition categories associated with better human access (e.g. peat extraction, cropland conversion, intensive grassland).
  • The values were mostly determined by the estimate for snow cover, with only a smaller proportion attributed to the additional time required to access a site.
  • This analysis is highly sensitive to the assumption that the Met Office days of ground frost are an appropriate proxy for the number of days a site would be inaccessible due to snow on the ground.  It does not take into account other restrictions to access.
Agriculture accounts for the second largest proportion of greenhouse gas emissions in Scotland, particularly through the use of fertilisers, livestock manures and other organic materials such digestate or compost. One approach that could help to reduce these emissions is the use of nitrogen accounting tools. In this report we compare available nitrogen accounting tools to assess their potential application focusing on Scottish agriculture.

 

With a focus on input-output models, we evaluate the strengths and weaknesses of different models, their practical potential for application to Scottish farm businesses, and their potential to support policy decisions.

 

Key Findings
  • Generally, there are common knowledge gaps across many of the tools assessed.  This includes a lack of detailed description for nitrogen parameters such as deposition, gaseous losses (particularly ammonia losses), fixation rates (based on legume type and coverage), content in feed, machinery use and wider. Gaps were also found in evidence for the use of novel technologies on farms, efficiency differences from livestock breeding programmes and how the nitrogen accounting tools link more widely, for example with sectors such as industry, transport, human consumption and waste.
  • We found that the tools available have been designed for specific (different) purposes that vary in spatial scale and which differ in complexity, both in how easy they are to use and in the details describing nitrogen pathways in agricultural systems.
  • At the national and regional scale from the identified tools, the model by Vogt and the UK Smart Inventory shows the greatest potential to be developed into a national level policy monitoring tool. On the other hand, Farmscoper and IMAGE would be suitable to explore alternative scenarios in the near and further future, respectively.
  • The tool evaluation process determined that, of the tools reviewed, PLANET, MANNER-NPK and potentially FarmAC are most suitable for Scottish application for calculating farm-level budgets at this time. However, the OverseerFM tool provides the most holistic coverage of farm level management practices influencing nitrogen inputs, transformations, storage and outputs from a farm.

Producing the meat we eat contributes to greenhouse gas emissions. 

A first step to lowering emissions is to understand how greenhouse gas emissions may vary between breeds. This report assessed the current state of confident knowledge for cattle.

Key findings:

  • No clear difference was found between breeds
  • Cattle have not been bred on the basis of their emissions – any differences are based on feed intake or production system
  • Those bred for high productivity may have lower methane emissions per kilogram of beef produced because they consume a smaller amount of feed
  • An animal that can digest its food more quickly will generate fewer emissions as there is less time for processing in the stomach
  • Breeds selected for higher production will have reduced greenhouse gas emissions, particularly when expressed relative to production

However, the evidence shows that selective breeding can be linked with problems of ill health, increased death rates and reduced fertility, and so overall reductions in greenhouse gas emissions will depend on minimising these risks – for example by having an appropriate breed for the environment or management system.

One way to reduce the carbon footprint of the food we produce is to use more efficient methods in agriculture, but we also need to gather information on what works best and how we are getting better.

 

This research was designed to develop a robust method for generating intensity data for greenhouse gas (GHG) emissions on Scottish farms. We wanted to be able to generate an estimate for individual farm businesses, and also scale up to a Scotland level, and to be able to repeat the process so that improved performance could be recorded. This work is focussed on beef production. 

 

We designed a framework that could begin to calculate the intensity of the emissions – that is, the amount of emissions per unit of production (for example, per kilo of beef). using data on GHG intensity from carbon footprinting tools.  We concluded that there is considerable potential for the framework to generate an estimate of emissions intensity, although more detailed information across a wider range of farms will improve its robustness.

 

The UK’s inventory of greenhouse gas emissions measures progress towards reduction targets. The methodology for agriculture has recently changed to better reflect the current science on the GHG emissions from agriculture.

The new methodology is called the ‘smart inventory’. It includes a wider range of technologies and management options than the previous inventory based on more recent science, although there are still gaps in our understanding.

This report summarises how different changes to  agricultural practice in Scotland are (or could be) recognised in the smart inventory. It provides information to policy makers on what changes can be captured in the UK GHG inventory, and what further steps could be taken to reflect Scottish agricultural practices more accurately.

Key findings

  • The smart inventory reflects the mitigation activities for which we currently have robust data and analysis
  • Annual Scotland-specific data are used in many activities (e.g. crop areas, fertilisation rates livestock numbers, milk yield, slaughter weight), but more specific activity data either are either not updated annually or not systematically collected for Scotland.
  • Inventory development is a continuous process and future data collection should be planned with the Inventory team in order to maximise the use of the data in the inventory. 
  • There are four main data categories that would enhance data collection initially:
    a) Nitrogen fertilisation of minor crops and novel legumes 
    b) Area and fertilisation information on  intercropping
    c) Ruminant diets
    d) Manure management and storage information