Reduction of Greenhouse Gas Emissions at Farm and Manufacturing Levels PRICE : 48 Euro

The most important greenhouse gases (GHG) generated by the dairy industry are methane (CH4), nitrous oxide (N2O), carbon dioxide (CO2) and some refrigerants (CFCs and HFCs). At a global level, the share of GHGs emitted is: CO2 64%, CH4 20%, CHF 10%, N2O 6%. Enteric fermentation by dairy cows is only responsible for 3% of the global warming in the world. In a ruminant, methane is naturally produced as a result of the microbial fermentation process in the rumen. The amount of methane produced depends on the quality and quantity of feed ingested by the cow. The decomposition of organic components and nitrogen in animal manure can also produce CH4 and N2O. When stored as a liquid, manure tends to produce more CH4, and when handled as a solid it tends to produce more N2O. N2O is naturally emitted from agricultural soil as a result of the process of denitrification and nitrification, partly due to nitrogen fertilisers. However, there is considerable uncertainty around the estimates of emission from dairy farms, due to the scant availability of data to document the variability that exists at the farm scale. Part of the problem is the difficulty in measuring emissions from livestock facilities and fields. CO2 is emitted mainly at the manufacturing level due to energy consumption required by the process used, but also at the farm level with the consumption of fossil fuels. Emissions of refrigerant gases from the refrigerating system in the factory can also occur. The evaluation of GHG emission in the dairy industry must consider not only the dairy farm and the manufacturing process, but incorporate the other indirect contributors that have emitted gases during their production (fertiliser, transport, etc.). For instance, a comparison was made between very different conventional French dairy farm systems, on a whole farm approach but without the carbon storage. The average estimated emission found is around 1 kg CO2 per litre of milk, with very little difference in the total between different farm systems. It is also important to keep in mind that grassland could also store carbon and that sequestration could partly balance the emissions. 2.1. Nature of the Four Gases Emitted and their Share The dairy industry contributes directly to emissions of greenhouse gases through a variety of processes.The most important greenhouse gases (GHG) generated by the dairy industry are methane (CH4), nitrous oxide (N2O), carbon dioxide (CO2) and some refrigerant emissions (CFCs and HFCs). At a global level, the share of GHGs emitted is : CO2 64%, CH4 20%, CHF 10%, N2O 6% (figure 1). Nitrous oxide has a very high global warming potential (310 times higher than CO2), and accounts for 6% of emissions of GHG at the world level. Agriculture contributes almost 80% of the N2O emissions. Importantly, methane has a global warming potential around 20 times higher than that of carbon dioxide. So even if the absolute emission of CH4 are a lot less than the CO2 emissions, it still accounts for 20% of the contribution to global warming in the world. Agriculture is responsible for about 50% of total CH4 emissions, with around three-quarters of this coming from rice growing and livestock activities (Moss et al., 2000). At the word level, the growing of rice is an important source of CH4, but in Europe virtually all the CH4 emissions come from livestock, and especially the enteric fermentation of ruminants (87%) and from manure (11%). 1 Centre National Interprofessionnel de l’Economie Laitière (CNIEL), 42 rue de Chateaudun, 75314 , F-Paris cedex 09, e-mail: sophie.bertrand@inst-elevage.asso. fr 1 : Institut de l’Elevage, 9 rue André Brouard, BP 70510, F-Angers cedex 02, e-mail: sylvie.hacala@inst-elevage.asso. fr