Technology▼Solutions Plastics from the bread basket
Courtesy of Cargill
for a company’s ideal plastic include monomerization, epoxidation with ring opening (using methanol, for In a field jump-started by skyrocketThe PSU researchers captured example), hydroformylation, ozonoling oil prices, vegetables are the new Cargill’s attention with their bioysis, transesterification, and direct plastics—but are they really green? based-polymer research, eventually oxidation. Biodegradable plastic clamshell leading to the company’s BiOH polyEach method has drawbacks and food containers and compostable ol, which substitutes soy-based polybenefits, said Zoran Petrovi´c of the utensils already fill picnic baskets, ols for up to 40% of the petroleum Kansas Polymer Research Center at and some furniture cushions conpolyol that foam manufacturers rouPSU at a recent meeting in Brazil. tain foam partially made with soytinely use to create spongy furniture Hydroformylation, for example, crebean oil. These new ates no waste byprodplastics, which rely inucts, but the technique creasingly on corn and is expensive. Ozonolysoy instead of petrosis is very efficient, but leum for their material it depends on electricfeedstocks, are often ity, which can drive up labeled as “green”. That costs. Direct oxidation tag, as well as increascan be the cheapest, ingly competitive costs reducing the already in comparison with pelower costs of using troleum-based plastics, biomaterials for plashas drawn big names tics, and it allows for such as agriculture gihigh functionality of ant Cargill and Dow the final molecules. Chemical Co. to the bioIn Cargill’s case, plastics table. the chemists chose to Last year, U.S. dohydroxylate soybean mestic production of oils with a proprietary plastic resins—used oxidation process. The Soybeans provide some of the oils for plastic feedstocks, replacing petroleum-based products that emit more greenhouse gases and take more enfor goods such as vicompany was “very ergy to produce. nyl siding for houses concerned about oxiand furniture foam— dative side products amounted to more than 113 billion stuffing. In a compacted R&D period that lead to odor; we manage those pounds (lb). About 7% of a barrel (months instead of years), the reside reactions and remove the comof crude oil (the U.S. imports apsearchers tweaked the polyol for the pounds pretty effectively,” Malsam proximately 20,000 barrels a day) bebest durability and performance unsays. comes plastic or other products. But der heat and pressure. Although being able to label its processing that petroleum to make foam green is an added benefit for plastics takes more energy than proBasic bioplastics Cargill, that is not the whole story. cessing vegetable oil, says Steve Robb, “There are different routes to the “We liked that aspect, and thought executive director of the Business same endpoint,” says Jeff Malsam, a our customers would like it, but the and Technology Institute at Pittsburg chemical engineer who leads interfundamentals are even broader than State University (PSU) in Kansas. And national business development for that,” Malsam comments. In making vegetable oils, unlike petroleum, are Cargill’s BiOH polyols. “We think our bioplastics, Cargill takes advantage a renewable resource. molecule is difficult to duplicate, but of its vertically integrated business “The thing that’s in our favor there [are] lots of ways to hydroxylstructure by shipping the vegetable [now] is the cost of the oils,” Robb ate a vegetable oil,” he says. oils the company already produces says, referring to castor and palm oil Soybean oils vary in their structo its processing plants and other in addition to soybean and others. tures and double-bond distributions; companies. New bioplastics are an “Soybean oil has remained at about about 35 different types of triacylopportunity to leverage that inthe same price for the past several glycerides and functional groups frastructure at a time when rising years, but [crude] oil has, of course, are attached at different branching petroleum costs are opening up a tripled in price.” points. Methods to create molecules market space, Malsam says.
© 2007 american chemical Society
octobEr 1, 2007 / EnvironmEntal SciEncE & tEchnology n 6639
Courtesy of Cargill
In the past 5 years, Cargill and its wholly owned subsidiary NatureWorks have both won Presidential Green Chemistry Challenge awards, a U.S. EPA partnership to recognize innovation, for their products. NatureWorks first brought its bioplastics to market in 2002 in the form of hard resins for food containers. The company continues to work out the kinks, such as modifying bioplastics that cannot hold up to microwaving. And Cargill announced in August that it would open its own R&D lab to expand the uses of its polyols.
