(2025) Journal of Environmental Management_Carbon-negative syngas production via CO₂-assisted catalytic pyrolysis of lignocellulosic yard waste: A case study on horse chestnut shells

Lee J.; Kim M.; Lee T.; Chen W.-H.; Kwon E.E.

(Academic Press) Journal of Environmental Management ISSN: 3014797 Vol.394 Issue. Article No.127381 DOI: 10.1016/j.jenvman.2025.127381

 Yard trimmings, a major component of municipal solid waste, are abundant and carbon-neutral feedstocks used for renewable-energy production. However, their complex lignocellulosic structures limit the efficiency of energy conversion via conventional biological methods. This study presents a thermochemical strategy for syngas generation from yard trimmings. Among these, horse chestnut shells (HCSs) are one of the representative types of yard trimmings produced in large quantities worldwide from ornamental trees. Given their abundance and sustainability potential, HCSs were selected as the model biomass for this study. Lab-scale pyrolysis was conducted from 100 to 640 °C at a constant heating rate of 10 °C min⁻¹ under a CO₂ atmosphere, which enhanced the process sustainability by promoting gas-phase reactions with HCS-derived volatiles. In this setting, CO₂ acted as a mild oxidant, converting volatile biocrude components into CO and facilitating syngas production. The incorporation of a 5 wt% Ni-based catalyst accelerated these CO₂-assisted reactions, increasing the syngas yield (CO/H₂ ratio: 3.7) by 2.51-fold compared to that of conventional catalytic pyrolysis under N₂. Net CO₂ emissions were reduced to −87.55 mg g⁻¹ HCSs, indicating effective CO₂ utilisation during the process. These results establish CO₂-assisted catalytic pyrolysis as an effective method of valorizing lignocellulosic waste while contributing to CO₂ mitigation. © 2025 Elsevier Ltd

 This work was supported by a National Research Foundation of Korea (NRF) grant funded by the Korean Government (MSIT) (grant number RS-2023-NR077231 ). This work was also supported by the Basic Science Research Program through the NRF , funded by the Ministry of Education (grant number RS-2024-00412457 ).