Agriculture and the greenhouse gas emissions: A literature review

Agriculture contributes to the greenhouse effect by increasing carbon dioxide, nitrous oxide and methane emissions. This literature review examines agricultural sources and sinks of greenhouse gases as well as factors affecting emissions. Options for mitigating emissions are presented as well the results of greenhouse gas emission measurements on Finnish agricultural soils. In addition, some basic information is given about Finnish agriculture, and the estimation of emissions using the IPCC Guidelines is described. Carbon dioxide sources include decomposition of soil organic matter, combustion and liming. The agricultural sector can mitigate CO2 emissions by increasing carbon stocks in soils and vegetation, reducing fossil fuel consumption, and increasing the production of bioenergy. There is little opportunity to decrease the amount of liming in Finland. The main nitrous oxide sources are nitrification and denitrification. N2O emissions can be reduced by enhancing plants' ability to compete for soil nitrogen and by keeping the rate of emission processes as low and the duration of emissions as short as possible. Special attention should be paid to manure management because manure contains abundant nitrogen that can be lost as N2O. Improvements in the protein feeding of livestock could also reduce potential N2O emissions from manure. Methane is emitted, for example, in the course of enteric fermentation and the anaerobic decomposition of organic matter in manure. The emission of CH4 from soils depends on the relative amounts of methane production and consumption. Cattle with high productivity emit less methane per unit of milk or meat than do animals with low productivity. The number of breeding animals could be reduced by improving animal reproduction efficiency. Methane emitted from manure should be utilized as an energy source, or the formation of it should be prevented by keeping manure under aerobic conditions