Takoma Park, Maryland—On an exceptionally frigid day in this Washington, D.C., suburb, a modest black stove in the Ikle-Khalsa family's living room was keeping the house warm. Every few seconds, it emitted a low grinding sound as a motor pushed more fuel into the fire.

The stove runs on dried corn kernels, which Sat Jiwan Ikle-Khalsa hauls by the bucketful from a communal bin a mile and a half away. He manages a small cooperative where members pay a fee to access the hopper, which sits on city land, and use an honor system to record their withdrawals.

The Save Our Sky co-op bills corn as an inexpensive heat source that's low in heat-trapping carbon emissions and supports a local