New Sources for Old Plastics
Marc A. Hillmyer, Director, Center for Sustainable Polymers, hillmyer@umn.edu
Most of us take advantage of polymer technology everyday, usually before arriving at work. We drive on rubber tires that grip the road on icy days, have a grapefruit juice out of a plastic bottle that keeps this delicious breakfast beverage fresh, and free our shoes of dirt and snow by stomping on our office carpet (no worries, the polymer fibers in this floor covering are easy to clean). However, the use of these products continually depletes our petrochemical resources and adds to greenhouse gas emissions.
These plastics don't grow on trees...or do they? There has been a recent push by the polymer industry to move toward sustainable sources for the "old polymers" we know and love to use. The building blocks for polymers have traditionally come from petroleum and natural gas. Compounds like ethylene, ethylene glycol & terephthalic acid, and isoprene are used to create polyethylene (PE) which is heavily used in many consumer products like plastic bags and packaging, polyethylene terephthalate (PETE) used in numerous bottling applications, and polyisoprene (PI) which is the base of many of our (synthetic) rubber products. Now, companies like Genencor and Goodyear are developing routes to isoprene using a fermentation process, Braskem plans on converting ethanol from renewable feedstocks like sugarcane into ethylene, and Coca-Cola just announced that their Dasani brand water will soon be contained in PETE bottles that contain "up to 30% biobased content" which will be achieved by using molasses as a feedstock for the ethylene glycol component. According to Chemical Engineering News (the weekly magazine published by the American Chemical Society), Michael Schluthesis, the director of sustainable packaging design at Coca-Cola, said "Our goal would be to end up with the same molecule at the end of the day."
Introducing new biorenewable polymers in the market place comes with its challenges. But it is exciting that the old stalwarts of the polymer industry are now being derived from biorenewable feedstocks. One of the major factors in the adoption of sustainable materials is their cost. Will these bio-derived chemicals be as cheap (or cheaper) than the petrochemically-sourced ones? We'll see. This will depend on advances in technology optimization of these newly developed routes, the price and availability of fermentable biomass, and, of course, the price of oil. Policy can also have a large impact on the previously mentioned factors. At the Center for Sustainable Polymers we plan to work with our colleagues at the Humphrey to help inform the public and political leaders of the potential benefits that bio-based polymers can have on the environment and the stability of essential consumer goods.
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