Agriculture has been set a challenging sectoral target of reducing greenhouse gas (GHG) emissions by 25% or 5.75 Mt CO2e by 2030. The ammonia (NH3) targets also pose considerable challenges, with reductions in emissions from the current 120kT of NH3 to 112kT NH3 needed by 2030. Many of the technologies will reduce both GHG and ammonia emissions.

In order to reduce on-farm emissions, there are some steps farmers can take. Nitrogen and methane emissions are the focus of the top tips outlined below.

Reduce nitrogen (fertiliser and manure) emissions

Reducing fertiliser use can both reduce GHG and NH3 emissions and improve margins. The main fertiliser reduction strategies are:

1Get soil fertility correct

Moving from pH 5.5 to 6.3 can make 50-70 kg N/ha per year available from the soil to the crop, as well as reducing nitrous oxide (N2O) emissions per kg of N applied.

2 Use legumes or multi-species swards

Clover can fix between 80-120kg N/ha per year, depending on underlying soil fertility and sward management. Multi-species swards also offer extra benefits in terms of drought resistance and cow health.

3 Apply slurry using LESS

Slurry nitrogen fertiliser replacement value can be increased (and ammonia emissions reduced) by between 25% and 50% by using a trailing hose (dribble bar) or trailing shoe technology. However, for these measures to work, N fertiliser application must be decreased by the amount of N that each measure saves, otherwise there is little or no GHG emissions saving.

If mineral fertiliser must be applied, then switching from either CAN and straight urea to protected urea will directly reduce both GHG and NH3 emissions. New research on low-emission compound fertilisers has found that N2O emissions could be reduced by around 40%.

Reduce enteric and manure methane and NH3

Methane accounts for 70% of agricultural GHG emissions, which is split between methane from enteric fermentation (87%) or animals belching and manure methane (13%) .

Tips to reduce methane emissions from slurry storage

  • Acidification with hydrochloric acid or ferric/aluminium chlorides to pH <6 has been shown to reduce both methane and NH3 by 86% and 98%, according to new research investigating the efficacy of a range of manure additives and acidifying compounds on reducing emissions.
  • Lower cost alternatives, such as dairy washings or grass silage effluent (at a 7% inclusion rate), have shown a 50-60% reduction in methane, although reductions in ammonia emissions were much lower.
  • Covering external stores. This measure reduces NH3 emissions by between 40% for floating covers, 60% for flexible covers and 80% for tight lid covers.
  • Aeration can also reduce methane by up to 50%. However, NH3 emissions can be significantly increased depending on the aeration system being used.
  • In terms of reducing enteric methane, ongoing research is showing that:

  • Increasing genetic merit via EBI reduces GHG emissions per unit of product by 2% for every €10 increase in EBI.
  • Feed additives can reduce methane.
  • Where animals are slaughtered at an earlier age, the total amount of methane produced on an annual basis is reduced and could account for up to 0.8mt of carbon dioxide equivalents per year.
  • Increasing time at grass can also reduce enteric methane, as results are showing that the methane emissions factor during grazing is reduced from 6.5% to 5.75% of gross energy intake.