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So what is green chemistry?
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Written by Sarah Steely
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Saturday, 17 May 2008
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 There has been an ongoing debate over the hazardous nature of various synthetic chemicals that have been released into the environment. The many uncertainties with toxicological data (such as exposure, fate, and transport data) for a variety of chemicals has led to a debate over what to do. Anastas and Warner (1998) say that there are two choices for the scientific community: they can either allow the uncertainties to continue to paralyze any progress and not address the concerns of human health and the environment, or they can accept that there is a detrimental risk and effect from the release of these chemicals and do something about it. Chemists, specifically synthetic chemists, have considerable control over this debate since it is they who command the knowledge and power to develop alternatives and solutions through their trade.
Green chemistry is “the utilization of a set of principles that reduces or eliminates the use or generation of hazardous substances in the design, manufacture and application of chemical products (Anastas and Warner 1998).” It uses chemistry as a type of pollution prevention that “provides a fundamental methodology for changing the intrinsic nature of a chemical product or process so that it is inherently of less risk to human health and the environment (Anastas and Warner 1998).” It achieves this through the design and redesign of chemical syntheses and chemical products to prevent the pollution or to help solve environmental problems.
A set of 12 principles have been generated for those who wish to use green chemistry (Anastas and Warner 1998). These principles have been adopted by the EPA and other institutions to help train their chemists in methods of better synthesis. Many universities are now offering courses in Green Chemistry in order to train the future’s synthetic chemists to approach synthesis with an environmentally and socially conscious mindset. These principles are:
1. It is better to prevent waste than to treat or clean up waste after it is formed.
2. Synthetic methods should be designed to maximize the incorporation of all materials used in the process into the final product.
3. Wherever practicable, synthetic methadologies should be designed to use and generate substances that possess little or no toxicity to human health and the environment.
4. Chemical products should be designed to preserve efficacy of function while reducing toxicity.
5. The use of auxilliary substances (e.g. solvents, separation agents, etc.) should be made unnecessary wherever possible and, innocuous when used.
6. Energy requirements should be recognized for their environmental and economic impacts and should be minimized. Synthetic methods should be conducted at ambient temperature and pressure.
7. A raw material or feedstock should be renewable rather than depleting wherever technically and economically practicable.
8. Unnecessary derivatization (blocking group, protection/deprotection, temporary modification of physical/chemical processes) should be avoided whenever possible.
9. Catalytic reagents (as selective as possible) are superior to stoichiometric reagents.
10. Chemical products should be designed so that at the end of their function they do not persist in the environment and break down into innocuous degradation products.
11. Analytical methadologies need to be further developed to allow for real-time, in-process monitoring and control prior to the formation of hazardous substances.
12. Substances and the form of a substance used in a chemical process should be chosed so as to minimize the potential for chemical accidents, including releases, explosions, and fires.
Changing the synthesis of a particular chemical to fit these principles is not easy since these changes affect the entire process and life cycle of the product. One of the goals of green chemistry is to improve where improvement can be made since it is recognized that many hazardous substances still are the most efficient way to go about certain forms of synthesis. However, there have been many advances over the last decade in the area of green chemistry that have led to substituted substances that are just as efficient and less toxic. (Anastas and Williamson 1996)
Some of these advances include designing products to be biodegradable, the synthesis of vitamin C in a more energy efficient and environmentally friendly way, less toxic steps in leather manufacturing and tanning, less toxic synthetic dyes, less toxic fluorescent brightening agents in textiles and paper, and more ‘eco-friendly’ synthetic pesticides for crops. (Lancaster 2002) There is an expanding body of literature that deals with using supercritical (liquid like density and solvent strength) carbon dioxide as a substitute solvent in chemical synthesis and catalysis (Anastas and Williamson 1996). One of the many advantages include recycling CO2 emissions from another sector of industry and using that to replace toxic solvents in a synthesis, thereby recycling a greenhouse gas and preventing hazardous waste. Dow Chemical Company also uses recycled CO2 as a blowing agent for the manufacture of polystyrene foam sheets. It is a non-flammable and a cost-effective alternative, meaning there is increased worker safety and along with economic benefits. (Anastas and Warner 1998)
Green chemistry is a growing field of study, active research and it has great potential to help mitigate our unsustainable culture. It may not be the ultimate solution, but green chemistry is certainly a step in the right direction, and any action that can help us reduce manufacturing wastes should be encouraged. So three cheers for chemistry!
References Cited
Anastas, P. and Williamson, T., eds.(1996) Green Chemistry; Designing Chemistry for
the Environment. Washington, DC: American Chemical Society.
Anastas, P. and Warner, J. (1998) Green Chemistry: Theory and Practice. New York:
Oxford University Press.
Lancaster, M. (2002) Green Chemistry; An Introductory Text. Cambridge, UK : Royal
Society of Chemistry.
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Last Updated ( Monday, 14 July 2008 )
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