The astonishing reserves of fossil-based natural gas on the North American continent—100 years of supply for the U.S. and 200 years for Canada—combined with the rapid growth in market share of renewable sources would seem to lock in the energy equation: wind plus solar equals power generation.

Except when the wind doesn’t blow—or blow sufficiently—and the sun doesn’t shine. When that happens, natural gas-fired generation fills in the gaps.

That might preclude the need to pursue other sources of renewable energy, but the U.S. Environmental Protection Agency (EPA), wary of the challenge of methane leaks along the gas value chain, has its eye on other solutions, including renewable natural gas or biogas.

“Biogas has been captured and used for energy for a long time, for decades both here in the U.S. and around the globe,” said Chris Voell of the EPA’s climate change division. “Traditionally it’s been used for electricity production. Oftentimes that’s where the incentives were placed so that’s where people had direction.”