Environmental and economic assessment of the formic acid electrochemical manufacture using carbon dioxide: Influence of the electrode lifetime

Abstract

This paper focuses on the study of the environmental and economic feasibility of the formic acid (FA) synthesis by means of electrochemical reduction (ER) of carbon dioxide (CO2) with special emphasis on the cathode lifetime. The study has used a Life Cycle Assessment (LCA) approach in order to obtain the environmental indicators as Global Warming Potential (GWP) and Abiotic Depletion (ADP) (both elements and fossil resources ADPs). The values of the indicators obtained in the assessment were representative of the Carbon Footprint (CF) and resource savings of this fabrication process. The commercial/conventional process for FA production was used as benchmark. The novelty of the study is the incorporation into the Life Cycle Inventory (LCI) of those materials and chemicals that are used in the fabrication of an ER cell, and in particular in the cathode. Hence, the lifetime of the cathode was used as a main parameter. The results obtained for a baseline case demonstrated that cathode lifetimes over 210 h would be enough to neglect the influence of the cathode fabrication from an environmental perspective. A first approach to the utility costs of CO2 ER process was also proposed in the study. Cost of utilities ranged between 0.16 € kg and 1.40 € kg-1 of FA in an ER process compared with 0.21 € kg-1 and 0.43 € kg-1 of FA in the conventional process depending on the market prices. This study demonstrated that the ER-based process could be competitive under future conditions if a reasonable electrocatalytic performance (in terms of cell voltage, current density, and faradaic efficiency) is achieved within a reasonable medium or long-term horizon. The results obtained aim to provide useful insights for decision-makers on the future developments within a decarbonized chemical industry.