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Replacing Toxic Solvents with Carbon Dioxide

Organic solvents, such as perchloroethylene (perc), are used in hundreds of industrial processes ranging from manufacturing Teflon to developing film. Some of these solvents are highly toxic or can break down into ozone-depleting gases, and some processes contaminate billions of gallons of wastewater. Given these detrimental environmental impacts, the TSE program funded research to identify alternatives to organic solvent-based processes.

Dr. Joseph DeSimone from the University of North Carolina at Chapel Hill received a TSE grant from EPA in 1997 to develop carbon dioxide-based solvents. His previous research had shown that carbon dioxide (CO2) in its liquid and supercritical states is an excellent environmentallybenign alternative solvent to chlorofluorocarbons dissolved in water. Under the TSE grant, Dr. DeSimone and his collaborators developed detergent-like "surfactants" that allow CO2 to dissolve substances that would not normally be soluble. One of the consumer applications of this research is an alternative dry cleaning solution that replaces perchloroethylene. This detergent system is now used in more than 100 dry cleaning establishments in over 12 states.

A follow-up grant to Dr. DeSimone in 2001 allowed him to extend this solvent research into applications for the microelectronics industries. To produce a single computer chip, conventional lithography techniques use one kilogram of organic solvent and aqueous waste. The CO2-based process that Dr. DeSimone is developing to produce these multi-layer integrated circuits is environmentally benign, ensuring that this and other future manufacturing processes have minimal impact on the environment. The technology also provides solutions to some of the challenges associated with traditional water-based processes, such as achieving film uniformity while spin-coating wafers.

In addition to his TSE research, Dr. Simone co-founded MiCELL Technologies, a start-up company committed to developing and marketing carbon dioxide-based technologies. MiCELL currently owns or has licensing rights to 77 patents in the United States, with an additional eight applications pending.

Dr. DeSimone was appointed the director of the National Science Foundation's Science and Technology Center for Environmentally Responsible Solvents and Processes. In early 2005, he was elected into the National Academy of Arts and Sciences and into the National Academy of Engineering as its youngest member.

From Soybeans, Chicken Feathers, and Newspapers to High-Performance Composites and Resins

Dr. Richard Wool at the University of Delaware is using plant oils and waste products to develop the worlds cheapest composites and resins. From tractor parts made with soybean-based plastics to circuit board material produced using chicken feathers, to hurricane-resistant roofing fashioned from recycled newspaper, Dr. Wool has made use of renewable, biologically based materials to create environmentally friendly products. Because of the low cost of plant oil (10 to 15 cents per pound) and natural fibers, these technology breakthroughs are increasing the available options for manufacturers and making sustainable living a reality.

Dr. Wool received a TSE grant from EPA in January 2002 to study fundamental issues pertaining to the cost-effective synthesis and manufacture of plant-based resins and composites. These biologically based materials provide alternatives to petroleum-derived plastics. As a direct result of this research, Dr. Wool helped develop a new universal theory of fracture polymers, applied for five patents, and collaborated with nine industrial partners.

Currently, the John Deere Company uses Dr. Wools soybean oil plastics to manufacture parts for its tractors, and his chicken feather circuit board material has attracted the interest of Intel. Additionally, Dr. Wools hurricane-resistant roofing received attention from the news media and architecture societies including Newsweek, Architectural Record, and the RIBA Journal (the magazine of the Royal Institute of British Architects). The roofing is built primarily from recycled newspaper, chicken feathers, and soybean-derived plastics that are processed into a single, specially fitted lightweight roof. Its storm-resistant design could greatly reduce the millions of dollars of damage to homes in regions affected by hurricanes. In addition to the safety factor, its foam-core engineered structure imparts huge thermal energy savings, a benefit to both the environment and consumers. This roofing has the potential to become the countrys highest-volume application of bio-based composite materials derived from low-cost, environmentally friendly, renewable resources.

These biologically based composite materials could make a considerable positive impact on the environment. If they are commercialized and produced in large quantities, each pound of plant or beans used would save about a poundof fossil fuel. In addition, the substitution of 10 billion kilos of soybean-based products for fossil fuel-based plastics would be equivalent to reducing carbon dioxide emissions by 300 billion pounds per year.

This research extends into the classroom, furthering its impact by educating the next generation of green chemistry and engineering researchers. The TSE grant provided partial funding for four graduate and ten undergraduate students to train with Dr. Wool, and many of these students have gone on to careers in environmentally related research. To promote both the growing interest from students and the growing need from industry, Dr. Wool also developed a course on green engineering for undergraduates at the University of Delaware.

