Across the U.S., abandoned wells are belching the powerful greenhouse gas. This nonprofit aims to plug them to fight global warming.

TOOLE COUNTY, Mont. — The stench bellows from the 1,500-foot hole in the ground, the remains of a well long ago abandoned by a bankrupt oil company. Despite its rotten-egg smell, the culprit is methane, and every year this single well spews the potent greenhouse-gas equivalent of roughly 600 cars

It has been gushing, unchecked, for nearly three decades.