Committee on Climate Change

Emissions from Agriculture

There are two main sources of non-CO₂ Greenhouse gases (GHGs) in the agriculture sector, which together account for around 9% of total UK GHG emissions:

• Nitrous oxide resulting from fertiliser use on agricultural soils – 55% of total agriculture emissions. The nitrogen within fertiliser is crucial to ensuring agricultural productivity, however, when excess nitrogen remains in the soil, in certain conditions it is converted to nitrous oxide (N₂O) and is released into the atmosphere as a harmful GHG
• Methane from the digestive process of livestock (enteric fermentation) and from manure – 36% of total agriculture emissions. Methane is released through the digestive processes whereby cattle and sheep (ruminants) break down hard-to-digest grassy materials and produce methane, mostly through burping as the cud is re-chewed, as well as from animal manures.

Estimated agriculture emissions, which are primarily of non-CO₂ greenhouse gases, fell slightly in 2009, which is the most recent year for which data is available. In the longer term, emissions have fallen by around 21% since 1990, reflecting changes in agricultural activity:

• Livestock numbers have fallen as a result of reform to the EU Common Agricultural Policy (CAP), which has decoupled farming subsidies from production levels
• The quantity of fertiliser applied to agriculture land fell, particularly on pasture land, which may reflect lower stocking densities as a result of CAP reform
• There is some evidence of improved efficiencies in livestock production and fertiliser practices, neither of which may be wholly captured in the UK GHG Inventory

Estimates of UK agricultural emissions include significant uncertainties. The inventory for agriculture is calculated using default IPCC emissions factors in the absence of better country-specific emissions factors that reflect regional conditions such as climate, soil quality and farming practices The Government has committed to investing in the agriculture evidence base to better understand and measure emissions from farming systems and develop a more accurate inventory that can reflect mitigation activities. This work is due to complete in 2015.

Going forward, there is significant untapped potential to reduce emissions further from this sector, for example, from improving the process by which livestock are fed in order to reduce emissions.