“We have made tremendous strides over the past decade-and-a-half in reversing the psychology of industry and government on the matter of pollution prevention,” says Paul Anastas, “and yet we have barely scratched the surface of what the promise of green chemistry holds.” Indeed, beneath that surface may lie the future for whole swathes of the chemical industry, as the drive to “go green” grows more persuasive and pervasive.
As director of the Green Chemistry Institute of the American Chemical Society, Washington, D.C., and former assistant director for the environment in the White House Office of Science and Technology Policy, Anastas has been one of the champions of green technology and was one of the prime movers behind the 1997 establishment of the U.S. Environmental Protection Agency’s Presidential Green Chemistry Challenge Awards. Moving on this month to head up the new Center for Green Chemistry and Green Engineering at Yale University, New Haven, Conn., he has defined green chemistry as “the design of new products and processes that reduce or eliminate the use and generation of hazardous substances … we’re really talking about the chemistry of sustainability.”
But if pollution prevention was the original goal of green chemistry, the efforts of Anastas and researchers like him have seen the philosophy develop into one that promises as much economic as environmental benefit. The 2006 Presidential Award winners, for example, include Galen Suppes, professor of chemical engineering at the University of Missouri - Columbia, whose catalytic process for converting glycerol (glycerin) into propylene glycol could change the economics of the burgeoning biodiesel industry.
Biodiesel economics strongly depend on the market for glycerol, biodiesel’s byproduct from the transesterification of vegetable oils. The U.S. biodiesel industry is expected to introduce 1 billion pounds of additional glycerol into a market that currently only has an annual demand for 600 million pounds. So, the industry clearly needs to find a high-value use for its glycerol. Propylene glycol (PG), a less toxic alternative to ethylene glycol for antifreeze and many other uses, could be the answer. Producing it from glycerol, says Suppes, can reduce the cost of biodiesel manufacture by as much as $0.40/gal.
Suppes’ award-winning process couples a new copper-chromite catalyst with reactive distillation and offers a number of advantages, such as lower operating temperature and pressure, more efficient conversion and less byproduct, compared to previous conversion routes. The same technology also can be used to convert glycerol to acetol or hydroxyacetone, an intermediate and monomer used in the production of polyols. When made from petroleum, acetol costs around $5/lb, which limits its widespread use. However, using biomass-sourced glycerol could cut production cost to as little as $0.50/lb, opening up more markets for glycerol and so benefiting biodiesel production.
Other researchers also are investigating ways of catalytically upgrading glycerol to PG. Under the auspices of the Office of Energy Efficiency and Renewable Energy of the U.S. Department of Energy (DOE), Washington, D.C., researchers at Michigan State University, East Lansing, Mich., and the Pacific Northwest National Laboratory (PNNL), Richland, Wash., are collaborating with Archer Daniels Midland, Decatur, Ill., and UOP, Des Plaines, Ill., on the development of catalysts for an integrated process. A team led by John Holladay at PNNL has used high-throughput combinatorial techniques to screen more than 4,000 possible catalysts. (For more on developments in high-throughput methods, see R&D takes the fast track.) The next stages in the program, which runs through 2008, involve reaction evaluation and pilot scale testing and finally a conceptual design for a commercial unit.
Meanwhile, food and agricultural giant Cargill, Minneapolis, Minn., is forming a new company to make PG from renewable feedstocks using a proprietary process that is said to increase production efficiency by providing better yields and fewer byproducts than other renewable and non-renewable routes. “Cargill already sells glycerin from its biodiesel plants and has ready access through its supply chain and other sources to produce enough glycerin for world-scale production of PG,” says Jim Stoppert, Cargill’s senior director of industrial bioproducts. “We are confident that our approach to manufacturing price-competitive, renewable PG on a large commercial scale will be highly desired by the chemical industry.” Initial indications are that the product won’t require reformulation prior to downstream use. Cargill expects “market rollout to occur quickly.”
Despite the boost that such developments might give to the biodiesel industry, the biggest impact of green fuel technology will almost certainly come from bioethanol as a gasoline replacement. Current U.S. production totals around 4 billion gal/yr, mostly from corn, but there is rapidly growing interest in developing biorefineries able to process a range of feedstocks including non-foodstuff renewable biomass materials.
With biotechnology processes currently available that use enzymes to convert biomass to fermentable sugars, the U.S. could produce more than 70 billion gallons of cellulosic ethanol (as opposed to the conventional grain-derived bioethanols) per year from crop residues such as corn stover and stalks, sugar cane bagasse, wheat straw and rice straw, according to the Biotechnology Industry Organization, Washington, D.C. Jim Greenwood, the organization’s president and CEO, says 25% of the nation’s transportation fuel could be supplied from biorefineries by 2015 if development were dramatically ramped up.
It’s still very much a fledging industry but the first seeds have already taken root around the world. A demonstration plant in Ottawa, Ont., started up in 2004 by Iogen of Ottawa, provided the first pre-commercial-scale output of cellulosic ethanol. Designed to produce up to 3 million liters/yr, the plant can handle up to 40 metric tons/d of raw material feedstock such as wheat, oat and barley straw, enzymatically converting the cellulose fiber into glucose for fermentation to ethanol.