Renewable Methanol Production from Polyolefin Waste Via Pyrolysis: Process Simulation and GHG Emissions Evaluation

This study presents an integrated process for the valorization of plastic solid waste using a thermal pyrolysis stage followed by a steam reforming system, focusing on energy recovery and methanol production. The first pyrolysis reactor operated at 500°C, while the second reactor temperature was set at 800°C, achieving a gas yield of 98%. The gas composition profile exhibited a favorable (H2 - CO)/(CO + CO2) ratio of 2.06 for plastic waste, further enhancing methanol production. The data from these experimental campaigns was used to model the reaction section using Unisim Design® software. A comprehensive process scheme was developed, incorporating compressors to achieve 70 bar and 220°C, the required conditions to optimize methanol synthesis in a plug flow reactor with an integrated purification unit. This setup was simulated to ensure optimal thermal integration for efficient methanol production from syngas. The environmental impact of the process was assessed by evaluating plant emissions across a short supply chain, following the criteria set out in Annex I of the Renewable Energy Directive (RED III). The assessment focused on determining whether the methanol obtained from recycled carbon could be classified as renewable, based on achieving emission savings of more than 70% compared to conventional fossil fuel production and usage. The results underscore the feasibility of producing renewable fuels (i.e. methanol) from plastic waste, highlighting the vital role of closed-loop recycling in reducing carbon emissions and improving the sustainability of polyolefin production.