Green chemistry is the use of chemistry for preventing environment pollution in order to protect human health. It may give the impression that it is branch of chemistry involving plants, which is not true.
Green chemistry encompasses all aspects and types of chemical process including synthesis, catalysis, analysis, monitoring, separations and reaction conditions, which reduce or eliminate the use or generation of hazardous substances.
Green chemistry is a highly effective approach to pollution prevention
as it applies innovative scientific solutions to real world
environmental problems. Chemical technologies are looked at during their
design, manufacture and use as chemical process and products having
broad application in industry. The substances include feedstock,
reagents, solvents, products and by products.
Green chemistry technologies can be categorized into one or more of the following focus areas.
- The use of alternative synthetic pathways for green chemistry.
- The use of alternative reaction conditions for green chemistry.
- The design of chemicals that are less toxic than current alternatives or inherently safer with regard to accident potential.
By offering environmentally safe alternatives to the more hazardous
chemicals and processes used in consumer and industrial applications,
the use of alternative synthetic pathways for green chemistry is
promoting pollution prevention at the molecular level.
Green chemistry may be defined as "the design of new chemical products
and processes, (or making improvements in already existing compounds and
processes), so as to reduce or eliminate the use and generation of
hazardous substances, making them less harmful to human health and
By reducing or eliminating the use or generation of these
hazardous substances, chemists can greatly reduce the risk to human
health and environment.
The phrase green chemistry was used by the scientists in USA, shortly
after the passing of the USA Prevention of pollution act 1990. A series
of grants were made available by the US Government to promote the field
of green chemistry by research into pollution prevention in the design
and synthesis of chemicals. The green chemistry programme is now a world
wide effort of many governments, academia, scientific societies,
industry, trade organizations, small business, non government
organizations, research centers and other government agencies to promote
the use of chemistry for pollution prevention through completely
voluntary, non-regulatory partnerships.
Over the past several years, international efforts in the field of
green chemistry have greatly increased the hopes of combating the most
pressing environmental problems such as water pollution, global warming and ozone depletion,
etc. International Union of Pure and Applied Chemistry (IUPAC) and the
management organization of Green Chemistry Institute have been working
in collaboration with industry and other research institutions world
wide, to help solve these pollution and other related problems.
The 12 principles of green chemistry are listed below. Of course over the years additional principles have been added to these original 12, but those could be derived from these 12 principles.
- Prevention - It is better to prevent waste than to treat or clean it up after it has been generated in a process. This is based on the concept of "stop the pollutant at the source."
- Atom economy - Synthetic steps or reactions should be designed to maximize the incorporation of all raw materials used in the process into the final product, instead of generating unwanted side or wasteful products.
- Less hazardous chemical use - Synthetic methods should be designed to use and generate substances that posses little or no toxicity to the environment and public at large.
- Design for safer chemicals - Chemical products should be designed so that they not only perform their designed function but are also less toxic in the short and long terms.
- Safer solvents and auxiliaries - The use of auxiliary substances such as solvents or separation agents should not be used whenever possible. If their use cannot be avoided, they should be used as mildly or innocuously as possible.
- Design for energy efficiency - Energy requirements of chemical processes should be recognized for their environmental and economic impacts and should be minimized. If possible all reactions should be conducted at mild temperature and pressure.
- Use of renewable feedstock - A raw material or feedstock should be renewable rather than depleting whenever technically and economically practicable. For example, oil, gas and coal are dwindling resources that cannot be replenished.
- Reduction of derivatives - Use of blocking groups, protection / deprotection and temporary modification of physical chemical processes is known as derivatization, which is normally practiced during chemical synthesis. Unnecessary derivatization should be minimized or avoided. Such steps require additional reagents and energy and can generate waste.
- Catalysis - Catalytic reagents are superior to stoichiometric reagents. The use of heterogeneous catalysts has several advantages over the use of homogeneous or liquid catalysts. Use of oxidation catalysts and air is better than using stoichiometric quantities of oxidizing agents.
- Design for degradation - Chemical products should be designed so that at the end of their function they break down into innocuous degradation products and do not persist in the environment. A life cycle analysis will help in understanding its persistence in nature.
- Real-time analysis for pollution prevention - Analytical methodologies need to be improved to allow for real-time in process monitoring and control prior to the formation of hazardous substances.
- Inherently safer chemistry for accident prevention - Substances and the form of a substance used in a chemical process should be chosen to minimize the potential for chemical accidents including releases, storage of toxic chemicals, explosions and fires.
The key words in 12 principles of green chemistry are shown below.