Did you know that a whopping 380 million tons of plastic are created worldwide each year? Worse yet, as the plastics market continues to increase, many analysts are predicting that plastic production could quadruple by 2050. The trouble with all this plastic production is that more than 75 percent of plastics are discarded after one use—and many of them end up in our oceans and waterways, where they harm wildlife and spread pollution.
Plastics can be melted and reprocessed, of course, and this is what recyclers have been doing for decades. However, this type of recycling yields lower-value materials that are not as structurally strong as the original, so it’s essentially a form of downcycling—for example, turning plastic bottles into molded park benches.
The reason plastics don’t degrade when left in the wild or in landfills is because they have very strong carbon-carbon bonds that cause them to break up into smaller plastics known as microplastics.
These strong bonds can be hard to break to create new and high-value plastics, but researchers at Northwestern University, Argonne National Laboratory, and Ames Laboratory came together to do just that.
“Our team is delighted to have discovered this new technology that will help us get ahead of the mounting issue of plastic waste accumulation,” said Northwestern’s Kenneth R. Poeppelmeier, who contributed to the research. “Our findings have broad implications for developing a future in which we can continue to benefit from plastic materials, but do so in a way that is sustainable and less harmful to the environment and potentially human health.”
The researchers decided to take on upcycling plastic by recouping the high energy that holds carbon-carbon bonds together through a catalytic process that converts single-use polyethylene molecules into value-added commercial products.
The catalyst the research team used consists of platinum nanoparticles deposited onto perovskite nanocubes. They chose perovskite because it is stable under high temperatures and pressures and a very good material for energy conversion.
What they found was that under moderate pressure and temperature, the catalyst was able to break plastic’s carbon-carbon bond to produce high-quality liquid hydrocarbons that could be used in motor oil, lubricants, or waxes, a first step in upcycling plastic. These hydrocarbons could also be further processed to make ingredients for detergents and cosmetics.
The catalytic method produced far less waste than recycling methods that melt plastic or use conventional catalysts, which generate greenhouse gases and toxic by-products.
It’s hard to tell yet whether this method of upcycling plastic will be commercially viable and cost-effective, but it’s definitely a step in the right direction.