Given how much carbon dioxide has been released into the atmosphere from fossil fuels, replacing those fuels with clean options like nuclear energy is urgent, but could be likened to shutting the barn door after the proverbial horse has bolted. But what if you could also round up excess CO₂ already in the atmosphere? That’s the goal of direct air capture (DAC) and other so-called negative emission technologies—to capture climate warming CO₂ for use in products or processes or for permanent storage.