Carbon-negative power generation using syngas produced from CO2-cofeeding pyrolysis of lignocellulosic biomass

Abstract

Lignocellulosic biomass is typically converted into biofuels through selective conversion of saccharides in the biomass, leaving considerable amounts of lignin as waste. Pyrolysis is an alternative solution for efficient feedstock utilization; however, the fuel use of biocrude face challenges due to their compositional heterogeneity. Thus, the pyrolytic conversion of biomass into syngas could be practical for efficient combustion under manageable equivalent ratios. This study focuses on enhancing syngas production from the pyrolysis of lignocellulosic biomass, such as walnut shells (WNSs), while leveraging CO2 as a partial oxidant. During pyrolysis, CO2 reacted with WNS-derived volatile compounds, converting them into CO-rich syngas. The CO2-driven CO enhancement was observed at ≥ 520 °C, requiring measures to accelerate CO2 reaction kinetics. Therefore, operational parameters, including test temperature and CO2 composition, were scrutinized to optimize CO2 reactivity during catalytic pyrolysis. To assess industrial applicability, the resultant syngas enriched with CO was applied for power generation in a gas-turbine system. Under optimal conditions (80 vol% CO2 and 700 °C), theoretical calculations enabled to estimate 1882.5 MJ s−1 of net turbine work and 76.18 % of thermal efficiency, revealing 2.71- and 3.01-fold increases compared to reference natural gases.