208 views | Akanimo Sampson | April 26, 2021
Burdened by the growing concern around the world about the accumulation of plastic waste in landfills, researchers are currently looking for less expensive and more environmentally sustainable alternatives.
One of the problems with the available plastics is that they can only be recycled mechanically – plastic waste is melted down, while preserving its molecular structure.
This process is called “down-cycling” because the resultant material is inferior and has less applicability than the initial product.
Lead author of a new study on infinitely recyclable plastics from Lawrence Berkeley National Laboratory, Nemi Vora, said “with mechanical recycling, what we are doing is just delaying the waste ending up in landfill. If it doesn’t end up in landfill today, it is going to end up in landfill five to six years down the line.”
Another way of making plastic available for reuse is chemical recycling, whereby its molecular bonds are severed, making it possible to reform the material back into “pristine” plastic. The problem with this method, however, is that it requires enormous amounts of energy.
To overcome this problem, Vora and her colleagues have developed a new material called polydiketoenamines (PDKs) which has special bonds that can be broken down with strong acid at room temperature, opening the door to infinite recycling.
The estimated cost of recycling the new material is around $1.50 per kilogram, which is comparable to three other types of commonly used plastics.
Producing virgin PDK resin, on the other hand, would cost roughly $45 per kilogram – way too much for commercial use.
Given that a single compound called N,N’-dicyclohexylcarbodiimide (DCC) accounts for nearly 50% of the production cost and much of its associated greenhouse gas emissions, the research team is now working on reducing its use in the production of PDKs.
According to the study’s senior author, Corinne Scown, also from Berkeley, PDKs could be great for products that don’t stay in circulation for very long and make it possible to recover most of their constituent parts, such as electronics, shoes, and sunglasses. Some other products will, unfortunately, require different solutions.
“We need to invest in novel ways of recycling the plastics that we have because they’re already so integral to our society”, Scown said. “In other cases, maybe you want to go the route of increasing the use of compostable plastics.”