Renewable chemicals could replace about 3 to 4 percent of the petroleum America uses by 2025.
Carpets, drapes, detergents and beverage bottles. Aspirin, vitamins, tires and automobile bumpers. These consumer products, along with athletic footgear, cosmetics, paints, inks, compact discs and cell-phone casings, start with the same raw material: petroleum.
Researchers are convinced that chemical co-products made by reacting catalysts and enzymes with cellulose and lignin from biomass might replace petrochemicals used for consumer products. The result would be more oil available for producing transportation fuel.
The National Research Council estimates that most of the petrochemicals Americans use could be displaced by renewable chemicals from biorefineries and that renewable chemicals could replace about 3 to 4 percent of the petroleum America uses by 2025. Sharon Robinson, manager of ORNL's Industrial Technologies Program, believes that the production of renewable chemicals could help the struggling U.S. chemical industry, which since 2002 has imported more chemicals than it exports, largely because of rapidly rising prices of natural gas used as a chemical feedstock and for process heat.
The primary driver for generating both ethanol and marketable chemical co-products is to make the biorefinery industry profitable and self-sustaining. Biorefineries will churn out most of their renewable chemicals by fermentation of sugars extracted from cellulose and hemicellulose. Pure cornstarch will always have a market because the feedstock is necessary for making impurity-free products, such as polymer intermediates and pharmaceuticals. A Tate & Lyle plant in nearby Loudon, Tenn., ferments cornstarch-derived glucose to 1,3-propanediol, a bio-based replacement for petroleum-derived nylon.
If bio-based chemical feedstocks are produced to replace petrochemical co-products, one concern is that the pioneer biorefineries will swamp the market for many petrochemical replacements. To address this concern, biorefineries should plan to produce co-products with other uses in large volumes. One approach would be for researchers to find ways to capture nitrogen from cellulosic feedstocks to make ammonia fertilizers and animal feed, which could have large markets and support numerous biorefineries. Switchgrass, which is 10 percent protein, is a source of nitrogen.
Some biorefineries will burn half their lignin to produce low-value process heat and “biopower” that can be used or sold to the electric grid. An ORNL team hopes to demonstrate that more valuable renewable chemicals can be produced from waste lignin. They have received internal funding to test chemical and enzymatic processes on biomass lignin purified by a technique devised at ORNL.
The researchers predict that because of lignin cleaning and advanced analytical techniques, they can demonstrate that, by using catalysts and biocatalysts to cut ether linkages, they can generate from lignin several aromatic-based compounds similar to petrochemical feedstocks used to make plastics and other high-value products. The group seeks to convince the industry that lignin can be converted into high-value chemical feed-stocks as part of a biorefinery operation.
As a result of research funded by the Departments of Energy and Agriculture, carbon fiber composites have been found to be one-fifth the weight of steel but just as strong and stiff. If they can be produced more cheaply, carbon fiber composites might replace more steel in cars, making the vehicles lighter and able to use smaller engines and less fuel. Current commercial-grade carbon fiber produced with petrochemicals costs $8 to $15 per pound—too expensive for the automotive industry. ORNL and its partners are developing technologies with an ambitious goal of making carbon fiber for under $5 a pound, a price that could lead to dramatic reductions in the cost of producing lightweight vehicles and in the amount of fuel that new cars consume.
In one of these technologies, new precursors are being developed that could be used to manufacture carbon fibers suitable for automotive composites. The precursors are made by melt-spinning a blend of purified pulp-mill lignin, a co-product of the papermaking process, and recycled plastic. Initial research suggests that lignin from biorefineries could be a similar feedstock for production of carbon fiber composites for vehicles. If the predictions prove accurate, two products from biorefineries—ethanol for automotive fuel and lignin for carbon fiber for automobile bodies—could provide a double benefit to America's environment and energy security by simultaneously reducing greenhouse gas emissions and the nation's need for imported oil.—Carolyn Krause
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