Functional use of carbon dioxide for the sustainable valorization of orange peel in the pyrolysis process.

Although biomass is carbon-neutral, its use as a primary feedstock faces challenges arising from inconsistent supply chains. Therefore, it becomes crucial to explore alternatives with reliable availability. This study proposes a strategic approach for the thermochemical valorization of food processing waste, which is abundantly generated at single sites within large-scale processing plants. As a model biomass waste from the food industry, orange peel waste was particularly chosen considering its substantial consumption. To impart sustainability to the pyrolysis system, CO, a key greenhouse gas, was introduced. As such, this study highlights elucidating the functionality of CO as a reactive feedstock. Specifically, CO has the potential to react with volatile pyrolysates evolved from orange peel waste, leading to CO formation at ≥490 °C. The formation of chemical constituents, encompassing acids, ketones, furans, phenols, and aromatics, simultaneously decreased by 15.1 area% in the presence of CO. To activate the efficacy of CO at the broader temperature spectrum, supplementary measures, such as an additional heating element (700 °C) and a nickel-based catalyst (Ni/AlO), were implemented. These configurations promote thermal cracking of the volatiles and their reaction kinetics with CO, representing an opportunity for enhanced carbon utilization in the form of CO. Finally, the integrated process of CO-assisted catalytic pyrolysis and water-gas shift reaction was proposed. A potential revenue when maximizing the productivity of H was estimated as 2.62 billion USD, equivalent to 1.11 times higher than the results from the inert (N) environment. Therefore, utilizing CO in the pyrolysis system creates a promising approach for enhancing the sustainability of the thermochemical valorization platform while maximizing carbon utilization in the form of CO.