Green chemistry, which came about in the 1990s, is aimed at designing and developing products (and chemical processes) to cut down on, or cut out, the use and synthesis of dangerous substances.
According to the CEA (the French Atomic Energy and Alternative Energies Commission), green chemistry draws its inspiration from the concept of sustainable development. It incorporates the following: optimisation of processes’ energy efficiency and energy expenditure; sparing use and recycling of raw materials; and sparing use and recycling of by-products from chemical reactions. Green chemistry also aims to cut down on final waste – entailing, of course, a reduction in its impact on human health and the environment.
1 – First and foremost, reducing the chemical footprint
Green chemistry – also known as sustainable chemistry, eco-friendly chemistry or renewable chemistry – sets out principles to cut down on, and cut out, the use and generation of substances that are harmful to the environment. This is carried out using new chemical processes that are “clean”, meaning respectful of the environment. Having developed throughout the 20th century relying on hydrocarbon derivatives, industrial chemistry must gravitate towards more virtuous principles in order to safeguard both the environment and human health (faced with the growing number of pathologies being diagnosed: cancer, diabetes, Alzheimer’s disease, autism).
Moreover, one of the major endeavours of this green chemistry is to achieve a reduction in the large-scale production of substances known as CMRs (those that are carcinogenic, mutagenic or toxic to reproduction) and of endocrine disruptors.
The other major endeavours of this green chemistry are:
- To achieve a reduction in dependency on non-renewable energy sources and in industry’s carbon footprint
- The issue of waste which is disposed of and disintegrates in rubbish dumps
- The wish to take advantage of certain resources that are plentiful yet go unused, like carbon dioxide
2 – Abiding by the 12 founding principles of green chemistry
The concept of green chemistry appeared in the USA in the 1990s. In 1998, Paul Anastas and John Warner, researchers at the Environmental Protection Agency (EPA), laid out the theoretical bases of this new discipline by publishing a book setting forth 12 founding principles.
It’s better to avoid generating waste in the first place than to have to subsequently process or dispose of it.
2. Using atoms sparingly
Implementation of synthesis methods that incorporate all of the materials involved in the process into the finished product.
3. Designing less dangerous synthesis methods
Insofar as is possible, synthesis methods must use and produce substances that are low toxicity (or non-toxic) to human beings and without consequences for the environment.
4. Designing safer chemicals
Development of chemicals that attain the properties sought while being as least toxic as possible.
5. Less polluting solvents and adjuvants
Dropping the use of artificial adjuvants (solvents, separation agents, etc.), or opting for harmless adjuvants if they are required. Unconventional activation methods may be used: use of water as a solvent, of supercritical fluids, microwave heating, replacement with ionic liquids, etc.
6. Seeking an energy yield
The energy expenditure required for chemical reactions must be commensurate with its impact on the environment and economy, and thereby reduced to a minimum. Insofar as is possible, synthesis operations must be conducted under ambient temperature and pressure conditions.
7. Using renewable resources
Using natural resources or renewable raw materials rather than fossil substances, insofar as technical means and finances allow.
8. Reducing the number of derivatives
If possible, avoiding pointlessly creating multiple derivatives that require excessive amounts of reagents and may generate waste.
Favour catalytic solutions that are recyclable. A catalyst is a substance added to a chemical solution to prompt a chemical reaction. It accelerates the reaction while lowering its energy and comes through the chemical process unchanged, which is why it is recyclable.
10. Product design with a view to degradability
Chemicals must be designed to disintegrate into harmless biodegradable waste once used.
11. Real-time observation with a view to preventing pollution
Observation methods must be honed and thereby allow for real-time monitoring and checking of ongoing operations, and must track them to pick up on any formation of dangerous substances.
12. Chemistry that’s fundamentally more reliable
The choice of substances and chemical processes involving them must foresee the risk of accidents (release of dangerous fumes, explosions and fires).
The triumphs of green chemistry
In 2005, Japanese chemist Ryoji Noyori identified three keys to promoting the development of green chemistry: the use of carbon dioxide (CO2) in a supercritical fluid state as a “green solvent”; the use of aqueous hydrogen peroxide to refine oxidation; and the use of hydrogen in asymmetrical syntheses.
An interesting point – the chemists discovered that when CO2 molecules are kept in a transitive state (halfway between liquid and gaseous states), the gas works like an industrial refrigerant. The applications of this CO2, which is known as “transcritical”, make it possible to create refrigeration conditions in supermarkets, agri-food factories, warehouses, ice rinks and delivery trucks.
So if chlorofluorocarbons and hydrofluorocarbons (greenhouse gases commonly used for refrigeration) are replaced with this same transcritical CO2, ecological impact is reduced by around 15%.
When it comes to beauty products, this transcritical CO2 plays a part in the green extraction process in respect of odorant molecules used to formulate perfumes. It also makes it possible for decaffeination to take place.
Bioengineering is also a promising technique, with the completion of chemical processes inside organisms (living cells).
Polyethylene (PET) is light and robust, and is the most widely-used type of plastic (for water and shampoo bottles, plastic bags, packaging items). With its extremely stable molecular structure, PET does not break down easily. But Japanese researchers have discovered a bacterium that makes it disintegrate, and even enzymes that accelerate this disintegration process!
Researchers at Stanford University in California have found a way to produce plastic without using petrochemical oil. Instead, it is made from CO2 and industrial by-products or farm waste (fibres left over from carrot juice production).
At first, chemistry and green seemed like a contradiction in terms. However, it’s clear that green chemistry has pulled off the punt of reducing the production and use of a few materials that are dangerous to both human health and the planet. But it still has a long way to go.