Comparative energetic assessment of methanol production from CO2: Chemical versus electrochemical process

Emerging emission-to-liquid (eTL) technologies that produce liquid fuels from CO2 are a possible solution for both the global issues of greenhouse gas emissions and fossil fuel depletion. Among those technologies, CO2 hydrogenation and high-temperature CO2 electrolysis are two promising options suitable for large-scale applications. In this study, two CO2-to-methanol conversion processes, i.e., production of methanol by CO2 hydrogenation and production of methanol based on high-temperature CO2 electrolysis, are simulated using Aspen HYSYS. With Aspen Energy Analyzer, heat exchanger networks are optimized and minimal energy requirements are determined for the two different processes. The two processes are compared in terms of energy requirement and climate impact. It is found that the methanol production based on CO2 electrolysis has an energy efficiency of 41%, almost double that of the CO2 hydrogenation process provided that the required hydrogen is sourced from water electrolysis. The hydrogenation process produces more CO2 when fossil fuel energy sources are used, but can result in more negative CO2 emissions with renewable energies. The study reveals that both of the eTL processes can outperform the conventional fossil-fuel-based methanol production process in climate impacts as long as the renewable energy sources are implemented.