Removing the tar produced during biomass gasification is a significant challenge. Although tar reforming is a highly effective removal method, typical tar reforming catalysts are prone to coke deposition and the sintering of active metal, especially at elevated temperatures.

A recent study from the Korean University of Science and Technology has demonstrated that biochar-supported catalysts can efficiently convert biomass tar into hydrogen-rich gas at significantly lower temperatures than conventional processes. The findings could reduce the cost and energy demands of biomass gasification.

Published in the journal Biochar, the study tested biochar derived from wood chip gasification with nickel, cobalt, and iron using toluene as a representative tar compound. While nickel-based catalysts showed the strongest performance in breaking down tar compounds, introducing lanthanum as a promoter element achieved a hydrogen yield of 87% and a tar conversion rate of 93% at just 400°C.

The researchers attribute the improved performance to superior metal dispersion, higher surface basicity, and the increase in oxygen vacancies that promoted the activation, adsorption, and dissociation of H2O molecules as well as the removal of deposited coke.

Tar formation has long been a significant drawback in biomass gasification, clogging equipment, reducing system efficiency, and increasing operational costs. As such, converting the tar into useful hydrogen represents a milestone for researchers. The use of inexpensive and carbon-rich biochar increases the sustainability dimension of this approach.