Scientists target PET plastic puzzle
17 Mar 2016
Researchers around the world are inching closer to halting the environmental damage caused by the polyethylene terephthalate (PET) used in plastic bottles and packaging.
Two separate research initiatives in opposite corners of the globe have taken entirely different approaches to the issue.
New processing methods for a biodegradable plastic are being explored in the US at Stanford University, while Japanese researchers have hit upon bacteria that can break down existing PET-based plastics.
The Stanford researchers are focusing their efforts on an affordable alternative to PET called polyethylene furandicarboxylate (PEF), which is made from ethylene glycol and a compound called 2-5-Furandicarboxylic acid (FDCA).
"The use of fossil-fuel feedstocks, combined with the energy required to manufacture PET, generates more than four tons of CO2 for every ton of PET that's produced," said Matthew Kanan, an assistant professor of chemistry at Stanford.
"Our goal is to replace petroleum-derived products with plastic made from CO2," he said.
As part of their research, reported in the journal Nature, they found that FDCA could be sourced from biomass, rather than petroleum, dramatically lowering the carbon footprint of the plastics industry.
Our goal is to replace petroleum-derived products with plastic made from CO2
Matthew Kanan, assistant professor of chemistry at Stanford
To reduce hazardous and energy-intensive compounds in the manufacturing process, the researchers used carbonate, combining it with CO2 and furoic acid, which is a derivative of furfural.
They then heated the mixture to about 200oC to form a molten salt.
After five hours, 89% of the molten salt mixture had been converted to FDCA, which could then be transformed into PEF plastic using relatively simple methods.
Taking a very different approach to the PET challenge, Japanese researchers from Kyoto Institute of Technology and Keio University have identified a species of Ideonella bacteria that can break it down PET.
Published in the journal Science, their discovery found the bacteria would attach to the plastic and secrete two enzymes that could jointly break down the PET.
The researchers have named the bacterium Ideonella sakainesis, but say their discovery is still in its early stages.
The breakdown process is very slow, taking six weeks at a steady temperature to fully degrade a small piece of PET film. However, researchers hope it might eventually find application in a variety of processes including industrial fermentation for recycle of waste plastic.
