waste management and reclamation of contaminated sites index: Pollution, the dirty face of development Studying environmental pollution at the University of Bologna

Green Chemistry, a contribution to Sustainable Development

Sustainable developmentDizionario, the keystone of technological progress in this new century, challenges chemical sciences to play a primary role in converting old technologies into new clean processes and in designing new products and new eco-compatible processes.
Green chemistryDizionario, that is to say sustainable chemistry, is the new philosophy of chemistry, whose aim is to correct present practices in order to prevent problems in the future.

The awareness that pollutionDizionario, especially air and water pollution, does not respect national borders urges governments to adopt internationally accepted environmental policies.  The most important environmental agencies, heavy industry and the world of chemistry in general, are developing and following a code of conduct focused on precise strategies for pollution prevention.

Fig. 1: Paul Anastas, one of the founders of Green Chemistry, has served in the National Security and International Activities Division in the White House Office of Science and Technology Policy since 1999. In 1991, he established the Green Chemistry Program, a partnership between industry, government and university, which was expanded to include the Presidential Green Chemistry Challenge Awards. He is now Director of the Green Chemistry Institute, Washington, DC.
 

Green chemistry essentially refers to the new sustainability priorities in technological and scientific innovation, on the basis of general rules stressing the need to abandon harmful productsDizionario and processes. Some strategies which can be adopted are:

  1. Optimisation of balance of global mass in order to minimize waste.
  2. Minimisation of energy consumption, e.g. designing processes at ambient temperature and pressure.
  3. Use of raw materials taken from renewable sources.
  4. Whenever possible, replacement of old compounds with others which maintain their functional efficiency while minimizing their toxic impact on the environment and human health.

Environment-oriented molecular design has led to innovations such as:

 

  Fig. 2: A supercritical CO2 reactor. Supercritical CO2 can be used as a reaction solvent, as starting material to be incorporated in a target molecule, for the extraction of natural products from vegetal tissues (caffeine from coffee, etc), or for the purification of active principles in drugs.
(Credit: Organichem Corporation)
  1. Replacement of organic solvents with supercritical liquids. Supercritical carbon dioxide (T ≥ 13.1°C, P ≥ 74 bar) is often an exceptional substitute for organic solvents, in terms of hazard and environmental impact reduction. It can be used in dry cleaning as an alternative to chlorinated solvents, in semiconductor production and, finally, as a reaction or extraction solvent.
     
  2. Replacement of brominated flame retardants. Flame retardants are used as plastic material additives in a variety of products, furnishings, textiles and electronic equipment.  The most commonly used are aromatic compounds containing bromine which, apart from remaining persistently in the environment, are capable of bioaccumulatingDizionario in organisms and having a harmful effect on our health.  In order to avoid these problems, the big chemical companies are racing to find alternatives free of bromine, made up for example of a mix of epoxy resins and inter metal oxides.

    3.  
  3. Replacement of non-selective persistent pesticides. Polychlorinated pesticides (aldrin) have been widely used in agriculture for the last 50 years; they are very resistant to chemical and microbiological breakdown in the environment and they are bioaccumulated by organisms. Nowadays, a lot of effort is directed to finding alternative products, such as synthetic pyrethroids, analogues of the natural product pyrethrine. Since natural pyrethrine is particularly instable in the environment, analogues are designed which are more stable than the natural compound and above all much less toxic for higher organisms.
    Fig. 3: A pesticide spray operation for fruit trees and fields; from an environmental point of view, a pesticide must be effective, selective (able to spare other forms of life including insects needed for pollination) and not persistent, in order to avoid bioaccumulation or transport to groundwaters.
    (    Credit: USDA, Photo by: Tim McCabe)

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