Catalytic conversion of biomass components and waste biomass for hydrogen/syngas production using biochar catalysts

Biochar produced from the pyrolysis of waste biomass (sawdust) was used as a catalyst in the two-stage, pyrolysis-catalytic steam reforming of biomass components and waste biomass in a two-stage fixed bed reactor. The thermal degradation characteristics of cellulose, hemicellulose and lignin as representative biomass components and waste biomass were determined by thermogravimetric analysis. In addition, potassium and calcium metal salts were added to a mixture of the three biomass components to investigate the effect of the alkali and alkaline earth metals on the process. The results showed that among the three main components, the pyrolysis-catalytic steam reforming of lignin produced the highest hydrogen and syngas yields in the presence of biochar catalyst. Mixing cellulose, hemicellulose and lignin produced a synergistic effect in the pyrolysis-catalytic steam reforming process, significantly promoting hydrogen release. Adding K and Ca metals to the biomass component mixture further increased the hydrogen and carbon monoxide yields. The product yield from pyrolysis-catalytic steam reforming of the waste biomass indicated that the process for real biomass is not a simple superposition of individual components, highlighting the complexity of real biomass systems. The proposed mechanism of pyrolysis catalytic steam reforming demonstrated the unique role of biochar, including its self-gasification, which significantly contributed to hydrogen and syngas production. This study not only underscores the synergistic effects in co-pyrolysis but also reveals the practical potential of biochar as a sacrificial catalyst for efficient hydrogen production.