(2024) Fuel_Optimizing carrot pulp waste valorization via thermochemical conversion using carbon dioxide

Kwon D.; Kim Y.; Choi D.; Tsang Y.F.; Jung S.; Kwon E.E.

This study proposes an environmentally sustainable approach for converting food waste into fuels and chemicals, especially focusing on syngas production. The carbon-negative aspect of the pyrolysis process was achieved by employing CO₂ as the reaction medium. Carrot pulp waste (CPW) was used as an exemplary food waste in this work. In the single-stage pyrolysis of CPW, the presence of CO₂ led to improved syngas generation. The introduction of CO₂, rather than N₂ carrier gas, resulted in substantial increase of CO formation at temperatures ≥ 400 °C, with a decrease in bio-oil production. This phenomenon was due to the chemical reactions between CO₂ and the volatile organic compounds (VOCs) produced during the pyrolysis of CPW. Specifically, CO₂ played a mechanistic role by providing an extra oxygen source for CO production and participating in the oxidative thermal cracking of VOCs. In-depth analysis of multi-stage pyrolysis verified the mechanistic role of CO₂, particularly at temperatures ≥ 190 °C. However, CO₂-induced reactions influenced the molecular size of the VOCs. To boost the CO₂-induced reactions for additional syngas formation, a nickel-based catalyst was introduced during the pyrolysis of CPW, which effectively expedited the homogeneous reactions initiated by CO₂, thereby indicating its potential to accelerate and optimize food waste valorization. © 2024 Elsevier Ltd

Dohee Kwon acknowledges financial support received from the Hyundai Motor Chung Mong-Koo Foundation. This work was supported by the National Research Foundation of Korea (NRF) Grants funded by the Korean Government (MSIT) (No. NRF-2023R1A2C3003011). This work was supported by the National Research Foundation of Korea (NRF) Grants funded by the Korean Government (MSIT) (No. NRF-2023R1A2C3003011).