Alternative sustainable routes to methanol production: Techno-economic and environmental assessment

The chemical sector is one of the largest industrial contributors in terms of CO2 direct emissions. Nowadays, methanol is produced almost exclusively from fossil fuel-based methane, thus the need of studying and developing more sustainable alternative routes is increasing importance over the years. Four different routes are considered in addition to the conventional production process of methanol from methane steam reforming: (i) Biogas Reforming-to-methanol, (ii) Biomass Steam Gasification-to-methanol, (iii) CO2 hydrogenation (alkaline water electrolysis coupled with CO2 Direct Air Capture), (iv) CO2 hydrogenation (polymer electrolyte membrane electrolysis coupled with CO2 Direct Air Capture). Based on process simulation results, techno-economic and carbon impact analyses have been performed for each process. The Biogas Reforming-to-methanol process represents the most promising alternative route from an economic point of view. A methanol selling value of 573 €/t after the application of a carbon tax demonstrated its competitiveness against the conventional production. From an emission point of view, the most performing alternatives are represented by the Biomass Steam Gasification-to-methanol with -0.88 t CO2e/t CH3OH, and the CO2 hydrogenation processes with -1.21 and -1.17 t CO2e/t CH3OH case for alkaline water and polymer electrolyte membrane electrolysis, respectively; however, such performance can be attained only if electricity from renewable energy sources is used. Conversely, such technologies are characterized by high methanol production costs (the methanol selling price should be at least 2.1 times higher than the current one).