Agroecosystem greenhouse gas balance indicator: Methane component
Methane emissions from agroecosystems in Canada were estimated for 1986 and 1991. The principle source of CH4 was from livestock production. According to these estimates, farm animals produced about 639 kt of CH4 during 1986 and 681 kt of CH4 during 1991. An additional 203 and 209 kt of CH4 were also emitted from animal manures in 1986 and 1991, respectively. The regional magnitude of these sources is presented in kg CH4/km2 for both eastern and western Canada. Agricultural soils, which can either be a source or a sink of CH4 depending on the soil moisture conditions, were estimated to emit about 12 kt CH4/yr and absorb 7 kt CH4/yr. Burning of fossil fuels on farms produced about 1 kt CH4/yr. Overall, the net CH4 emissions from agroecosystems during 1986 and 1991 were estimated to be 848 kt and 896 kt, respectively. For a 100 year time horizon, the total CH4 emissions during 1986 and 1991 were equivalent to 17.8 and 18.8 million tonnes of CO2, respectively.