Can mixed plastics be recycled and upcycled without separation?

Abstract

With more than 400 million tonnes of plastic waste produced each year, developing effective treatment options for post-use plastics is an urgent imperative to reduce plastic pollution whilst preserving their material and chemical value within a circular economy. Whilst recycling and upcycling are emerging as important strategies to improve plastic circularity, a key bottleneck for practical adoption of these technologies is the complexity of plastic feedstock, especially from municipal streams heavily contaminated with different plastic types and non-plastic waste. This often necessitates plastic sorting and cleaning, whose complexity and labour-intensiveness add to the cost of recycling and upcycling and hinder more widespread adoption. In this review, we critically examine and spotlight the possibility of recycling or upcycling mixed plastics as an alternative to utilising only clean, single-component plastic feedstock streams. We discuss strategies to chemically recycle and upcycle mixed plastics into industrially-relevant molecules and functional materials, as well as the possibility of repurposing mixed plastics for polymer blend materials. Through this critical discussion, we hope to highlight the pressing need for designing emerging technologies for addressing the inherent heterogeneity of real-life plastic waste streams, contributing to an economically-viable and sustainable post-use plastics economy.