Practical paths towards quantifying and mitigating agricultural methane emissions

This review summarizes the rapid advances in direct practical methods to quantify and reduce agricultural methane emissions worldwide. Major tasks are location, identification, quantification and distinction between different specific sources (often multiple emitters such as manure pools, animal housing, biodigesters and landfills are co-located). Emission reduction, facilitated by developing methodologies for locating hot spots, is the least-cost choice for action, especially from manure stores, biodigesters and from controlling biomass burning. Agricultural methane can also be used to generate electricity or, in appropriate circumstances, can be destroyed by oxidation. It may be possible to cut North American, East Asian and European emissions sharply and rapidly. In Africa and South Asia, emissions from crop waste and food waste in landfills, also a source of air pollution, can be sharply and quickly reduced. Globally, cutting total annual agricultural and waste emissions by a third would demand reductions of very approximately 75 Tg yr−1. Apportioned by source type, notional cuts might be 30–40 Tg yr−1 from livestock and manure, 5-10 Tg yr−1 from rice cultivation and 20 Tg yr−1 or more from specifically agricultural waste.