Assessing environmental impacts of various solvent-dissolution routes for the pelletization of mixed plastic waste

Abstract

The vast majority of mixed plastic waste (MPW) does not degrade, thereby contributing to permanent environmental pollution. To address this, solvent-dissolution processes have been developed to recycle MPW into usable materials like blended pellets. This study evaluates five solvent-dissolution pathways, with a focus on mixed polyolefin, which constitutes about 60 % of MPW. The pathways explored include xylene, paraffin waxheptane, paraffin waxhexane, mineral oilheptane, and mineral oilhexane. Although paraffin wax and mineral oil are considered environmentally friendly, their recovery processes involve hexane or heptane, leading to higher energy use and carbon emissions. The xylene-based pathway, however, showed about four times lower energy consumption (48 MJ) and significantly reduced emissions (1.24 kg CO2 eq.) compared to fossil fuel-derived methods. In addition, mechanical property tests were conducted on the HD-PP blends which revealed a tensile modulus of 762 MPa and a tensile strength of 24 MPa, rendering them potentially advantageous for applications necessitating moderate elasticity and strength. Additionally, the study identifies dissolution and extrusion as the key stages affecting the life cycle assessment (LCA) and suggests powder production as a more cost-effective and sustainable alternative to pelletization, with lower carbon emissions. These findings offer valuable insights for improving MPW recycling through solvent-dissolution.