After you finishing doing with your chemistry experiments at school, what would you do? You may pour the chemicals down the sink. Now imagine thousands of factories doing that, and you’ll realize there will be a problem. Luckily a solution is coming about – green chemistry.
Science and Sustainability
Every day, millions of tones of hazardous chemicals are buried underground, dumped into rivers, lakes and seas or spewed into the air. The aim of green chemistry is to develop new methods that reduce and prevent pollution.
Paul Anastas and John C. Warner of the U.S. Environmental Protection Agency laid out the Twelve Principles of green chemistry. They are:
- It is better to prevent waste than to treat it after it is formed.
- Methods for making new chemicals should be designed so that all the materials used in the reaction become part of the final product.
- These methods should use and generate substances that possess zero danger to human health and the environment.
- ‘Green’ chemical products should work as well as others, and still be less toxic.
The use of ‘auxiliaries’ i.e. substances like solvents, purification agents etc., should be made unnecessary; or harmless substances should be used.
- ‘Green’ reactions should minimize the need for conditions like high pressure or low temperature. Instead, they should be possible at normal temperature and pressure.
- A raw material should be renewable (e.g. like biogas) rather than deplete the natural resource (like coal).
- A ‘green’ process should reduce the number of steps, and therefore the need for intermediate products.
- Reagents that can be used again and again (called catalytic reagents) should be used instead of those that are needed in large quantities (stoichiometric reagents).
A ‘green’ chemical product should be designed so that when it is not needed, it can break down into harmless chemicals.
- A ‘green’ process should allow for monitoring and control in order to prevent the formation of hazardous substances.
- A ‘green’ substance or process should not carry a risk for a chemical accident, such as a fire or leak of dangerous substance.
You can see that green chemistry has many challenges ahead of it. To encourage scientists, many countries offer prizes for new technologies that follow these principles. These include the US, UK, Australia, Japan and Canada. In India, the pioneer of Green Chemistry is the Tata Chemicals Innovation Centre in Pune.
Advances in Green Chemistry
A few technical advancements have been made so far. One of the most important is the use of ‘dry media reactions’. In this, the reagents are embedded in a dry material, rather than dissolved in a solvent. The matrix can be recycled after the reaction is over, thus eliminating what would otherwise have been a huge waste of solvent.
A company called NatureWorks has developed a new packaging material called polylactic acid (PLA,its CAS number is 26100-51-6) using the above principles. The advantage of PLA is that it is not wasteful to make, and can be recycled. If you forget to recycle it and throw it away instead, it is degraded by bacteria into harmless substances.
How can you do?
You too, can make a contribution to green chemistry by taking a small pledge, when you do your chemistry practicals. Use as little of the chemicals you need; Don’t pour hazardous substances down the sink, dispose it through the correct methods; Work out the reaction carefully in your notebook before you do it in the lab; If your reaction needs heating or cooling, do it for the minimum time needed; If you follow the pledge, you’ll not only have a greener experience, but a safer and more scientific one too.