Life cycle assessment and economic analysis of carbon sequestration through biochar produced from invasive alien plants

Invasive alien plants (IAPs) are a prevalent issue in many parts of the world, negatively impacting ecosystems, biodiversity, water resources, land productivity, and substantial financial costs required for clearing and maintenance activities. However, utilising the cleared biomass to produce biochar as a soil amendment in agriculture can add value and enable carbon sequestration. Hence, this study conducted a comprehensive evaluation of various pyrolysis technologies to determine their technical and financial feasibility of producing biochar from IAPs and the carbon sequestration potential through the soil application of biochar. The production of biochar was assessed using process simulations and published experimental data for three industrial pyrolysis technologies (semi-batch retort (SBR), vertical retort (VR) and indirect retort (IR)), and compared to conventional carbon capture and storage (CCS) retrofitted to a coal-fired power station. Key findings show that the pyrolysis systems were energy self-sufficient by burning all the pyrolysis vapours, although significant energy losses occurred; the net energy efficiencies were 94.9 %, 73.8 % and 80.7 % for the SBR, VR and IR systems, respectively, while retrofitting carbon capture reduced the power plant efficiency by 10 %. For the life cycle assessment, the global warming potentials for sequestering 1 kg of carbon were 3.48 kg CO 2 eq for SBR, 3.35 kg CO 2 eq for VR, 3.41 kg CO 2 eq for IR, and 3.08 kg CO 2 eq for power station-CC. The cost of sequestering carbon was higher for coal power station with CCS (US$678/Mg CO 2 eq), compared to biochar production by IR (US$471/Mg CO 2 eq) and SBR (US$556/Mg CO 2 eq) pyrolysis technologies, while the VR pyrolysis technology had the highest cost (US$1084/Mg CO 2 eq). These findings show that soil application of biochar produced by preferred pyrolysis technologies had similar carbon sequestration benefits and lower economic costs than CCS applied at a coal power station. • Developing a carbon sequestration strategy via biochar production from IAPs. • Compared pyrolysis conversion of 3 IAPs processes to a retrofitted coal-fired plant. • The coal plant showed a 10 % drop in the net energy efficiency compared to the 3 IAPs. • The coal plant emitted less CO 2 (3.08 kg CO 2 eq) compared to the 3 IAPs process. • Although the coal plant emits less CO 2 , its sequestration cost ($678/Mg) tops 2 IAPs.