USDA Study Shows Livestock Methane Emissions were Significantly Underestimated

A new study has found that a 2011 estimate of methane emissions generated by the planet’s livestock was incorrect, with the new finding indicating that they were actually 11 percent higher than the numbers used by the Intergovernmental Panel on Climate Change (IPCC), leading to the guidelines and targets set out in the Paris climate accord. Methane (CH4) is produced from the decomposition of biological matter, such as livestock manure, and is a potent greenhouse gas, retaining up to 86 times more heat energy than the same mass of carbon dioxide over a 20-year period.

The study, conducted by the U.S. Department of Agriculture (USDA), explained that the original estimates lacked direct measurements for certain sources of methane emissions, resulting in an overall lower number for the world’s output. This new study "created new per-animal emissions factors — that is measures of the average amount of CH4 discharged by animals into the atmosphere — and new estimates of global livestock methane emissions."

"In many regions of the world, livestock numbers are changing, and breeding has resulted in larger animals with higher intakes of food," explains senior study author, Dr. Julie Wolf, with the USDA’s Agricultural Research Service (ARS). "This, along with changes in livestock management, can lead to higher methane emissions."

The study found that as developing countries become more affluent, they produce more livestock, and in turn, more methane is produced, with the most rapid increases over recent decades being seen in Asia, Latin America and Africa. Increases were more moderate in the U.S. and Canada, and declined slightly in Western Europe.

All livestock species will produce methane through their fecal matter, but ruminants — animals that ferment their food in specialized stomachs, such as cows, goats and sheep — produce extra methane through this fermentation process. Cattle, both beef and dairy, are the largest producers by far, by virtue of both the size of the individual animals (compared to goats and sheep), and the sheer number of cattle that are raised globally.