Misc

Green chemistry: Small molecules with a big impact

Anthony Gentile & Eisha Ahmed October 7, 2021

There has been a growing emphasis on sustainability in recent decades, driven by the need to develop and adopt more environmentally friendly products and processes as we face the consequences of our polluting past. Chemistry and chemical engineering are an essential part of modern product development. This has driven the rapid growth of “Green Chemistry”, a diverse field of chemistry that focuses on sustainable product development to reduce or eliminate the production of harmful substances.

Non-sustainable products and processes are driving environmental destruction

Despite being highly economical and productive, many societal and manufacturing practices integral to modern society are contributing to increasing greenhouse gas emissions, deforestation, and release of environmental pollutants. This includes emissions from transportation, agriculture-driven deforestation, and product and package manufacturing, which results in a host of long-term ecological and economic consequences like rising temperatures, acid rain, rising sea levels, and severe droughts.

Chemistry is crucial to the production and life-cycle of most modern products. A growing awareness of these issues has driven the scientific community to develop new chemical processes that are environmentally sound, in an effort to reduce (or eliminate) the production of polluting substances by current technology. Rather than simply “cleaning-up” the mess created by non-sustainable practices, the objective is to prevent the production of damaging products and by-products in the first place.

The Emergence of “Green Chemistry”

The modern environmentalism movement was in full swing in the 1990s, during which there was a rising awareness of the negative environmental impact associated with existing practices in product development. That decade, the US Environmental Protection Agency (EPA) coined the term Green Chemistry, defined as ‘the design of chemical products and processes that reduce or eliminate the use or generation of hazardous substances”. Also known as sustainable chemistry, green chemistry aims to develop alternative products and processes that are more environmentally-friendly than conventional practices.

Green Chemistry’s 12 Guiding Principles

In 1998, Paul Anastas and John C. Warner published the 12 Principles of Green Chemistry to illustrate the goal and practice of green chemistry. 


The 12 Guiding Principles are as follows:

1. Prevent Waste

Prevent rather than treat and clean up waste after it has been created; prevention is better than cure!

2. Design Chemicals for Degradation

Chemical products should be created so that they can be discarded easily rather than be bioaccumulative and toxic. 

3. Design Less Hazardous Chemical Synthesis

Create chemicals that do not pose a harm to humans or the environment.

4. Increase Energy Efficiency

Minimize the energy used to create a chemical product or reaction.

5. Use Safer Solvents and Reaction Conditions

Chemical reactions typically require the use of solvents, which may be toxic or flammable; opt for reaction conditions that use safer chemicals.

6. Design Safer Chemicals and Products

Create chemicals and substances that are non-toxic; chemical products and formulations should be produced with safer chemicals.

7. Use Renewable Feedstocks

Derive chemicals from biological or renewable sources, rather than petrochemical or unsustainable plant-derived sources.

8. Avoid Chemical Derivatives

Eliminate unnecessary steps and derivatives in a chemical reaction (e.g. temporary modifications, blocking groups) to reduce reagent consumption and waste.

9. Catalysis

When possible, opt for catalysis reactions rather than stoichiometric reagents for more efficient use of materials. Catalysts are substances that speed up the rate of a chemical reaction without being used in the process; this can minimize significant amounts of waste in unused reaction by-products.

10. Maximize Atom Economy

Reducing waste at the molecular level by maximizing the number of atoms from all reagents (substances) in the final product. Atom economy is the amount of atoms in the product at the end of a chemical process. Side products from inefficient reactions have a lower atom economy and lead to more waste. 

11. Real-time Analysis for Pollution Prevention

Monitoring chemical processes and reactions in real-time can help track efficiency, and prevent accidents to reduce waste and ensure safety.

12. Safer Chemistry for Accident Prevention

Develop chemical processes that are inherently safer to perform with reduced risks, such as carrying a reduced risk for chemical accidents, explosions, and fires.


You can read more about each principle in this article by the American Chemical Society (ACS).

