Options to reduce greenhouse gas emissions from enteric fermentation and manure handling in dairy farming – An analysis based on farm network data

In the project "Climate Effects and Sustainability of Organic and Conventional Farming Systems" 44 paired organic and conventional dairy farms in Germany were analysed for their greenhouse gas (GHG) emissions from enteric fermentation and from animal excretions in the stables, on the pastures and during storage of manure. In milk production, methane (CH4) from enteric fermentation of the cows is the dominating GHG source. On the analysed farms the calculation results for CH4 emissions were strongly dependent on the choice of methodology. Considering crude nutrient contents of the actual feed rations, as opposed to using dry matter intake, generally increased the level of the results and widened their range. This was particularly prominent at lower milk yields when high amounts of fibre rich feed stuff were used. Since feed quality management on farms is crucial for both milk yield and CH4 emissions from enteric fermentation, it should be of high importance in advisory concepts that aim at reducing GHG–emissions in milk production. Just like CH4 emissions from enteric fermentation, GHG emissions from dairy manure are also directly connected with the feed intake and feed quality. Technical changes in manure storage and handling (e.g., integration of biogas plants) offer high GHG reduction potential in dairy farming.