By Laura Legere, Pittsburgh Post-Gazette.

Gas from garbage can be a useful waste.

Methane created by decaying organic material in Pennsylvania landfills has been used in greenhouses; in asphalt plants; to produce electricity at a prison; and to generate steam for turning potatoes into dehydrated potato flakes.

Now a rule proposed by the U.S. Environmental Protection Agency might spur new landfill gas-to-energy projects, if the business case for using the gas is more compelling than burning it off.

On Aug. 14, EPA announced two proposals that would lower the emissions threshold by nearly a third for when new or existing landfills have to begin collecting and controlling landfill gas rather than just letting it seep into the atmosphere.

The rule is more about environmental protection than energy development: methane is a potent greenhouse gas and landfills were responsible for 18 percent of the human-caused methane emissions in the U.S. in 2013, making it the third largest methane source after ruminant livestock and leaky oil and gas systems.