Comparative techno-economic and life-cycle assessment of power-to-methanol synthesis pathways

The deployment of “Power-to-Methanol” technologies by exploiting electrochemical reactions with CO2 as feedstock has received traction lately; primarily due to the continuous drop in renewable electricity price. Here, we compare techno-economic and climate benefits of three emerging “Power-to-Methanol” routes, including one-step CO2-to-methanol electrolysis; two-step synthesis, involving H2O electrolysis; and three-step synthesis, involving H2O electrolysis, and CO2-to-CO electrolysis. This study identifies key economic drivers and sets the technological goals for “Power-to-Methanol” routes to be competitive. We report that under current techno-economic conditions, none of these three emerging routes are compelling with levelized cost $860–$1585/ton methanol, which is ~2–4 times higher than the current market price ($300/ton–$500/ton). However, under future conditions (notably electricity price <3 cents/kWh), all three electrochemical routes become compelling with the levelized cost between $430–$435/ton methanol. Cradle-to-gate life-cycle-analysis reveals that electricity emission factor below <130 g CO2/kWh is required for “Power-to-Methanol” pathways to provide climate benefits over conventional route. When electricity is sourced fully from wind and nuclear power, all three routes would provide net negative emission potential of 170–195 thousand ton CO2/year. While economically all three routes seem to be equally competitive under optimistic scenario, at present only two-step synthesis is technically feasible at scale. Consequently, we establish performance targets for CO2 electrolysis under future conditions (electricity price of 3 cents/kWh), including a current density (>130 mA/cm2 (CO2-to-CH3OH), >360 mA/cm2 (CO2-to-CO)), and energy efficiency >40%, which would make one- and three-step “Power-to-Methanol” routes economically and environmentally competitive over fossil-based process in future.