Framework compares closed-loop plastics recycling routes
S. Himmelstein | January 30, 2023
The ongoing expansion of technology options and routes for recycling plastics complicates the selection of the most economically and environmentally beneficial systems. Determination of optimal options may be simplified by an examination of current and emerging closed-loop polymer recycling technologies conducted by U.S. National Renewable Energy Laboratory researchers.
The study published in ACS Sustainable Chemistry & Engineering considered technical metrics such as material quality and retention, as well as environmental metrics including energy use and greenhouse gas emissions associated with closed-loop recycling of polyethylene terephthalate (PET), high-density polyethylene, low-density polyethylene and polypropylene.
Mechanical recycling is determined to outperform all other technologies in terms of economic and environmental metrics but yields lower quality plastic. Increasing the quality and quantity of plastics to be recycled through improved sorting and pretreatment could bolster the viability of mechanical recycling.
Of the chemical recycling techniques for PET, glycolysis offered the best economic and environmental performance. Organic solvents, steam and electricity were identified as key drivers of process economics, energy use, greenhouse gas emissions, land use, toxicity and water use of the recycling technologies evaluated.
The best recycled material qualities are achieved by application of dissolution, enzymatic hydrolysis and methanolysis.