Streamlining Waste Management with Electronic Tags for Trash

Dr. Valerie Thomas at Princeton University received a TSE grant from EPA in 2002 to develop electronic tags that could be used to monitor waste and recycling. Her work aims to increase recycling efficiency by using information technology solutions for identification and sorting.

There is currently no system in place to track non-hazardous waste and recyclables as they move through the waste management system in the United States. Dr. Thomas research examines the options that are available for implementing such a system, focusing on the feasibility of different technologies such as barcodes, radio frequency identification (RFID) tags, and global positioning system (GPS) transmitters. Such systems potentially could track a product throughout its lifecycle while feeding back important data on product distribution, consumption, use, disposal, and recycling. Identification of products also will make recycling easier and cheaper, allowing a larger recovery of economic value from the waste stream.

Dr. Thomas collaborated with Motorola to develop a working prototype barcode system to aid in recycling Motorola cell phones. With Princeton undergraduate student Steven Saar, Dr. Thomas developed Web-based software that recognizes the scanned barcode on a Motorola phone and provides disassembly instructions for that particular model. The software has not been patented in order to promote development of similar waste management systems, but Motorola wrote an intellectual property disclosure naming Dr. Thomas, Saar, and a collaborator at Motorola as the developers of the technology. Saars work on the barcode-tracking software for Motorola helped secure him a job with Intel after he graduated in 2004. Audrey Lee, a Ph.D. graduate student in electrical engineering, won a Student Paper Award in May 2004 from the Institute for Electronic and Electrical Engineers for a paper she and Dr. Thomas wrote using the findings from the TSE grant. Lees work with Dr. Thomas on electronic tags allowed her to redirect her thesis toward environmentally relevant issues.

Also as a result of this research, funded almost entirely by the TSE grant, Dr. Thomas was able to win a competitive position working on energy policy as Congressional Science Fellow to New Jersey Congressman Rush Holt and to secure a position at the Georgia Institute of Technology. There, she will continue to develop a practical method of labeling waste and recycling products for use in U.S. towns and cities.

New Technique Reduces Foundry VOC Emissions

Dr. Fred Cannon and his team from the University of Pennsylvania are studying an advanced oxidation (AO) process that can be used to prevent pollution from foundries. Dr. Cannon received a TSE grant from EPA in 2002 to study and improve the AO process based on data from five full-scale foundries where the new technique is in use. The metal casting industry represents a significant manufacturing sector of the U.S. economy, with approximately 3,000 foundries across the country. The AO process is applicable to foundries that use green sand molds, which includes 60 percent of foundries in the U.S. The new process has been shown to greatly reduce the emission of hazardous air pollutants from the foundries where it is installed, including toxic volatile organic compounds (VOCs), benzene, and carbon monoxide.

Dr. Cannon and his team have demonstrated reductions in VOC emissions ranging from 20 to 75 percent at the five foundries where the process is currently installed and predict that it can be improved to consistently reduce up to 80 percent of emissions. Using this as an estimate of potential pollution reduction, this process alone could reduce over 2.5 million pounds of VOCs each year.

In addition to this environmental benefit, the process is more efficient and thus more economically profitable. The AO process has reduced the amount of clay, coal, and sand required for casting by up to 40 percent and decreased the number of casting defects by 35 percent.

Lead-Free Molecular Wires for Household Electronics

Dr. C.P. Wong from the Georgia Institute of Technology received a TSE grant from EPA in December 2003 to develop a substitute for leaded solder, which is used broadly in the electronics industry. Lead is recognized as a carcinogen, a developmental toxicant, a reproductive toxicant, and is suspected to be a neurological toxicant. Its use in household electronics, such as computers, personal digital assistants (PDAs), and cell phones, has attracted scrutiny from regulatory agencies in Europe and Japan.

To date, most substitutes developed for leaded solder have been alloys that combine tin with metals such as silver, gold, copper, bismuth, or antimony. These have the disadvantage of higher manufacturing temperatures (up to 260 degrees Celsius), which necessitates higher energy costs and more expensive circuit board materials. With the assistance of graduate students Grace Yi Li and Kyoung-sik Moon, Dr. Wong is developing electrically conductive adhesives (ECAs) that are much better substitutes for leaded solder.

In addition to the benefits of reduced lead use, ECAs could simplify electronics manufacture by eliminating several processing steps. Because the ECAs can be cured at lower temperaturesabout 150 degrees Celsius and potentially even room temperaturethey would produce less thermal stress on components, require less energy, and enable the use of existing circuit board materials.3 If all of the current tin-lead solder in the U.S. were replaced with ECAs, energy savings for electronics manufacturing could be as much as 60 percent and the short-term consumption of lead potentially could drop by as much as 10 percent.

