All Ears

Dec. 21, 2004
Corn and microorganisms are the kernels of new environmentally friendly polymers.

In The Graduate, one of young Ben's neighbors buttonholes him and delivers the classic line: "I just want to say one word to you. Plastics." If the movie were shot today, that word might be "corn." A new era is dawning in materials science, one characterized by the convergence of agriculture, biotechnology, and traditional chemistry where farmed crops are converted into chemical intermediates, and ultimately polymers and plastics, with the help of microorganisms. These new materials are less expensive to manufacture than traditionally manufactured products, create less waste and pollution, and offer some performance advantages. The raw materials are completely renewable and include corn, wheat, rice, and sugar beets. And the microorganisms have the ability to be genetically programmed to create new, even exotic materials. The first to reap benefits from the polymer harvest include Cargill Dow Polymers LLC, Minnetonka, Minn., a joint venture formed specifically to glean new plastics out of plants, and Du Pont & Co., Wilmington, Del. Both have announced substantial new capacity. Cargill Dow, for instance, will be on stream with a new plant for 140,000 metric tons of its NatureWorks polymers by next year. Extracting dextrose from 40,000 bushels of corn per day, the plant will have its entire production sold out by the time the facility is up and running, according to the company, which plans 1 billion pounds capacity worldwide by 2006. "A tremendous opportunity to revolutionize the polymer industry," says Warren Staley, president and CEO of Cargill Inc., Minneapolis, when asked about the potential of the Cargill/Dow joint venture and materials based on renewable resources. Du Pont will be on-stream in 2003 with its Sorona line of polymers based on corn and the action of microorganisms, but that could be just the beginning. "We have established a goal of deriving 25% of our revenues in 2010 from areas other than those requiring depleting raw materials," said Du Pont chairman and CEO Charles O. Holliday Jr. in a September 1999 address to the Boston Chief Executives Club. By comparison, in 1998 less than 5% of Du Pont revenues came from renewable feedstocks, and all energy was derived from conventional sources. Sugars to polymers How does it work? While most plastic materials start as some kind of petrochemical feedstock, the raw materials for these new polymers are the carbohydrates (sugars) in certain plant materials. Once extracted, the sugars are acted on by microorganisms to yield chemical entities that can be polymerized into materials that will compete head-to-head with plastics such as polyesters and nylon. The action of the microorganisms is akin to the fermentation that occurs when grapes are converted into wine. Cargill Dow uses a cousin of lactobacillus, the bacteria used to create yogurt from milk, to form lactic acid, which is the basis for NatureWorks polylactide materials. Du Pont will use a microorganism genetically engineered by Genencor International Inc., Palo Alto, Calif., to create 1,3-propanediol, the starting material for the Sorona-brand family of polymers. The ability to genetically alter microorganisms and their metabolic products heralds a bright future for these polymers. "I think it's the beginning of a new era," says Pat Gruber, executive vice president, technology, Cargill Dow. "In the past we have relied on simple fermentation techniques. Now we will start to manipulate the organisms with biotechnology, as Du Pont has done. With that capability, there is a whole new variety of materials that could be made. We see a multibillion-dollar business potential just for us. So you are talking in the tens of billions of dollars for an industry in a 10- to 15-year time frame." In related work based on genetic manipulation, Du Pont reports investigation of growing new materials in plants themselves. "We may one day be able to create a biosilk that grows in plants," says Holliday. "We are also looking for the genes that control the synthesis of natural rubber that would enable us to use plants commonly grown in this country as a source of this material." Lean, clean, and green In addition to providing new-product opportunities, the industry sprouting from the combination of renewable resources and microorganisms will be easy on the environment and the pocketbook. For example, throughout the entire value chain the creation of NatureWorks polymers uses 30% to 50% less fossil fuel, according to Cargill Dow, and releases less carbon dioxide into the atmosphere. In fact, as corn grows it takes carbon dioxide out of the atmosphere. The biotech end of the processes is water based. Finished products are eminently recyclable and can be composted. "They also offer substantial reduction in capital manufacturing costs, which can result in less expensive products," says Kevin Swift, senior director, policy, economics, and risk analysis, American Chemistry Council (formerly the American Chemical Manufacturers Assn.), Washington. Manufacturing processes "are more flexible, with lower break-even points, and can be operated at a lower scale, sometimes one-tenth the size of a large polyethylene plant." In traditional chemistry, high pressure and high heat are used in the conversion of petrochemicals to finished plastics. The biotech routes require much less of both. "It's sort of the equivalent of cold-water washing of clothes, to take a household example," says Swift. In the marketplace these new polymers likely will first find a home as fibers in apparel, upholstery, and carpeting (fiber and backing), and as film in packaging applications. In clothing, they offer wrinkle resistance, softness of touch, and stretch recovery, and are easier to dye than current synthetics. In blends with cotton, for instance, they offer the comfort benefits of natural fibers, with synthetic fibers' ability to wick away moisture. In packaging applications, the Cargill Dow polymers in particular offer high clarity, stiffness, and sealability. Excellent twist retention and an ability to hold sharp creases portend uses in unusual packaging applications. In combinations with cardboard, the materials can be composted after use.

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