TECHNOLOGY
Explaining chemical recycling processes
Chemical recycling is an umbrella term that includes a variety of technologies, each with their own process characteristics, input requirements and outputs. We explain the technologies
Few in the plastics industry will not have heard of chemical recycling but that simple term covers a huge range of quite different technologies. Today’s chemical recycling technologies can be classified into three broad concepts: dissolution, depolymeri- sation, and thermal cracking. These three ap- proaches differ, at a conceptual level at least, in the type of materials they can handle, the amount of “chemistry” involved, and the product that results. Dissolution technologies use carefully selected solvents to dissolve the polymer from the mixed waste, allowing insoluble contaminants such as fillers and pigments to be filtered out. The dis- solved polymer can then be precipitated and recovered from the solvent, which is reused. This is a physical process — the chemical composition and structure of the polymer is unchanged. As a result, many of its proponents consider it to be closer to
Chemical Recycling – Global Insight 2022
mechanical than chemical recycling and promote it accordingly, using terms such as solvent-based purification or physical or material recycling. The key to success in dissolution is the selection
of a solvent that recovers only the target polymer. This means it is best suited for use with relatively homogenous waste streams. A number of pilot projects are already well advanced — Purecycle Technologies in the US, for instance, is targeting polypropylene with a technology licensed from P&G while Canada’s Polystyvert is focusing its efforts on polystyrene. The need for a relatively homogenous waste
stream does not necessarily mean that dissolution technologies are suitable only for mono-material plastic waste. Germany’s APK, for example, is developing its technology to recover LDPE and PA from multi-layer films.
Main image: Some chemical recycling involves changes in chemistry, but not in the case of dissolution
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IMAGE: SHUTTERSTOCK
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