Examples of Green Chemistry Across Multiple Industries

Medicine: Improved synthesis for type-2 diabetes drug

The pharmaceutical industry is making strides in developing safer drugs and vaccines by moving past traditional synthetic processes that may produce toxic waste. Greener alternatives have been shown to be cost-effective, have less side-effects, and increase efficiency. One example is Merck and Codexis’ development of a new synthesis technique for sitaglipin (Januvia™), a type 2 diabetes drug. They used enzymes (biocatalysts) to change the synthesis process, which resulted in reduced waste, higher yields, and reduced safety risks for consumers.

Material Science: Alternative biodegradable plastics for packaging

Many companies are moving towards creating renewable bioplastics. For example, the company NatureWorks is developing food containers containing polylactic acid, a type of polymer derived from renewable sources. This material can be as strong as the petroleum-based plastics used in plastic water bottles, without depending on non-renewable resources for its production.

Polylactic Acid (PLA) is considered to be a more sustainable alternative to Polyethylene Terephthalate (PET) plastic as it is derived from renewable resources, has a lower carbon footprint, and is more biodegradable. Image Credit: BioPak.

Green Chemistry is needed in the Personal Care and Cosmetic Industry

Everyday products like soap, shampoo, and cream are used extensively throughout the world, however most carry an underappreciated environmental footprint in both their production and use. These personal care products have raised concerns due to the nature of the harmful pollutants they emit as well as the risks of bioaccumulation that result from these substances. The chemicals hidden in our soaps, shampoos and cosmetics are washed away into the environment, posing a health risk to the species that inhabit the region. The detection of these chemicals has made it harder for wastewater treatment facilities and microbes to remove and filter these substances. Many synthetic detergents and surfactants are non-biodegradable, carry toxicity risks to aquatic wildlife, and can disrupt the water cycle by affecting water oxygenation. Opportunities for green chemistry to improve safety and sustainability of personal care products and their production can be found throughout the industry.

Sunscreen

Sunscreen can protect our skin from solar UV radiation, which is either organic (containing chemicals that filter or absorb UV light) or inorganic (containing metal oxides that absorb UV light). However, the active chemicals in organic sunscreens are considered an emerging pollutant as they are increasingly present in the aquatic environment (rivers and streams). These contaminating UV-filters include Ethylhexyl Methoxycinnamate (EHMC), Octocrylene (OC), and Butyl Methoxydibenzoylmethane (BMDM).

Soaps

Soaps help remove excess dirt and oil from our skin that water cannot accomplish alone. These products are an integral part of our daily routine, however many soap products carry significant sustainability concerns. Synthetic surfactants like sodium laureth sulfate (SLES) are often used in these products, which are predominantly derived from either petroleum or palm-oil and are created through successive chemical reactions in their synthesis. This synthesis process can also result in the production of a by-product 1,4-dioxane, which doesn’t readily break down in aquatic environments and has been classified as a potential carcinogen.

Skin Moisturizer

Moisturizers are water-based lotions, creams, and gels used to smooth our skin and enhance skin luminosity. Unfortunately, harmful chemicals are often found in these products, such as sulfates and parabens. Sulfates, similar to surfactants, are petroleum and plant-derived and can irritate the human skin and eyes. Parabens function as preservatives and are found in many personal care products (like surfactants), however they are environmental toxins that can disrupt aquatic ecosystems and damage aquatic wildlife. 


References and Further Reading

  • Agbenyega, J. (2021, July 27). Sustainable Chemistry in the Pharma Industry: Greener Pastures for those who innovate. CAS. Retrieved October 4, 2021. Link.
  • Environmental Protection Agency. (2020, December 18). Basics of Green Chemistry. EPA. Retrieved October 7, 2021. Link.
  • Hogue, C. (2020, November 8). 1,4-Dioxane: Another forever chemical plagues drinking-water utilities. Cen.acs.org. Retrieved October 7, 2021. Link.
  • Johnson, P., Trybala, A., Starov, V., & Pinfield, V. J. (2020). Effect of synthetic surfactants on the environment and the potential for substitution by biosurfactants. Advances in Colloid and Interface Science, 288. Link.
  • Taylor, P. (2012, January 5). FDA approves Greener Process for Januvia Production. Pharmafile. Retrieved October 7, 2021. Link.
  • Why is Green Chemistry Important? Zymvol. (2021, September 22). Retrieved October 7, 2021. Link.
  • 12 Principles of Green Chemistry. American Chemical Society. (n.d.). Retrieved October 7, 2021. Link.