by: Joel Makower
There’s some encouraging news for polylactic acid, the promising but beleaguered corn-based polymer intended to replace conventional petroleum-based plastics and help usher in a new era of biobased products.
Corn-based plastics have been around since the 1930s, when Wallace Carothers, a scientist for Dupont, produced a low molecular weight product by heating lactic acid under a vacuum. But they became the darlings of what some have come to call the carbohydrate economy in the 1980s when Cargill, one of world’s largest food companies, began to develop polylactic acid polymers. In 1997, Cargill formed a joint venture with Dow Chemical Co. to Cargill Dow Polymers. Together they built a large-scale $300 million PLA manufacturing facility in Blair, Nebraska, about 20 miles north of Omaha.
But sales of PLA plastics have been slow to take off. In June, Dow announced it was pulling out of the joint venture, cutting its losses at about $750 million. Cargill rechristened the company as NatureWorks, reflecting the brand name of its flagship PLA product. Sales are growing, but the plant is operating well below capacity.
The problems have been largely economic. In a world in which plastic remains largely a commodity, NatureWorks is a more costly alternative for its principal uses: for packaging material, from plastic bottles to film wrap, and for fibers used in pillows, comforters, and apparel.
Another challenge for PLA are genetically modified organisms, or GMOs. Because about 30% of the U.S. corn supply is genetically modified, some potential PLA customers -- progressive food and apparel companies, for example -- have been reluctant to have their PLA-based products tarred by the “Frankenfoods” brush. (It should be noted that no GMO corn molecules actually end up in PLA material; it dies off during the fermentation process. But many activists believe that supporting PLA means supporting conventional corn production.)
Still another challenge is that part of PLA’s promise -- its biodegradability -- has been stymied by the relative lack of composting programs in the United States.
Things have looked bleak. Environmentalists and entrepreneurs agree that if Cargill can’t make a go of bioplastics with all of its hundreds of millions invested, probably no one can, either. And if NatureWorks goes belly-up, it will be a long time before investors pony up for another bioplastics plant.
But two recent developments are encouraging. Earlier this month, DuPont and Tate & Lyle announced that they plan to open a new $100 million plant in Tennessee that uses biobased resources to make high-performance products. Scientists from the two companies have developed a new method to use corn to produce 1,3 propanediol (PDO). The resulting product, Bio-PDO, is a key ingredient in the production of DuPont Sorona, a DuPont polymer used for clothing, carpeting, plastics, and other products.
Producing Bio-PDO consumes 30-40% less energy per pound than petroleum-based PDO. Production of 100 million pounds of Bio-PDO will save the equivalent of 10 million gallons of gasoline per year, say the companies. The U.S Environmental Protection Agency presented DuPont with its annual Presidential Green Chemistry Award in 2003 for the company's research leading to the development of the Bio-PDO process.
Meanwhile, NatureWorks recently announced plans to launch a large-volume “buy-back” program in North America for post-consumer bottles made from PLA.
Through the buy-back program, commercial municipal recycling facilities in select geographic areas will separate post-consumer PLA bottles into bales, which NatureWorks will buy. The company will take them “to an appropriate end-of-life solution and/or post-consumer use based on geography of collection and prevailing market economics,” it says. PLA can be sorted from other plastics using standard near-infrared equipment.
NatureWorks says it hopes the program will help create a bridge to the development of a commercially viable post-consumer PLA market -- and that can only result in increased market acceptance for PLA itself.