Editor's Note: Sierra Energy is one of seven private companies Inc. identified that are driving development within seven key pathways to net zero--eliminating one ton of greenhouse gases for every ton emitted.

AMERICANS DUMP HALF of the 292.4 million tons of trash we generate every year into landfills, where rotting waste vents methane. Or we incinerate it, trading every ton of garbage for almost half a ton of atmospheric carbon dioxide. (We recycle less than a quarter of it.) But if you could turn that waste into power efficiently, you'd have the very definition of sustainable energy. That's the promise of Sierra Energy, an emerging leader in a technology called gasification: vaporizing organic waste--anything containing carbon--and turning it into fuel, without actually burning it.

Former consultant Mike Hart, 60, bought the patents to Sierra's gasification process nearly 20 years ago. Hart is an entrepreneur with flair: He once invented Hawaiian shirt-inspired neckwear and called it the Mai-Tie. He launched Sierra Energy in 2004, and has been working to commercialize gasification ever since.

Under Hart, Sierra developed a system called FastOx, which feeds garbage into the top of a chamber that looks like a closet-size lava lamp. Sierra's proprietary lances--one of its key inventions--inject oxygen and steam into the vessel's base, catalyzing exothermic (meaning energy-releasing) chemical reactions in the rubbish. That generates extreme heat, reducing the amount of outside power needed to keep the process going. As the waste keeps getting hotter, it breaks down, and when matter reaches temperatures of 2,200 degrees Celsius, it can take only a few elemental forms. The carbon turns into a char that interacts with the oxygen and steam to create syngas, essentially a mix of hydrogen and carbon monoxide vapors. And syngas can be used as fuel or repurposed into other carbon-based compounds. The beauty is the gasifier runs on energy in the waste itself.

The U.S. military was an early believer in this waste-to-gas process. The Department of Defense helped fund Sierra's technology for the first time in 2009. And since 2020, it's had Sierra demonstrating how it will handle waste at Fort Hunter Liggett, an Army training center in Jolon, California. A quarter-acre-size FastOx operation there is capable of gasifying 10 tons of trash and producing about 40 gallons of diesel fuel a day or generating about 250 kilowatts of electricity per hour.

Sierra secured its first round of venture financing in 2019, and aims to boost its gasifiers' capacity to 100 tons a day. Hart imagines a not-too-distant future in which communities gasify 100 percent of their waste and generate their own fleet fuel. "They'd have a negative carbon footprint," he says, "plus a cost savings."

Sierra plans to issue its first commercial licenses this year, and according to Hart, it already has 8,000 inquiries on gasifiers.