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.