Scientists from Stanford University in the US have discovered a novel way to make plastic from carbon dioxide and inedible plant material such as agricultural waste and grasses.

Researchers say the new technology could provide a low-carbon alternative to plastic bottles and other items currently made from petroleum.

“Our goal is to replace petroleum-derived products with plastic made from CO2,” says Matthew Kanan, an assistant professor of chemistry at Stanford. “If you could do that without using a lot of non-renewable energy, you could dramatically lower the carbon footprint of the plastics industry.”

Kanan and his Stanford colleagues described their results in the March 9 online edition of the journal Nature.

Changing the plastic formula

Many plastic products today are made from a polymer called polyethylene terephthalate (PET), also known as polyester. Worldwide, about 50 million tons of PET are produced each year for items such as fabrics, electronics, recyclable beverage containers and personal-care products.

PET is made from two components, terephthalic acid and ethylene glycol, which are derived from refined petroleum and natural gas. Manufacturing PET produces significant amounts of CO2, a greenhouse gas that contributes to global warming.

“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,” Kanan says.

Introducing PEF

For the Nature study, he and his co-workers focused on a promising alternative to PET called polyethylene furandicarboxylate (PEF). PEF is made from ethylene glycol and a compound called 2-5-Furandicarboxylic acid (FDCA).

“PEF is an attractive replacement for PET, because FDCA can be sourced from biomass instead of petroleum,” Kanan says. “PEF is also superior to PET at sealing out oxygen, which is useful for bottling applications.”

Despite the many desirable attributes of PEF, the plastics industry has yet to find a low-cost way to manufacture it at scale. The bottleneck has been figuring out a commercially viable way to produce FDCA sustainably.

Overcoming challenges

The Stanford team has been experimenting with furfural, a compound made from agricultural waste that has been widely used for decades. About 400 000 tons are produced annually for use in resins, solvents and other products.

Graduate student Aanindeeta Banerjee, lead author of the Nature study, combined carbonate with CO2 and furoic acid, a derivative of furfural. She then heated the mixture to about 290 °F (200 °C) to form a molten salt.

The results were dramatic. After five hours, 89% of the molten-salt mixture had been converted to FDCA. The next step, transforming FDCA into PEF plastic, is a straightforward process that has been worked out by other researchers, Kanan notes.

Standford University (News Wise)