At the rate at which we’re harvesting fish from the ocean, we may not have enough food to feed farmed fish, let alone humans. That’s why a startup is replacing fish food with something more sustainable: microbes grown with carbon dioxide. The startup feeds carbon dioxide to microbes that can then become proteins for companies that make pellets of food for fish. Because carbon dioxide emissions are free, the process is also cheaper than catching fish to turn into fish meal. It’s a win-win for the environment and for business.