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

In the 2018 Climate Change Plan, the Scottish Government committed to a reduction in emissions from the use of synthetic nitrogen fertiliser, which currently accounts for around 25% of the GHG emissions from agricultural soils. One approach is to increase cultivation of nitrogen-fixing crops also known as legumes, which convert nitrogen from the air into a form that is biologically useful.

The evidence base for the effectiveness of nitrogen fixing crops is largely based on research and experience at a UK and European level. ClimateXChange was asked by Scottish Government to explore the current state of confident knowledge for their application, and their potential benefits for farm business (commercial as well as on-farm) under Scottish circumstances (i.e. soil, climate, markets, etc). 

80% of current demand for legume products in Scotland is imported, mainly for animal feed, but also for human consumption.

There is a long history of growing legumes in Scotland and a considerable potential to increase legume production. However, there is limited opportunity to access commercial seed stock as current markets are focused on more-temperate climates, and there is also a lack of processing facilities in Scotland.

An increase in legumes grown in place of another crop as part of a rotation and with no added fertiliser, could give significant savings in terms of fertiliser-offset depending on the crop.

Farm-based carbon audits are one of the tools that might help reduce greenhouse gas emissions in the farming sector. This report compares the available tools to assess their potential application in Scotland.

Key findings:

• 64 potentially applicable tools were identified through a web search. Of these, nine were selected for more detailed comparison. Analysis found that a further six were not suitable due to a variety of shortcomings (e.g. general purpose of the tool, major limitations in comprehensiveness, lack of transparency).
• Only three of those tools would be suitable for farm level carbon audits in Scotland:
  1. AgRE Calc
  2. Cool Farm Tool and
  3. Solagro (JRC) Carbon Calculator
• These tools follow a similar calculation framework (international guidelines and international calculating standards), although none can be judged to be fully comprehensive. Although currently free to use, maintenance and development of the carbon audit framework requires continuing investment. In addition, their application needs to be embedded in wider environmental and farm context in the form of advisory support (i.e. the tool should not be the sole information source for decision).
• The comprehensiveness and practicality of each tool varies between production systems (e.g. crop production, livestock production, carbon sequestration). No tool is fully comprehensive, and each can only handle a limited amount of possible emissions reductions on farms. None of the three recommended tools considers embedded emissions in livestock bought in.

Soil carbon, or the content of carbon housed within soil, plays a significant role in the release and absorption of global greenhouse gas emissions. Changes in land use contribute to release of this carbon, and Scottish Government is interested in the potential implications of such change across several policy areas.