(2026) Energy Conversion and Management_Carbon negative syngas production with controlled H₂/CO ratio from fruit processing byproducts via CO₂-assisted pyrolysis

Park G.; Lee S.; Song H.; Kwon E.E.

(Elsevier Ltd) Energy Conversion and Management ISSN: 1968904 Vol.368 Issue. Article No.121980 DOI: 10.1016/j.enconman.2026.121980

The global fruit processing byproducts generation reaches approximately 500 million tons annually, and their conventional disposal methods, including landfilling, incineration, and composting raise environmental concerns. Pyrolysis has emerged as a sustainable thermochemical conversion technology that transforms fruit waste into syngas, bio-crude, and biochar. Despite the potential of bio-crude to be utilized as fuel and chemical feedstock, the complex composition of bio-crude requires post-treatment processes, limiting its economic feasibility. Therefore, further cracking of bio-crude into syngas during pyrolysis could be a more practical strategy, as syngas can be directly utilized in downstream applications. In this study, CO₂, acting as a mild oxidizing agent, was supplied as the pyrolysis atmosphere to promote syngas production. Pomegranate processing byproducts (PPB) were selected as a case study because it leaves about 50 wt% of byproducts. Single-stage pyrolysis of PPB under CO₂ atmosphere resulted in increased CO formation above 550 °C compared with N₂ atmosphere due to the homogeneous gas-phase reactions between CO₂ and volatile matters. To facilitate the effect of CO₂, a 5 wt% Ni/Al₂O₃ was employed in pyrolysis at 700 °C with catalyst-to-feedstock ratio of 1:1 (w:w). Catalytic pyrolysis under CO₂ achieved a gas yield of 51.8 wt% and produced 10.5 times more CO than single-stage pyrolysis under N₂. By adjusting the CO₂ concentration, the H₂/CO ratio for downstream syngas utilization was tunable from 0.23 to 2.03. Furthermore, the amount of CO₂ consumed during CO₂-assisted catalytic pyrolysis offset the CO₂ emitted under N₂, resulting in a net CO₂ emission reduction of 689.28 mg gPPB^-1. © 2026 Elsevier Ltd.

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government Ministry of Science and ICT (MSIT) (Grant No. RS-2023-NR077231 ).