Chemical industry sees green

Developments target economics, not just environmental benefits. While pollution prevention was the original goal of green chemistry, today’s efforts promise to have a substantial economic impact.

By Mike Spear, editor at large

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The first true commercial-scale plant, however, was scheduled for start-up in December in Babilfuente, Spain, at the BCyl cereal ethanol plant of Abengoa Bioenergy, Seville, Spain, and St Louis, Mo. The ethanol-from-biomass plant, which has a 5-million-liter/yr capacity from a feed of  70 metric tons/d of agricultural residue, has been constructed alongside a far larger (195-million-liter/yr) cereal ethanol plant to benefit from its infrastructure. Abengoa, the world’s second largest bioethanol producer, is utilizing some of the latest technologies in the new plant, including a continuous biomass pretreatment system from SunOpta, Toronto, Ont., and new enzymes from Novozymes A/S, Bagsvaerd, Denmark, and Franklinton, N.C., developed in conjunction with the DOE’s National Renewable Energy Laboratory, Golden, Colo.

In June 2006, both SunOpta and Novozymes signed a contract with China Resource Alcohol Corp. (CRAC) for a cellulosic-ethanol demonstration plant in ZhaoDong City, China. CRAC’s goal is to install 1.7-million-gal/yr capacity by the end of this year and 330 million gal/yr by 2012.

Another major cellulosic-ethanol project in the works is a 30-million-liter/yr unit in Orange County, Calif., that will use process technology from Arkenol, Irvine, Calif. The plant, being engineered by JGC Corp., Yokohama, Japan, and Houston, Texas, is due for start-up early in 2009.

Going beyond fuels

For biorefineries to fulfill their promise, however, downstream markets other than those for fuels also need attention. “It seems unlikely that fuel from a biorefinery — at least in the beginning — is going to be as cost-effective as fuel from traditional fossil sources. To make the biorefinery sustainable, we must therefore do everything we can to help the economics,” says Charles Eckert, a professor in the school of chemical and biomolecular engineering at the Georgia Institute of Technology, Atlanta, Ga., and another Presidential Green Chemistry Challenge award winner.

Eckert and a colleague, Charles Liotta, won the 2004 Presidential award for their development of benign tunable solvents that couple reaction and separation processes. They are now collaborating with other researchers on the potential for producing high-value (up to $25/lb) specialty chemicals, pharmaceutical precursors and flavorings as “side stream” chemicals from the ethanol process (Figure 1).

Figure 1. Researcher Liz Hill withdraws a sample from a high-pressure reactor being used for making specialty chemicals from ethanol feedstocks.

Figure 1. Researcher Liz Hill withdraws a sample from a high-pressure reactor being used for making specialty chemicals from ethanol feedstocks.

“These are novel feedstocks for chemical production,” Eckert notes. “They are very different from what we’ve dealt with before. This gives us different challenges and provides a rich area for interdisciplinary research." Working as part of a research alliance with Oak Ridge National Laboratory, Oak Ridge, Tenn., and Imperial College, London, U.K., the team is exploring solvent techniques such as the use of near-critical water (pressurized water at 250°C to 300°C), gas-expanded liquids (such as CO2 in methanol) and supercritical fluids (CO2 under high pressure).

Meanwhile at the reaction level, Isis Innovation, Oxford, U.K., a company that promotes commercialization of developments at Oxford University, has licensed its Cytochrome P-450 designer enzyme technology to Industrial Biotechnology Corp. (IBC), Sarasota, Fla. Developed at the university by chemistry professor Luet Wong, the P-450 technology applies specific enzymes as biocatalysts for the conversion, often in a single step, of relatively low value substrates into high value chemicals. IBC says the potential market embraces more than 15,000 commercially available chemicals, including various alcohols, aldehydes, ketones and carboxylic acids.

Plastics’ progress

The production of plastics from renewable resources provides another example of how green technologies could change the face of the chemical industry. In 2006, for example, Archer Daniels Midland announced plans to build the first commercial plant to produce PHAs (polyhydroxylalkanoates), a family of biodegradable high-performance plastics that can be used in many applications currently served by petrochemical plastics — e.g., coatings, film and molded goods. Due for completion by the middle of 2008, the 50,000-ton/yr plant at Clinton, Iowa, will serve the joint venture set up between ADM and Metabolix, Cambridge, Mass., the company that developed the proprietary PHA technology and won a Presidential Award in 2004 for its work on commercializing bioplastics through the use of metabolic engineering and molecular biology.

Commenting on the joint venture, Jim Barber, Metabolix president and CEO, says “a broadly useful family of bio-based, biodegradable natural plastics will be commercially available for the first time.” Located next to ADM’s existing wet corn mill at Clinton, the PHA plant will take starch from the mill as its raw material.

Cargill subsidiary NatureWorks, Minnetonka, Minn., already offers a biodegradable plastic. Its polylactic acid (PLA) polymer is produced from corn at a 140,000-metric-ton/yr plant in Blair, Neb. PLA already has won a significant place in biodegradable packaging; Wal-Mart switched to PLA packaging for its fruit and herbs in 2005.

Not content with producing an inherently biodegradable product from a renewable feedstock, however, the NatureWorks plant has taken the application of green technology even further. Through the purchase of renewable energy certificates it has effectively replaced all the fossil-based electricity used in the plant with wind power. And, according to the company, by buying additional certificates to offset remaining greenhouse gas emissions, its PLA will be the world’s first and only greenhouse-gas-neutral polymer. Strictly speaking, PLA polymers fall more within the definition of compostable rather than biodegradable materials at least in the U.S. (The difference is one of timescale and the ambient conditions required for each.) They can, however, also be recycled, which for the moment is arguably one of the few ways for petrochemical-based plastics to carry a “green” label — a case in point being the new use for recycled polyethylene terephthalate (PET) waste developed by GE Plastics, Pittsfield, Mass.

Plastic-waste feedstock

GE has developed a new route to polybutylene terephthalate (PBT) based resins and polyester-based elastomers that uses PET waste — mainly from plastic bottles — as most of its feedstock. According to Vikram Gopal, GE Plastics’ program manager for crystalline plastics, the PET is first depolymerized and then chemically upgraded so it can be reacted with butanediol (BDO) — one of the main feedstocks in the conventional process — to produce PBT. The recycled-waste-based material supplants the other conventional feedstocks, either dimethyl terephthalate (DMT) or terephthalic acid (TPA). In all, more than 85% of PBT’s usual feedstocks are replaced by this “post-consumer feedstock.” The Valox iQ and Xenoy iQ resins made from the new PBT-based polymers are initially targeted at automotive applications (Figure 2).

 

Figure 2. New Xenoy iQ resins, initially aimed at automotive applications, are made using recycled PET.
Figure 2. New Xenoy iQ resins, initially aimed at automotive applications, are made using recycled PET.

GE says that if all the PBT produced in 2005 had been in the form of Valox iQ and Xenoy iQ, it would have consumed more than 565,000 metric tons of PET waste, the equivalent of 22.5 billion plastic bottles. While those are certainly impressive “green” credentials, the figures also help to put some perspective on the scale of the green chemical industry as it currently stands. For example, the annual global production capacity for biodegradable materials amounts to only around 300,000 metric tons, with the NatureWorks plant accounting for almost half of that, according to industry association European Bioplastics, Berlin, Germany.

With retail giants like Wal-Mart already in the market for biodegradable packaging, this level of capacity undoubtedly only scratches the surface of the potential for this particular green chemistry.

On a wider front, the chemical industry clearly is starting to unwrap the potential benefits of “going green.”

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