Recent advances in organic waste pyrolysis and gasification in a CO₂ environment to value-added products

The persistent combustion of fossil fuels has resulted in a widespread greenhouse effect attributable to the continual elevation of carbon dioxide (CO₂) levels in the atmosphere. Recent research indicates that utilizing CO₂ as a pyrolysis gasification medium diminishes CO₂ emissions and concurrently augments the value of the resultant pyrolysis gasification products. This paper reviews recent advancements in the pyrolysis gasification of organic solid wastes under a CO₂ atmosphere. Meanwhile, the mechanisms of CO₂ influence in the pyrolysis and gasification processes were also discussed. In comparison to noble gases, CO₂ exhibits reactivity with char at≥710 °C, resulting in additional mass loss of the sample. In addition, CO₂ was able to increase the specific surface area and stability of biochar and reduce biooil toxicity by lowering the content of cyclic compounds in the biooil, while CO₂ was able to react with GPRs with some volatile products (e.g., light hydrocarbons) to increase biogas yield. Finally, CO₂ also prevents catalyst deactivation by reducing secondary coke formation. We also recommend directing future attention toward utilizing unpurified CO₂ in pyrolysis and gasification. This review aims to expand the utilization of CO₂ and advocate for applying pyrolysis gasification products.