Although extremely important for reducing pollution, energy consumption, and waste of natural resources, not to mention minimizing space taken up by landfills, recycling is not without its limitations and is not a complete solution. Many plastics can only be recycled a certain number of times before quality diminishes, rendering the material unusable. Only about 30 percent of plastic water bottles are currently recycled according to the Environmental Protection Agency webpage, “Facts and Figures about Materials, Waste and Recycling” (https://www.epa.gov/facts-and-figures-about-materials-waste-and-recycling). The most significant problem for recycling agencies is contamination, which happens when items that are not “clean, loose, and dry” render other nearby items also unfit for recycling. Other problems are caused by “tangler” items such as cords, hoses, and ropes, which get caught in the recycling equipment, hindering the processing of other items. As explained by Albert Bates in Transforming Plastic (mentioned above), thermosets—which make up about 8 percent of discarded plastic items—cannot be recycled, although they are often deposited in recycling bins. Recycling can be divided into primary or open-loop recycling, which occurs when the plastic will be used in the same way or form as in the original item; secondary recycling (closed-loop) is that in which the plastic will be turned into another product with a different purpose but will still consist of the same material. So-called tertiary recycling involves the chemical breakdown of the material and may involve chemical or biological processing, possibly employing microorganisms or biologically derived enzymes. Finally, quaternary recycling is that whereby energy is potentially derived from the plastic by means of incineration. A few resources on these methods are available, as detailed below.
Understanding Plastics Recycling 2E by Natalie Rudolph, Raphael Kiesel, and Chuanchom Aumnate is an accessible and informative volume covering both mechanical and chemical recycling of pre- and postconsumer waste (from packaging, building, automotive, agricultural, and electronic processes and products). These authors discuss feasible sorting and degradation methods, also analyzing the economic and international trade parameters of recycling, including comparing it with landfills and incineration, and suggest strategies to increase recycling and make it more technically and economically effective. In a more popular vein, Finn Jørgensen follows many types of plastic through the recycling process as they move back and forth between producer and consumer in his book Recycling. Materials change in value as they move along toward becoming waste. Jørgensen contends that recycling is crucial both symbolically and materially because it has the potential to foster other environmentally responsible behavior. Aimed at a more technical audience, Recent Developments in Plastic Recycling, edited by Jyotishkumar Parameswaranpillai, Sanjay Rangappa, Arpitha Rajkumar, and Suchart Siengchin, describes newer processes for plastics recycling and provides analyses of various applications, from fabrication to end-stage disposal. Some contributing authors discuss life cycle assessment of recycled plastics with particular attention the situation in developing countries.
