From Waste to Value: Optimizing Oxidative Liquefaction of PPE and MSW for Resource Recovery

Despite widespread implementation, current waste management practices—such as landfilling and incineration—are associated with significant environmental drawbacks, including greenhouse gas emissions and resource loss. Consequently, the search for more sustainable and environmentally friendly waste valorization methods has highlighted oxidative liquefaction as a promising pathway. This study focused on two critical waste streams: personal protective equipment (PPE) and municipal solid waste (MSW). These categories were selected due to the significant increase in PPE waste generated during the recent pandemic, as well as the need to develop effective strategies to address potential future surges in such waste streams. Experiments were carried out at 200–300 °C, with waste-to-liquid ratios of 3–7% and oxidant concentrations of 30–60 wt.%. The aim was to demonstrate the potential of oxidative liquefaction as a thermochemical conversion route for resource recovery, enabling the breakdown of the organic matrix of PPE and MSW into valuable liquid products such as fine chemicals or a source of carbon in biotechnological processes. Chromatographic analyses, combined with chemometric methods, revealed how temperature, waste-to-liquid ratio, and oxidant concentration affected the yield and composition of oxygenated chemical compounds (OCCs). Using raw chromatographic data directly in optimization eliminated the need for manual gas chromatography (GC) signal processing and provided a faster approach to process evaluation. The results confirmed distinct differences in degradation behavior and OCC formation between PPE and MSW, with maximum yields of 183–212 gOCC/kg for PPE and 51–69 gOCC/kg for MSW. These findings highlight the strong influence of physicochemical waste properties on degradation and product composition. Overall, oxidative liquefaction shows significant potential as a waste-to-value strategy, supporting renewable fuels, chemical precursors, and circular economy development within the framework of biomass, biofuels, and waste valorization.