Controlling the compositional matrix of pyrogenic products using carbon dioxide in the pyrolysis of agricultural plastic waste

Plastics are extensively employed in agriculture, generating an enormous volume of plastic waste. This study investigated the pyrolysis of silage film waste (SFW) to enable its conversion into energy/value-added chemicals. CO_₂ was chosen as the reactive medium to provide green pyrolysis. Nevertheless, the results showed that most of the carbon in the SFW was assigned to wax-like oil formed by thermal cracking. It was presumed that the reactivity of CO_₂ was effective only under certain optimal temperature conditions. To this end, the test setup was modified to increase the residence time of the reactants (CO_₂ and volatiles from SFW). With respect to inert gas conditions, syngas formation was observed under CO_₂ conditions. The enhanced formation of syngas was realised by the simultaneous reduction of CO_₂ into CO and the oxidation of volatiles into CO. CO_₂ also enhances the thermal cracking of volatiles, leading to enhanced formation of C_₂-hydrocarbons. These features provide an effective means of decreasing the aromaticity of oil from SFW pyrolysis. The simultaneous reduction of CO_₂ into CO and oxidation of volatiles into CO block the mechanistic pathway to form polycyclic aromatic hydrocarbons. CO enhancement by CO_₂ offers an effective means for abating the fate of toxic chemicals. Copyright © 2024 Elsevier B.V. All rights reserved.