To overcome one of the main challenges of lead-free ECAs (the lower density of the electrical current, which is not adequate for many power-intensive devices), Dr. Wong and his collaborators developed self-assembled monolayers (SAM). SAM structures are molecular wires made of an organic polymer matrix that provide a direct electrical connection, bypassing resistance normally found at an interface. Georgia Institute of Technology has applied for patents on the SAM and is pursuing licensing of the technology with several companies.

Green Oxidation Catalysis

New and improved catalysts enable important chemical reactions to be conducted under milder conditions, with less energy expenditure, in a shorter time, using less reactive and more environmentally friendly chemicals and solvents. A TSE grant from NSF to Dr. Terry Collins of Carnegie Mellon University in 1996 led to the development of environmentally friendly oxidant activators. Dr. Collins won the 1999 Presidential Green Chemistry Challenge Award for this research.

In the paper manufacturing process, the newly developed activators catalyze the oxidizing ability of hydrogen peroxide, creating water and oxygen as byproducts of the bleaching process. The older methods relied on elemental chlorine-based catalysts and produced toxic dioxins that are known to accumulate and persist in the tissues of humans and animals. One of the alternative methods uses chlorine dioxide, which reduces dioxin emissions significantly but does not eliminate them.

The environmental benefits of the newly developed iron (III)-tetra-amidato macrocyclic ligand (or TAML) activators in paper manufacturing go beyond eliminating dioxin emissions and reducing wastewater production. First, TAML bleaching is more effective, leaving behind only a third of the lignin (the color-causing compound) of traditional bleaching methods. It also works most efficiently at lower temperatures, and the estimated savings from this benefit alone have been calculated at 23.2 million tons of coal per year if 100 percent of paper mills in the U.S. used the TAML activators.4 This paper bleaching technology has been patented, and license agreements for commercialization already are in place.

TAML oxidant activators also can be used for fuel desulfurization, easily removing more than 85 percent of recalcitrant sulfur compounds in refined fuels. Sulfur is associated with human health impacts, contributes to acid rain, and causes engines to burn less efficiently. The application of these activators in the fuel refining process could lead to cleaner fuels that have higher efficiency.

The laundry industry has also benefited from Dr. Collinss activators. TAML-activated peroxide in household bleaches provides the most attractive dye-transfer inhibition and improved stain removal properties.

The TAML-peroxide activators used in this process require less water than traditional processes offering both economic and environmental benefits. Dr. Collins and other researchers continue to develop additional uses for the TAML activators including water disinfection, degradation of persistent organic pollutants, and homeland security.

Growing Plastics from Plants

Polylactides (PLAs) are fully biodegradable, completely recyclable plastics derived entirely from a widely available and renewable resource: corn. Dr. John Dorgan at the Colorado School of Mines received a TSE grant from EPA in 1998 that helped fund the development of PLAs. Unlike traditional plastics, which are made from non-renewable fossil fuel feedstocks, PLA plastics are produced by the fermentation of corn. This process uses 30 to 50 percent less fossil resources and results in 50 to 70 percent lower carbon dioxide emissions than the typical polyethylene and nylon manufacturing processes for plastics. The production process also uses internal recycling to eliminate waste, preventing pollution at the source and resulting in greater than 95 percent yields.

Dr. Dorgans TSE grant, which was matched with financial support from Cargill-Dow, funded the research necessary to establish a fundamental scientific understanding of the properties of PLAs. Cargill-Dow now produces 300 million pounds of PLA each year at the words first global-scale manufacturing facility capable of making commercial-grade plastic resins from an annually renewable resource. The plant in Blair, Nebraska, employs close to 100 people and sells its biodegradable plastics to companies all over the world. Some of the everyday products made from PLA plastics include blister packs, floral wraps, tray inserts, and window films. A number of companies, including Wal-Mart and Del Monte, now use PLA for food packaging.

Dr. Dorgan and his colleagues characterized the basic chain properties of the PLAs, studied the plastics permeability to gases important to the packaging and food industries, developed a strengthened plastic that combines PLA with a secondary biodegradable plastic, and created a software simulation package which can help facilitate the change-over from the manufacture of traditional plastics to PLA plastics. The research has even led to PLA-based fibers, developed in collaboration with industry, receiving Federal Trade Commission classification as a new generic fiber joining the ranks of cotton, wool, silk, nylon, and polyesters. Seventeen publications and two graduate degree projects in chemical engineering resulted from the research.

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