Nov. 20, 2021
What would modern life be without plastic? According to the World Economic Forum, plastic production has exploded over the past half century, so where has all that plastic gone?
Most of it ends up in landfills, where it can take up to 500 years to break down and can leak contaminants into the soil and water. An estimated 165 million tons of plastic waste is already floating in the ocean, threatening the health and safety of marine life. This includes microplastics, tiny particles less than 5 millimeters long from cosmetics, fabrics or larger debris that can be ingested by marine wildlife.
We recycle relatively little plastic litter because there are many different types of plastics with different chemical compositions, and recycled plastics can be contaminated by a mix of types. Plastic waste is also contaminated by materials such as paper and ink. Separating plastics from other recyclables and different types of plastics from each other is a labor-intensive task for which there has been no simple solution to date.
Although the Plastics Industry Association has developed seven codes to distinguish between types of recycled plastics, only polyethylene terephthalate (PET, used in synthetic fibers and water bottles) and high-density polyethylene (HDPE, used in water bottles, bottle caps, and water pipes) are actually recycled on a regular basis. But in a growing number of cities, such as New York and Chicago, low-density polyethylene (LDPE) plastic bags are now also being recycled. And the recycling industry is increasingly using near-infrared spectroscopy, which can identify the chemical composition of plastics, to improve the efficiency and speed of recycling.
Recyclable plastics are first sorted, shredded and stripped of impurities such as paper. The pieces are then melted and formed into pellets that can be made into other products.
Plastics are made from oil or natural gas in a chemical process that combines smaller molecules into one large chain-like molecule, often with other substances added to give it special qualities. It is estimated that plastics production uses 4% of global oil production . Because these polymers contain energy from fossil fuels (and actually have a higher energy value than coal and wood), leaving so much of it in landfills not only harms the environment, but is a huge waste of a valuable resource.
There are three ways that non-recycled plastics can be used for energy production: by converting them directly into liquid fuels, by using separated plastics as fuel in special types of power plants, and by increasing the amount of waste burned in waste-to-energy facilities.
Burning more waste in a waste-to-energy facility will recover the energy inherent in plastics and reduce greenhouse gas emissions because landfills emit methane (a greenhouse gas 20 times more potent than carbon dioxide) when waste decomposes. Unlike incinerators of the past, modern waste-to-energy facilities generate electricity and heat in boilers designed for complete combustion. They produce electricity that has less of an environmental impact than almost any other source of electricity.
The United Nations Environment Programme report describes the production of gaseous fuels, using pyrolysis of plastic waste, and solid fuels derived from a mixture of waste plastics, paper and wood. The material is first shredded, sorted, and then made into pellets.
The best solution to the plastics problem remains to reduce the use of plastics and to reuse and recycle them whenever possible. More policies that ban plastic bags, require bottle deposits and expand recycling would help. But millions of tons of plastic waste remain in landfills across the country; technologies that can harness this waste as a resource can provide multiple benefits, helping to clean up the environment, reduce our use of non-renewable virgin resources, reduce greenhouse gas emissions and generate energy.