Roughly 300 million metric tons of plastic waste is created every year, with nearly 12 billion metric tons of such garbage expected to pollute the planet by 2050. The molecule polyethylene, often used in packaging and grocery bags, is the largest component of plastic waste, and may take many centuries to decompose, said study senior author Susannah Scott, a chemical engineer at the University of California, Santa Barbara.
One problem with plastic is that it is cheaper and easier to produce and throw away than it is to recycle. Products made from recycled plastics often possess inferior properties to newly made ones, and breaking plastics down to their original building blocks is often complex and requires a lot of energy or chemicals, so the resulting products often do not recoup the costs of processing.
One potential way to address this economic hurdle is to “upcycle” plastic waste — to convert it into valuable chemicals. However, this often involves the energy-intensive, laborious step of breaking the plastic down to its basic components before synthesizing the desired compounds.
Now Scott and her colleagues have developed a simple, low-energy technique for converting polyethylene into alkylaromatic compounds, which are the basis of many detergents, lubricants, paints, solvents, pharmaceuticals and other industrial and consumer products and currently support a $9 billion market annually. They successfully tested their method on actual polyethylene waste consisting of a plastic bag and a water bottle cap.
“Polyethylene is one of the most used and produced plastics in the world — there is an enormous waste stream available,” said Bert Weckhuysen, a chemical engineer at Utrecht University in the Netherlands, who did not participate in this study but wrote a perspective article on the research for the journal. “They are able to turn a low-value product into a high-value product.”