Greenhouse gas mitigation in agriculture

Agricultural lands occupy 37% of the Earth’s land surface. Agriculture accounts for 52% and 84% of global anthropogenic methane and nitrous oxide emissions. Agricultural soils may also act as a sink or source for carbon dioxide (CO2), but the net flux is small. Many agricultural practices can potentially mitigate greenhouse gas (GHG) emissions, the most prominent of which are improved cropland and grazing land management and restoration of degraded lands and cultivated organic soils. Lower, but still significant mitigation potential is provided by water and rice management, set-aside, land use change and agroforestry, livestock management and manure management. The global technical mitigation potential from agriculture (excluding fossil fuel offsets from biomass) by 2030, considering all gases, is estimated to be ~5500-6000 megatonnes (Mt) CO2-eq. yr-1, with economic potentials of ~1500-1600, 2500-2700, and 4000-4300 Mt CO2-eq. yr-1 at carbon prices of up to 20, up to 50 and up to 100 US$ t CO2-eq.-1, respectively. In addition, GHG emissions could be reduced by substitution of fossil fuels for energy production by agricultural feed stocks (e.g. crop residues, dung, dedicated energy crops). The economic mitigation potential of biomass energy from agriculture is estimated to be 70-1260 Mt CO2-eq. yr-1 at up to 20 USD t CO2-eq.-1, and 560-2320 Mt CO2-eq. yr-1 at up to 50 USD t CO2-eq. There are no estimates for the additional potential from top down models at carbon prices up to 100 USD t CO2-eq.-1, but the estimate for prices above 100 USD t CO2-eq.-1 is 2720 Mt CO2-eq. yr-1. These potentials represent mitigation of 5-80%, and 20-90% of all other agricultural mitigation measures combined, at carbon prices of up to 20, and up to50 USD t CO2-eq.-1, respectively.