Mitigation of greenhouse gas emissions from the whole farm.

Greenhouse gases (GHG: carbon dioxide, CO<sub>2</sub>; methane, CH<sub>4</sub>; and nitrous oxide, N<sub>2</sub>O) are produced as part of the carbon (C) and nitrogen (N) cycle on farms. Livestock production, N fertilizer use and rice cultivation are the main farm activities producing CH<sub>4</sub> and N<sub>2</sub>O, while CO<sub>2</sub> emissions are due to land use change. Farming in Asia, Africa and South America contribute 75% of global GHG emissions. Consideration of emission scaled by unit of product such as milk, meat, or grain (GHG intensity) is important when assessing mitigation practices, which should target: reduction in CH<sub>4</sub> emission from enteric fermentation and from manure storage; reduction in N<sub>2</sub>O emissions from soils and CH<sub>4</sub> emissions from rice paddies; increase in C uptake and storage on farms. Improved production efficiency of ruminant livestock on farms results in decreased GHG intensity because more production and lower manure volumes are obtained from fewer animals. Direct interventions can also be made to reduce enteric CH<sub>4</sub> emissions, such as feeding additives or compounds interfering with microbial processed that result in CH<sub>4</sub> production. Reducing CH<sub>4</sub> emissions by changing the form of manure stored from liquid to solid; preventing methanogenesis; and capturing the CH<sub>4</sub> through covers and flaring or anaerobic digestion; are recommended. Increasing organic matter input to soils or reducing decomposition rates by various practices partly can offset farm level GHG emissions. Management of N fertilizer, and alternative wetting cycles in rice paddy cultivation can reduce N<sub>2</sub>O and CH<sub>4</sub> emissions from soils, respectively. Management packages that consider regional needs, synergies and trade-offs for whole-farm GHG emission reduction need to be developed.