Designed to degrade.

sciencemag.org SCIENCE to access higher-purity polymer feedstocks will be required to minimize the dependence on consumer separation of materials manually during disposal for collection. Strategies for recycling mixed or contaminated feedstocks are also needed. Current compatibilizers must be customized for a given waste composition, which is not going to be practical on the large scale. More versatile methods are needed for controlling the physical behavior of plastic waste mixtures, which are diverse and variable in composition. Of similar importance is the ability to recycle composites containing more than one type of material (typically polymers, metals, or ceramics). Low-energy separations of mixed materials such as composites and multilayer packaging will require further development; there is currently no effective way to achieve such separation mechanically. Successful adoption of new recycling approaches will require cooperation among researchers, industry, and government. New practices are already beginning to find their way into cities. For example, startup companies are scaling up chemical recycling methods for polystyrene waste and developing sorting processes for separation of materials into pure feedstocks. Such efforts are enhanced by programs to educate the public on the benefits of recycling. Furthermore, advanced computational modeling and data analytics for new catalyst, compatibilizer, and polymer discovery (with the ultimate goal of developing predictive capabilities) will aid in the optimization of recycling processes. Such efforts raise hope that before long, recycling rates for plastics will be much higher than today. j