Hybridization of the thermo-chemical process of polyvinyl chloride in the production of bioethanol using horse hay

The improper disposal of polyvinyl chloride (PVC) is hazardous to the environment. To rectify the inappropriate disposal of PVC, this study proposes a sustainable method to valorize hydrogen chloride (HCl) (from the thermolysis of PVC) in bioethanol (BE) production. Prior to saccharification, lignocellulosic biomass (horse hay) was treated with HCl. The optimized parameters for acid treatment were determined from a series of saccharification tests. In detail, the sugar recovery yield was 75 % after 2 % HCl, 120 °C, and 2 h treatment of horse hay. In addition, this study suggests that a nitrogen source is required during fermentation to enhance BE productivity. To valorize the residual materials from the saccharification of horse hay and dechlorination of PVC, they were pyrolyzed. Co-pyrolysis of the residues was performed in a CO₂ gas environment. The gas-phase reaction of CO₂ and volatiles stemming from the two residues was observed, which directly led to the enhanced generation of carbon monoxide (CO). These observations are attributed to the simultaneous redox mechanisms of CO₂ and volatiles. To accelerate the reaction rate of the redox mechanisms, catalytic co-pyrolysis of the residues over Co/SiO₂ was performed, and such attempts were confirmed by the enhanced formation of H₂ and CO. This study highlights that the hybridization of the thermochemical process of PVC in the production of BE could be a viable approach for waste valorization.