Green Chemistry





Green Chemistry 3584
Photo by: lefameux

The term green chemistry, coined in 1991, is defined as "the design of chemical products and processes that reduce or eliminate the use and generation of hazardous substances." This approach to the protection of human health and the environment represents a significant departure from the traditional methods previously used. Although historically societies have tried to minimize exposure to chemicals, green chemistry emphasizes the design and creation of chemicals that are not hazardous to people or the environment. It has been applied to a wide range of industrial and consumer goods, including paints, dyes, fertilizers, pesticides, plastics, medicines, electronics, dry cleaning, energy generation, and water purification.

At the heart of green chemistry is the recognition that hazard is simply another property of a chemical substance. Properties of chemicals are caused by their molecular structure; they can be modified by changing that structure. The types of hazards that can be addressed by green chemistry vary. They include physical hazards (being explosive or flammable), toxicity (being carcinogenic or cancer causing, or lethal), or global hazards (climate change or stratospheric ozone depletion). Therefore, in the same way that a substance can be designed to be red or hard, it may also be designed to be nontoxic.


The Principles of Green Chemistry

Chemists and chemical engineers applying green chemistry look at the entire life cycle of a product or process, from the origins of the materials used for manufacturing to the ultimate fate of the materials after they have finished their useful life. By using such an approach, scientists have been able to reduce the impacts of harmful chemicals in the environment.

Research and development in the field of green chemistry are occurring in several different areas.

Alternative feedstocks. Historically, many of the materials used to make products often were toxic or depleted limited resources such as petroleum, but green chemistry research is developing ways to make products from renewable and nonhazardous substances, such as plants and agricultural wastes. For example, cellulose and hemicellulose, which constitute up to eighty percent of biomass, can be broken down to sugars, then fermented to chemical commodities such as ethanol, organic acids, glycols, and aldehydes. Converting biomass to ethanol has become economically and technically viable due to a new class of genetically modified bacteria capable of breaking down the different sugars in hemicellulose.

Benign manufacturing. The methods used to make chemical materials, called synthetic methods, have often employed toxic chemicals such as cyanide or chlorine. In addition, these methods have at times generated large quantities of hazardous wastes. Green chemistry research is developing new ways to make these synthetic methods more efficient and to minimize wastes while also ensuring that the chemicals used and generated by these methods are as nonhazardous as possible. For example, a number of industries, such as the pulp and paper industry, use chlorine compounds in processes that generate toxic chlorinated organic waste. Green chemists have developed a new technology that converts wood pulp into paper using oxygen, water and polyoxometalate salts, while producing only water and carbon dioxide as by-products.

Designing safer chemicals. Once it is certain that the feedstocks and methods needed to make a substance are environmentally benign, it is important to ensure that the end product is as nontoxic as possible. By understanding what makes something harmful (the field of molecular toxicology), scientists are able to design the molecular structure so that it is not dangerous.

Green analytical chemistry. The detection, measurement, and monitoring of chemicals in the environment through analytical chemistry have long been a tool for environmental protection. Instead of measuring environmental problems after they occur, however, green chemistry seeks to prevent the formation of toxic substances and thus prevent such problems. By making sensors and other instruments part of industrial manufacturing processes, green analytical chemistry is able to detect even tiny amounts of a toxic substance and to adjust process controls to minimize or stop its formation altogether. In addition, although traditional methods of analytical chemistry employ substances such as hazardous solvents, green analytical methods are being developed to minimize the use and generation of these substances while conducting analysis.


Why Green Chemistry?

Green chemistry is effective in reducing the impact of chemicals on human health and the environment. In addition, many companies have found that it can be cheaper and even profitable to meet environmental goals. Profits derive from higher efficiency, less waste, better product quality, and reduced liability. Many environmental laws and regulations target hazardous chemicals, and following all these requirements can be complicated. But green chemistry allows companies to comply with the law in much simpler and cheaper ways. Finally, green chemistry is a fundamental science-based approach. Addressing the problem of hazard at the molecular level, it can be applied to all kinds of environmental issues.

Since 1991, there have been many advances in green chemistry, in both academic research and industrial implementation. For example, Spinosad, an insecticide manufactured by fermenting a naturally occurring soil organism, was registered by the EPA as a reduced-risk insecticide in 1997. Spinosad does not leach, bioaccumulate, volatilize, or persist in the environment and in field tests left 70 to 90 percent of beneficial insects unharmed. It has a relatively low toxicity to mammals and birds and is slightly to moderately toxic to aquatic organisms, but is toxic to bees until it dries. In another advance, an industrial cleaning solvent, ethyl lactate, made from cornstarch and soybean oil was patented in 2000 and is competitively priced with petrochemical solvents. It biodegrades to carbon dioxide and water and has no known harmful effects for the environment, humans, or wildlife. These advances, however, represent an extremely small fraction of the potential applications of green chemistry. Because the products and processes that form the basis of the economy and infrastructure are based on the design and utilization of chemicals and materials, the challenges facing this field are enormous.

SEE ALSO B IODEGRADATION ; R ENEWABLE E NERGY .

Bibliography

Anastas, Paul T., and Warner, John C. (1995). Green Chemistry: Theory and Practice. New York: Oxford University Press.


Internet Resources

Green Chemistry Institute at the American Chemical Society. "Green Chemistry Institute." Available from http://www.acs.org/greenchemistryinstitute .

U.S. Environmental Protection Agency. "EPA's Green Chemistry Program." Available from http://www.epa.gov/greenchemistry .

Paul T. Anastas



User Contributions:

Comment about this article, ask questions, or add new information about this topic:

CAPTCHA


Green Chemistry forum