Characterization of the physicochemical and structural evolution of biomass particles during combined pyrolysis and CO2 gasification

The combination of pyrolysis and CO₂ gasification was studied to synergistically improve the syngas yield and biochar quality. The subsequent 60-min CO₂ gasification at 800 °C after pyrolysis increased the syngas yield from 23.4% to 40.7% while decreasing the yields of biochar and bio-oil from 27.3% to 17.1% and from 49.3% to 42.2%, respectively. The BET area of the biochar obtained by the subsequent 60-min CO₂ gasification at 800 °C was 384.5 m²/g, compared to 6.8 m²/g for the biochar obtained by the 60-min pyrolysis at 800 °C, and 1.4 m²/g for the raw biomass. The biochar obtained above 500 °C was virtually amorphous.