Cargill’s soybean-based BiOH polyol, shown here, can replace 40% of petroleum-based compounds in flexible foams.
Meanwhile, the competition is growing for Cargill’s polyol. At the 11th Annual Green Chemistry and Engineering Conference in June, David Babb of Dow presented information on scaling up production of foam with a natural polyol; he projected it should be ready for market later this year. Babb reported that Dow already has produced 250,000 lb of polyol in pilot trials and is ready to scale up its manufacturing. These companies are not alone. Ford Motor Co. recently announced that it will have biobased foam in car seats in its 2008 Mustang. And smaller biotechnology companies, such as Metabolix (joined by Archer Daniels Midland) and Cereplast, have jumped into the fray, producing plastic picnic ware that biodegrades or can be broken down in large composting facilities. Researchers continue to find ways to make bioplastics perform as well as or sometimes better than petroleum-based products. Depending on how they are made, bioplastics
can be stable at higher temperatures or have more elongated fibers that prevent the foams from breaking. Despite this flurry of activity and research, biopolymers currently hold only about 2–3% of the plastics market, according to Jim Martin of the nonprofit United Soybean Board, a farmer-led advisory group that funds promotion of and research on new uses for soybeans. In 2001, the organization provided several million dollars in seed money to Cargill, Dow, and half a dozen other companies. By 2006, the companies had contributed additional research funding, bringing the total to nearly $14 million. At current rates, Martin estimates, bioplastics will make up 15% of the plastics market within a decade. But even technologically, “none of these materials are [a] 100% substitute” for petroleumbased products, he says. A 90–100% replacement rate remains the goal for researchers at PSU and elsewhere, Robb says. But in the meantime, some companies are using only a tiny bit of vegetable-based feedstocks and labeling their plastics green. “To this point, nobody has defined what constitutes green. Technically, if it’s 5% biobased, then it’s a green product,” says Robb. “One of these days, the federal government is going to come out and say it needs to have a certain percentage to be green.” Others emphasize that biobased products are not entirely green for other reasons. Some forms of soybean polyols require more toxic additives (such as isocyanate) to make them strong enough to compete with typical petroleum plastics, researchers report. And a few companies, including Cereplast, are using nanoparticles to stabilize their biobased materials, notes Brenda Platt of the Institute for Local Self-Reliance, a nonprofit organization that promotes “zero waste”. “That’s letting the genie out of the bottle,” says Platt, because researchers still haven’t pinned down nanoparticles’ environmental and human health effects. “Just because it’s biobased, is it more sustainable? The answer is no,” says Mark Rossi of Clean Production Action, a nonprofit group that promotes green chemistry. Eco-friendly purveyors, such as the organic grocer Whole Foods Market, household-
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products maker Seventh Generation, and clothing manufacturer Patagonia, have “been really reluctant to accept PLA [polylactic acid plastics] as sustainable,” Rossi says, because of concerns about agricultural pesticides, genetically modified organisms, and other practices related to soybean and corn production. Still, the “whole biobased question in general” presents a “real opportunity to make much greener materials, cradle to cradle.”
Keeping it green Less energy is required to produce soybean polyols and other vegetable-oil-based plastics than petro-products, Robb says. Cargill’s preliminary life-cycle analyses show its BiOH polyols produce 36% less greenhouse gas emissions and reduce total energy demand by 23% when replacing petroleum versions. According to calculations by a consulting firm hired by Cargill, 1 million lb of BiOH polyol saves about 2200 barrels of crude oil (nearly 700,000 lb). Add to this that soybeans and other crops are renewable resources, and “you don’t have to worry about running out” of them, Robb notes, with cropland still available for growing plastic feedstocks. Jupiterimages
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From oil refineries to biorefineries: could soybean and other vegetable oils displace petroleum in plastics?
Martin believes that biobased components will bring the U.S., which now imports petroleumbased chemicals at high rates, back to self-reliance from “chemical dependence.” Their use may also result in a return to historic products such as linoleum, the canvas and linseed oil product that graced 1920s kitchen floors, while scientists pursue new avenues for creating biobased plastics. —NAOMI LUBICK
