Can conversion of CO2 into fuels via electrochemical or thermochemical reduction be energy efficient and reduce emissions?

Abstract

Electrochemical and thermochemical conversion of CO2 into fuels are significant carbon conversion technologies to mitigate carbon emissions. Based on the captured CO2, many previous studies carried out tech-economic and environmental analyses for the CO2 conversion systems. However, it is unclear about the energy efficiency and emission reduction of the full-chain system after applying carbon conversion technologies to the carbon sources such as coal power plants and chemical industries. With a unified coal-fired power plant as the carbon source, this study conducted a full-chain systematic analysis of three representative CO2 conversion technologies (shown as routes 1, 2, and 3). Routes 1, 2, and 3 converted the emitted CO2 into fuels via CO2 electrolysis, MEA-CO2 electrolysis, and CO2 hydrogenation. The performance of three Routes in terms of energy efficiency and carbon emissions was comprehensively analyzed. And this work also investigated the energy efficiency improvement potential of three Routes. The results indicated that the energy efficiency of Route 1 was the greatest. And Route 2 exhibited optimal emission reduction. The core factors for enhancing the performance of full-chain systems were improving the efficiency of photovoltaic power generation and developing low-energy-consumption CO2 absorbents. The results also indicated that to date, from the perspective of converting CO2 into the fuel gas CO, no Routes had advantages over coal power plants with carbon capture and storage (CCS) or syngas production directly from coal gasification in terms of energy efficiency and carbon emissions. However, converting CO2 into high-value-added products might be more significant for integrating carbon emission reduction and storing renewable electricity.