(2026) Chemical Engineering Journal_Carbon-negative footprint in syngas production through aquatic plant pyrolysis

Kim Y.; Kim J.-H.; Lee D.; Lee M.S.; Kwon E.E.

(Elsevier B.V.) Chemical Engineering Journal ISSN: 13858947 Vol.544 Issue. Article No.178950 DOI: 10.1016/j.cej.2026.178950

In the global pursuit of carbon neutrality, biofuels have gained attention as sustainable alternatives to fossil fuels. However, the large-scale deployment of biofuel remains constrained by the insecure feedstock availability, largely due to geographical limitations and climatic sensitivity. To overcome these challenges, duckweed (DW) was chosen as a pyrolysis feedstock in this study because of its high biomass productivity, and strong environmental resilience. To further improve process sustainability, CO₂ was employed as a reactive gas medium. During DW pyrolysis, CO₂-driven gas-phase interactions (GPIs) with volatile matters (VMs) reduced the yield of oxygen- and nitrogen- containing chemical compounds in biocrude, while simultaneously increasing CO-rich syngas production. Specifically, CO₂ partially oxidizes the VMs and was reduced to CO, redirecting carbon distribution from liquid biocrude fraction toward CO-rich syngas. The partial oxidation of volatile intermediates by CO₂ also improved the structural property of the resulting DW-derived biochar, favoring its functionality for air pollutant adsorption potential. The combined application of additional thermal energy and a Ni/Al₂O₃ catalyst further intensified CO₂-driven GPIs, increasing CO-rich syngas production and establishing a favorable carbon conversion. Carbon footprint analysis demonstrated that the CO₂ mitigation achieved via syngas generation and biochar utilization exceeded the process-related CO₂ emissions associated with CO₂-assisted pyrolysis, thereby enabling the production of carbon-negative syngas. The process achieved a net CO₂ reduction of 2226.7 kt, representing 5.3 times enhancement over conventional pyrolysis. Collectively, these findings demonstrate that CO₂-assisted pyrolysis of DW represents a sustainable strategy for biomass valorization, simultaneously enhancing syngas production while achieving net-negative carbon emissions. © 2026 Elsevier B.V.

This work was supported by the Commercialization Promotion Agency for R&D Outcomes (COMPA) grant funded by the Ministry of Science and ICT (MSIT, Korea) (RS-2023-00304763) and the Korea Institute of Industrial Technology through Research and Development (UR260015).