Upgrading CO ₂ with methane: The use of carbon dioxide as a reactant could help to mitigate its impact on climate, but it is difficult to activate as an oxidant. Buelens et al. combined methane in a high-temperature “super-dry” reforming process that generates reactive carbon monoxide. Both molecules were fed into a reactor containing a nickel methane-reforming catalyst, an iron oxide solid oxygen carrier, and calcium oxide as a CO ₂ sorbent. The adsorbed CO ₂ was treated with an inert gas purge that shifted the equilibrium, releasing mainly CO. This isothermal process avoids carbon buildup and can be used with biogas methane that contains substantial levels of CO ₂ . Science , this issue p. 449