Production of Hydrogen and Methanol via Biomass Gasification

Methanol and hydrogen are gaining increasing attention as possible future vehicle fuels. Biomass is an attractive feedstock for the production of these fuels, because its use would contribute little or no net carbon dioxide to the atmosphere when the biomass is grown renewably. Production of either fuel from biomass begins with thermochemical gasification. Partial-oxidation biomass gasifiers, such as fluidized-bed systems, are derived from coal gasifier designs. Indirectly-heated gasifiers are being developed specifically to take advantage of the unique properties of biomass relative to coal. Using process-simulation software and pinch analysis, we modeled the production of methanol and hydrogen from biomass. We investigated a variety of different gasifier designs to help illuminate the important role gasification plays in the overall efficiency of the plant. Indirectly-heated gasifier designs, such as that of the Battelle-Columbus Laboratory, give substantially better overall thermodynamic performance than partial oxidation gasifiers, such as fluidized-bed designs like that of the Institute of Gas Technology. The efficiency of producing hydrogen is higher than for methanol with either gasifier design. The total cost of producing either fuel is lowest for the indirectly-heated gasifiers. Hydrogen costs are about 20% lower than methanol costs due to the simpler equipment downstream of the gasifier and to the higher efficiency. Without considering environmental externalities, methanol and hydrogen from biomass would not be less costly than these fuels produced from natural gas at prevailing gas prices. However, the biomass-based fuels would be less costly than for coal-based production. Biomass appears to be the only renewable feedstock from which methanol can be made. Of the options for making hydrogen from renewable sources, biomass appears to be the lowest cost one at the scale considered here.