Washington, D.C. ? A vast new energy supply in hard-to-tap older oil fields may be generated simply by feeding fertilizer to some deep-dwelling, gas-making microbes, new research suggests.

Canadian and English researchers were able to convert oil into usable methane in small glass tubes during two years of lab research, instead of a process that takes tens of thousands of years underground. The next step is to do it in real oil fields.

The new method takes advantage of the natural process that occurs when microbes slowly degrade oil into methane, the chief ingredient in natural gas.

The researchers report their experiment in a study published online Wednesday in the journal Nature.

“You’re talking a very substantial amount of energy,” said study co-author Steve Larter, a University of Calgary petroleum geologist. “It’s potentially a game-changer if it can be demonstrated.”