Enteric fermentation and ruminant eructation: the role (and control?) of methane in the climate change debate

Anthropogenic processes are responsible for between 55% and 70% of the estimated 600 Tg of methane that is released annually into the atmosphere, with enteric fermentation a major contributor to emissions in a number of countries. This paper therefore reviews current levels of CH4 discharges by both animal type and country, and shows how the growth or decline in national herds over the last 20 years has significantly altered the global composition of enteric emissions. As developing countries are now responsible for almost three-quarters of such emissions, this has important implications in terms of mitigation strategies—particularly as such countries are presently outside the remit of the Kyoto Protocol.