Production of carbon-negative syngas through CO2-driven thermochemical conversion of acacia sawdust

Abstract

This paper proposes a strategic approach for producing carbon-negative syngas through the thermochemical conversion of biomass using acacia sawdust as a model compound. CO₂ was employed as the reactive medium during the pyrolysis of acacia sawdust to increase the conversion of carbon in biocrude into syngas. In the single-stage pyrolysis, more production of CO under CO₂ than N₂ condition was observed above 580 ˚C. This observation demonstrated that the reaction in gaseous medium between the CO₂ and volatile matter released from the thermolysis of acacia sawdust did occur. However, the kinetics of the reaction in gaseous medium driven by CO₂ were slow. As such, a Ni-based catalyst was introduced to promote the kinetics of reaction in gaseous medium driven by CO₂. Introducing CO₂ in the catalytic pyrolysis further increased the yield of syngas, reaching 22.8 mmol g_sample^-1, which was higher than that under N₂ conditions (18.6 mmol g_sample^-1). The proposed process (CO₂-driven catalytic pyrolysis of acacia sawdust) achieved a net CO₂ emission of −151.0 mg g_sample^-1. All the experimental findings show that the CO₂-drvien catalytic pyrolysis system may serve as an effective strategy for carbon-negative syngas production, contributing to greenhouse gas (CO₂) mitigation.