LAUSR

Worldwide plastic production has surged over the past 50 years. In 2016, it reached 335 million tonnes per annum, with Europe alone producing 60 million tonnes. Over the next 20 years, it is expected to double. Plastic packaging is the most important product (26% of the total volume of all plastics used), although it has a short life compared to plastics used in, for example, the construction and car industries. Plastic producers and transformers are keen to highlight the benefits derived from plastic packaging; not only does it deliver direct economic profits, but it also helps prevent food waste and contamination. Further, by lessening the weight of packaging, it can reduce the fuel used in the transport of goods. This is certainly important, but even if these plastics are re-used, they inevitably become waste at some point. If we are to close the loop of the circular economy, this waste needs to be seen as a resource to be plugged back into the life cycle of plastics (PlasticsEurope, 2018). Unfortunately, a very large quantity of plastic waste leaks into the environment causing significant economic and ecological damage. For example, some 5–13 million tonnes of plastic (1.5–4% of global plastic production) end up in the ocean every year (Geyer et al., 2017). Educational campaigns are now focusing on the idea of citizens understanding themselves as members of a global community that can reduce the demand for plastic. However, according to all current expert reports, if the advantages of plastics are to be enjoyed in full, we also need to promote the most sustainable waste management alternatives, encourage recycling, use energy recovery as a complementary option and restrict the dumping in landfills of all recoverable plastic waste. Of the 25.8 million tonnes of plastic waste generated in Europe every year, under 30% is collected for recycling; 31% ends up in landfills and 39% is incinerated. Within this context, the European Strategy for Plastics in a Circular Economy, adopted on 16 January 2018, aims to transform the way plastic products are designed, produced, used and recycled in the EU. The most challenging goals laid out include those of ensuring that, by 2030, all plastic packaging in the EU should be reusable or recyclable in a cost-effective manner, and that more than half of all plastic waste generated in Europe be recycled (European Commission, 2018). Mechanical recycling is currently the most common method used to recycle plastic waste (Ragaert et al., 2017); the term covers its collection, sorting, washing and grinding. The actual procedures followed depend on the origin and composition of the waste. For example, postindustrial (PI) wastes are usually clean, have no organic residues and are of known composition. In contrast, postconsumer wastes (PC) are often mixed polymer wastes with many organic and inorganic impurities – a huge challenge for recycling. Four polymers – high-density polyethylene (HDPE), low-density polyethylene (LDPE), polypropylene (PP) and polyethylene terephthalate (PET) – dominate the plastic waste derived from PC packaging. PC is by far the biggest fraction of plastic packaging waste and the most difficult to deal with. However, some common challenges arise when mechanically recycling both PI and PC. The main issue is the fact that, under certain heat, oxidation, radiation, hydrolysis and mechanical shear conditions, polymers of both types degrade in an uncontrolled manner. Indeed, the degradation that occurs during a PC’s longterm exposure to such factors can be very significant. An additional challenge for the recycling of mixed plastic waste is the differences in the melting points and processing temperatures of the different polymers involved. Received 7 October, 2018; accepted 7 October, 2018. *For correspondence. E-mail [email protected]; Tel. +34 918373112; Fax +34 915360432. Microbial Biotechnology (2019) 12(1), 66–68 doi:10.1111/1751-7915.13328 Funding Information No funding information provided.