Parametric analysis of ethanol-based recycling of mixed plastic waste in a circular economy

Growing concerns over the persistence and environmental impact of plastic waste highlight the need for recycling strategies that enable a circular economy by converting waste into valuable products. Despite this, integrated process models for chemical recycling of mixed plastic waste (MPW) remain limited. The novelty of this study lies in the integration of gasification of MPW to syngas, fermentation to ethanol, dehydration to ethylene, and polymerization to high-density polyethylene (HDPE) within an Aspen Plus process simulation framework, coupled with process optimization, heat integration, and energy-related GHG assessment, aiming to reduce waste and dependence on fossil resources. The framework was validated against published experimental and other data, with deviations of 0.12–4.0% across all process stages. Operating conditions were optimized through parametric analysis to maximize product yield and minimize energy consumption. Optimal gasification conditions were identified at an equivalence ratio of 0.21, steam-to-plastic ratio of 0.45, and temperature of 1000°C, producing 901.5 tonnes/day of syngas from a 500 tonnes/day plant. This syngas yielded 382 tonnes/day of ethanol, which was dehydrated at 450°C and 1 bar to produce 229 tonnes/day of ethylene. Polymerization of ethylene resulted in 228.4 tonnes/day of HDPE. The overall carbon conversion efficiency was 50.2%, corresponding to the carbon retained in HDPE relative to the carbon entering through the MPW feedstock. Heat integration reduced total heat demand by 56.1 MW (35.23%) and power consumption by 1.5 MW (6.12%), while lowering greenhouse gas emissions associated with energy consumption by 27.8% to 3.9 kg CO 2 e/kg HDPE. This approach supports scalable, energy-efficient plastic recycling and provides key insights for process design and implementation.