Towards Sustainable Oxalic Acid from CO₂ and Biomass

To quickly and drastically reduce CO₂ emissions and meet our ambitions of a circular future, we need to develop carbon capture and storage (CCS) and carbon capture and utilization (CCU) to deal with the CO₂ that we produce. While we have many alternatives to replace fossil feedstocks for energy generation, for materials such as plastics we need carbon. The ultimate circular carbon feedstock would be CO₂. A promising route is the electrochemical reduction of CO₂ to formic acid derivatives that can subsequently be converted into oxalic acid. Oxalic acid is a potential new platform chemical for material production as useful monomers such as glycolic acid can be derived from it. This work is part of the European Horizon 2020 project "Ocean'' in which all these steps are developed. This Review aims to highlight new developments in oxalic acid production processes with a focus on CO₂-based routes. All available processes are critically assessed and compared on criteria including overall process efficiency and triple bottom line sustainability.