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

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 wax heptane, paraffin wax hexane, mineral oil heptane, and mineral oil hexane. 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. ● Assess solvent-dissolution routes for plastic waste recycling. ● Identify xylene as the eco-friendliest solvent with lower carbon emissions and energy use than paraffin wax or mineral oil ● Show reduced carbon footprints and energy use compared to virgin plastics, especially in marine eutrophication and oxidation. ● Advocate powder over pellets, emphasizing extrusion and dissolution variables to lower environmental impacts. ● Uncertainties in full-scale use and regional outcomes remain, urging further research for sustainable waste management.