Agricultural methane emissions and the potential formitigation

Agriculture is the largest anthropogenic source of methane (CH4), emitting 145 Tg CH4 y−1 to the atmosphere in 2017. The main sources are enteric fermentation, manure management, rice cultivation and residue burning. There is significant potential to reduce CH4 from these sources, with bottom-up mitigation potentials of approximately 10.6, 10, 2 and 1 Tg CH4 y−1 from rice management, enteric fermentation, manure management and residue burning. Other system-wide studies have assumed even higher potentials of 4.8–47.2 Tg CH4 y−1 from reduced enteric fermentation, and 4–36 Tg CH4 y−1 from improved rice management. Biogas (a methane-rich gas mixture generated from the anaerobic decomposition of organic matter and used for energy) also has the potential to reduce unabated CH4 emissions from animal manures and human waste. In addition to these supply side measures, interventions on the demand-side (shift to a plant-based diet and a reduction in total food loss and waste by 2050) would also significantly reduce methane emissions, perhaps in the order of greater than 50 Tg CH4 y−1. While there is a pressing need to reduce emissions of long-lived greenhouse gases (CO2 and N2O) due to their persistence in the atmosphere, despite CH4 being a short-lived greenhouse gas, the urgency of reducing warming means we must reduce any GHG emissions we can as soon as possible. Because of this, mitigation actions should focus on reducing emissions of all the three main anthropogenic greenhouse gases, including CH4.