Techno-economic assessment of non-aqueous CO2 reduction

Most research on low-temperature CO2 electrolysis has focused on aqueous electrolytes, primarily because non-aqueous systems require high cell voltages. However, CO2R in aqueous electrolytes competes with hydrogen evolution and requires many electron transfers to produce C2+ molecules, challenges that can be suppressed in non-aqueous electrolytes. In this forward-looking techno-economic assessment, we model the product cost for non-aqueous CO2R. We show that CO2R to oxalic acid – a 2-electron C2 product formed in non-aqueous electrolytes – is surprisingly affordable, although producing CO is more expensive in non-aqueous systems. Using parameters extracted from the largest collection of literature data on CO2R in aprotic non-aqueous electrolytes, we find that oxalic acid would cost $2.87/kg in a small-scale process. A commercial-scale plant would lower the product cost to $1.56/kg, approaching current market prices of $0.7 to $2.5/kg. Capital cost for this process is dominated by product separation, while operating costs mostly arise from stack replacement and electricity to drive the high required cell voltage. This assessment shows that non-aqueous CO2R could be a promising pathway for scale-up that has been largely overlooked compared to aqueous CO2 electrolysis, offering new opportunities like electrolyte design to lower product costs. We therefore present a technical roadmap to make non-aqueous CO2R to oxalic acid competitive with market prices.