Circular Economy of Expanded Polystyrene Waste: Techno-Economic and Life Cycle Assessments of Chemical Recycling Processes
24 Pages Posted: 26 Dec 2023
Abstract
The global issue of plastic waste demands urgent attention due to its potential to harm the Earth’s ecosystem. Chemical recycling of plastic waste offers a fresh perspective that aligns with the principles of the circular economy and the pursuit of carbon neutrality, particularly because plastic waste can be utilized as a carbon source to replace fossil-based feedstock. In this work, techno-economic and life cycle assessments were conducted based on an experimental study to demonstrate the chemical recycling of expanded polystyrene (EPS) waste through depolymerization, producing recycled styrene monomer (r-SM). The chemical recycling process were simulated in a commercial process simulator to obtain mass and energy balance and equipment sizing. The outcomes of it serve as inputs for economic and life cycle assessments. Three cases were evaluated based on pre-conditioning and product purity: Case 1) low-grade r-SM (> 95% purity) without solvent, Case 2) low-grade r-SM (> 95% purity) using THF as a solvent, and Case 3) a high-grade r-SM (> 99% purity) without solvent. Economic analysis results indicate that Case 3 offers the most economically viable option, with a minimum product selling price (MPSP) of $1.06/kg, and its quality is compatible with virgin styrene monomer (v-SM). Sensitivity analysis identifies EPS waste cost as the primary MPSP influencer. Life cycle assessment (LCA) results reveal that all cases have a lower Global Warming Potential (GWP) result compared to the production of v-SM, with Case 1 being the most environmentally friendly option, achieving an 89% GWP reduction. Energy consumption is identified as the primary factor contributing to GWP results. These findings reveal further research prospects to explore in the pursuit of implementing EPS waste recycling.
Keywords: plastic recycling, Circular economy, Process design, techno-economic analysis, life cycle assessment, depolymerization
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