Methane menace

Methane emissions are something usually associated with agricultural feed lots. So researchers were somewhat surprised to find that the Los Angeles area is emitting more than twice the amount of methane than was expected.

Estimates from the California Air Resources Board determined that human activity in Los Angeles should account for about 260,000 tons of methane each year. But researchers from the California Institute of Technology found emissions of about 600,000 tons, according to an article in Discovery News.

Methane is a greenhouse gas that’s 25 times more powerful than carbon dioxide. In L.A., much of it comes from burning natural gas, which is made mostly of methane. “Approximately 10.5 million tons of natural gas was shipped into the south coast air basin in 2006; if 2 to 3 percent of that is leaking into the atmosphere, it could account for a large part of the discrepancy,” the article reported. It could also be coming from vehicle exhaust pipes, sewage treatment plants or landfills.

The study may help turn an eye on urban methane emissions, long overshadowed by its agricultural counterpart.