Transforming nitrogen without carbon How much carbon does it take to make nitric acid? The counterintuitive answer nowadays is quite a lot. Nitric acid is manufactured by ammonia oxidation, and all the hydrogen to make ammonia via the Haber-Bosch process comes from methane. That's without even accounting for the fossil fuels burned to power the process. Chen et al. review research prospects for more sustainable routes to nitrogen commodity chemicals, considering developments in enzymatic, homogeneous, and heterogeneous catalysis, as well as electrochemical, photochemical, and plasma-based approaches. Science , this issue p. eaar6611