Design and analysis of negative CO₂ emission methanol synthesis process incorporating green hydrogen and blue hydrogen

Methanol (MeOH) production by integration of green and blue hydrogen is evaluated herein. From 2018 to 2023, methanol demand increased by 3.6 % due to its use in various chemical industries as an eco-friendly fuel and as a method of transporting hydrogen and capturing renewable CO₂. Moreover, due to the continual decrease in the cost of renewable energy, research into the use of green hydrogen from electrolysis is being conducted. Most of this research has focused on producing methanol from the green hydrogen obtained from proton-exchange membrane (PEM) electrolysis along with CO₂ emissions from power plants. The present study examines processes based on oxyfuel combustion with oxygen obtained from either the PEM or an air separation unit (ASU) to produce methanol. By using oxyfuel combustion, the carbon capture process (which accounts for 30–50 % of the blue hydrogen cost) and pure (>98.75 %) 7.45 tCO₂/tH₂ can be obtained by separating H₂O from the flue gas. By using the PEM, green hydrogen can capture 0.35 tCO₂/tMeOH of external CO₂. Furthermore, a carbon techno-economic analysis (CTEA) and a sensitivity analysis are conducted to evaluate the sustainability and feasibility of the proposed processes. As a result, the levelized cost of methanol (LCOM) is $373.91/tMeOH for the Blue process and $428.78/tMeOH for the Blue + Green process, each of which is below the current market price of $500/tMeOH. If the PEM price continues to decrease, and the carbon credit increases by €300/tCO₂, after 2030, the Blue + Green process will become more lucrative than the Blue-only process. Thus, by considering the continuous decrease in renewable energy prices, the production of methanol via a hybrid Blue + Green process is suitable for a sustainable future.