A study by the American Chemistry Society has concluded that mechanical recycling remains the best overall method for recycling plastics, but at lower quality than chemical recycling.
When it came to the environmental and economic impact, mechanical recycling outperformed chemical recycling due to lower energy and water use and it being a lower cost process in terms of both capital and operational costs.
However, the study found that almost all recycling processes, including chemical recycling, use less energy than creating virgin polymers.
For quality, mechanical recycling came out lower than chemical processes. This was partly because material tended to be over sorted to give a purer feedstock, but this led to greater losses of other plastics. Additionally, mechanically recycled plastic could only be used once, before needing to be downgraded to a lower quality use. While chemical recycled plastics could encompass a wider range of plastics that could be used in at least three other equivalent applications.
But the study warned that claims that chemical treatment of plastics meant infinite recycling were over-stated.
It also noted that chemical recycling can generate food-grade plastics with low contamination, but mechanical recycling required additional processes such as advanced sorting and solvent removal to meet food-grade standards.
The study can be viewed here