Scientists, including one of Indian origin, have discovered a new way to make plastic from carbon dioxide and plant materials such as agricultural waste and grasses, that may dramatically lower the carbon footprints of the plastics industry.
The new technology could provide a low-carbon alternative to plastic bottles and other items currently made from petroleum, researchers said.
"Our goal is to replace petroleum-derived products with plastic made from carbon dioxide (CO2)," said Matthew Kanan, an assistant professor at Stanford University.
"If you could do that without using a lot of non-renewable energy, you could dramatically lower the carbon footprint of the plastics industry," said Kanan.
Many plastic products are made from a polymer called polyethylene terephthalate (PET), also known as polyester.
Worldwide, about 50 million tonnes of PET are produced each year for items such as fabrics, electronics, recyclable beverage containers and personal-care products.
PET is 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 said.
Researchers, including graduate student Aanindeeta Banerjee, focused on an 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 said.
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 and sustainable way to produce FDCA.
One approach is to convert fructose from corn syrup into FDCA. But growing crops for industry requires lots of land, energy, fertiliser and water.
"It would be much better to make FDCA from inedible biomass, like grasses or waste material left over after harvest," Kanan said.
The researchers have 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.
But making FDCA from furfural and CO2 typically requires hazardous chemicals that are expensive and energy-intensive to make. Researchers solved the problem by using carbonate.
They combined carbonate with CO2 and furoic acid, a derivative of furfural and heated the mixture to about 200 degrees Celsius to form a molten salt.
After five hours, 89 per cent of the molten-salt mixture had been converted to FDCA, researchers said.
The next step, transforming FDCA into PEF plastic, is a straightforward process, Kanan said.
The study was published in the journal Nature.
