Comparison of pulp-mill integrated hydrogen production from gasified black liquor with stand-alone production from gasified biomass

When gasified black liquor is used for hydrogen production at a pulp mill site, significant amounts of biomass must be imported. This paper compares two alternative options for producing hydrogen from biomass: (A) pulp mill integrated hydrogen production from gasified back liquor; and (B) stand-alone production of hydrogen from gasified biomass. The comparison assumes that the same amount of biomass that is imported in alternative A is supplied to a stand-alone hydrogen production plant and that the gasified black liquor in alternative B is used in a BLGCC (Black Liquor Gasification Combined Cycle) CHP unit. The comparison is based upon equal amounts of black liquor fed to the gasifier, and identical steam and power requirements for the pulp mill. The potential for delivering low temperature excess heat to a district heating system is considered. The two systems are compared on the basis of total CO2 emission consequences, based upon different assumptions for the reference energy system that reflect different societal CO2 emissions reduction target levels. If the reference energy system includes electricity production in coal-fired power plants without CO2 sequestration and car engines that are 30% more efficient than todays , the best alternative is to use the biomass in a stand-alone hydrogen production unit. However, if electricity production has lower CO2 emissions , hydrogen produced with gasified black liquor integrated in the pulp mill can achieve the largest CO2 emissions reduction