Former SpaceX rocket scientist and pilot Brad Hartwig once dreamed of going to space. Now he’s focused on a different moonshot. Arbor, the startup he founded in 2022, has developed a system premised on oxy-combustion—the same process that powers rocket engines—to convert organic waste from agriculture, forestry, and food into low-cost energy, while capturing the carbon that’s generated and burying it underground. The process also emits clean water, which can be reused. The shipping-container sized power systems are capable of producing five megawatts each per year, enough to power 4,000 homes. “We’re leveraging all this technology that our team pioneered at SpaceX and repurposing it,” Hartwig says. Arbor recently announced a partnership to sell carbon credits to Microsoft starting in 2027.