Comparative Assessment of Polystyrene Recycling Technologies through Integrated Environmental and Techno-Economic Assessment

This study presents a comprehensive Environmental-Techno-Economic Analysis (E-TEA) of six polystyrene (PS) recycling pathways, including incineration, low-pressure hydrothermal processing (LP-HTP), pyrolysis, catalytic pyrolysis, supercritical water partial oxidation (SCWPO), and polystyrene dissolution (PD). Environmental impacts were assessed using the TRACI impact categories, while economic feasibility was evaluated through process-level TEA based on experimental and literature data. LP-HTP achieved the highest climate performance, with 3.26 kg CO2 avoided per kg of PS, compared to incineration. Pyrolysis delivered the highest net present value (NPV) of $5.8/kg PS, highlighting the trade-offs between profitability and emission reduction. To explore the contribution of process energy to climate impacts, a sensitivity analysis was performed by isolating energy-related GWP and applying ±10–60% variation in energy consumption. SCWPO showed the highest sensitivity, with GWP changes up to 47%, while incineration and pyrolysis remained relatively stable (<8% change). Additionally, NPV and revenue were plotted against CO2 avoided to identify technology options that optimize both economic returns and climate benefits. The results suggest that pyrolysis and LP-HTP are the most promising candidates for sustainable scale-up, whereas SCWPO and PD face challenges due to their high energy demands or solvent usage.