California regulates cow farts
Despite strong opposition from farmers, Gov. Jerry Brown signed legislation in September that for the first time regulates heat-trapping gases from livestock operations and landfills.
Cattle and other farm animals are major sources of methane, a greenhouse gas many times more potent than carbon dioxide as a heat-trapping gas. Methane is released when they belch, pass gas and make manure.
"If we can reduce emissions of methane, we can really help to slow global warming," said Ryan McCarthy, a science adviser for the California Air Resources Board, which is drawing up rules to implement the new law.
Livestock are responsible for 14.5 percent of human-induced greenhouse gas emissions, with beef and dairy production accounting for the bulk of it, according to a 2013 United Nations report.
