"Green chemistry is the design of chemical products and processes
that reduce or eliminate the use and generation of hazardous substances."

"The challenge is now set for chemists to design new chemicals based on these Principles and for companies to demand their chemical suppliers produce inherently safer chemicals."

What Exactly IS Green Chemistry?

By Beverly Thorpe

On July10th CBC News released an exposé entitled: Some ‘green’ detergents still contain chemicals. The title of this article underscores all the confusion about how the public views chemicals and how we are now supposedly defining ‘green’ chemicals. The title is so blatantly misleading that I was surprised to read it. In reality ALL products contain chemicals, the human body contains chemicals, all materials on this earth contain chemicals. To imply that plant ingredients are not chemicals is a basic and unscientific misrepresentation and also a mischaracterization of what is green chemistry. So let’s review what green chemistry means.

Green chemistry is the design of chemical products and processes that reduce or eliminate the use and generation of hazardous substances. The term came to light with the publication of a small book entitled, Green Chemistry: Theory and Practice written in 1998. In it, two US chemists, Dr John Warner and Dr Paul Anastas,outlined their Twelve Principles of Green Chemistry to demonstrate how chemical production could respect human health and the environment while also being efficient and profitable.

Many of the principles are common sense, even to a non-chemist, such as designing a molecule to be inherently safer or generate less waste in its synthesis. Why is this considered a radical approach? Because currently chemicals are typically created with the expectation that any chemical hazard can somehow be controlled or managed by establishing “safe” concentrations and exposure limits. Green chemistry aims to eliminate hazards right at the design stage. To do this a chemist must possess basic knowledge about toxicology and ecological impacts. The tragedy of our current educational system is that the chemistry curriculum does not require the study of biological sciences. This results in graduate chemists having no or little awareness about the impacts on human health and the environment of the new materials they create in the lab. Sadly, to this day, this is the norm rather than the exception. Green chemistry is considered a ‘supplemental or non compulsory’ additional course, not a mainstream approach to chemicals design.

Other Principles of Green Chemistry refer to the use of renewable feedstocks. This is where readers might be confused with the assertion that ‘plant based’ chemicals are somehow safer than petroleum based chemicals. Today’s chemical industry relies almost entirely on non-renewable petroleum as the primary building block to create chemicals. This type of chemical production is typically very energy intensive, inefficient, and toxic — and results in significant energy use, as well as generation of hazardous waste. The use of renewable materials including the use of agricultural waste or biomass can, in general, be considered less hazardous in comparison to petroleum based chemicals. However the provenance of the feedstock is important. Recently the use of palm oil has come under intense scrutiny due to its association with tropical deforestation. The type of agricultural system is important to know. Was the feedstock grown with genetically engineered crops or heavy use of toxic chemicals? Is it a food source or a non-food source of plant material? In addition it is important to also realize that it is still possible to design highly hazardous chemical formulas using bio-based feedstocks.

For example, the Solvay company in Brazil plans to make ‘Green PVC’ commonly known as vinyl, using a sugarcane based ethanol feedstock. PVC (polyvinyl chloride) is one of the most toxic plastics made. Its chlorine content generates highly toxic dioxins in the production of the monomer and the presence of chlorine in the polymer leads to the formation of chlorinated dioxins when PVC is burned. Dioxin is a well known carcinogen and has been termed the most toxic molecule ever synthesized. It is also one of the twelve POPs (persistent organic pollutants) defined by the International Stockholm Convention as a priority global pollutant targeted for phase out because of its ability to be transported and persist throughout the globe, even as far as the Arctic.

Because PVC on its own is an unstable material, it requires the further addition of hundreds of chemical additives to achieve its functional characteristics, such as plasticizers to make the polymer soft, or stabilizers and hardeners to make PVC rigid. Many phthalates (tha-lates) or softeners, are known to cause hormone disruption in animal studies and this resulted in a ban on phthalates in children’s toys. Now the PVC industry is replacing certain phthalates with safer chemicals, some of which may in fact be plant based. However the substitution of one hazardous ingredient with a safer plant based formula does not make the product itself safer – or at least not when one considers the life cycle of that material. Regardless of how many plant sourced substitute ingredients the vinyl industry publicizes, the inherently hazardous nature of PVC as a chlorinated plastic remains. And it will continue to present an increasing source of global dioxin generation. One has only to look at the expanding PVC industry in Asia to realize that our global health is linked to global production systems.

The CBC News survey of detergents mentioned the Design for Environment (DfE) program of the US Environmental Protection Agency. This program requires suppliers to have all their chemicals (bio-based or petroleum based) screened against a set of criteria that measures a chemical’s impact on human health, its inherent toxicity, and ability to persist in the environment or bio-accumulate in concentration up the food chain. The criteria go much further than simply assessing the number of plant based ingredients in the product. Of course claims that a product is ‘naturally sourced’ only to discover that 30 percent of its ingredients are petroleum based are clearly misleading. But we need to understand what impacts these chemicals have; not just where they were sourced.  Responsible manufacturers know and disclose all ingredients in their products and commit to continuous improvement by phasing out inherently hazardous chemicals and replacing them with safer substitutes. New tools such as the Green Screen for Safer Chemicals developed by Clean Production Action are helping companies to achieve this move to safer substitutes. The Green Screen assesses chemicals based on a list of 17 criteria (much like the DfE set of criteria) but it goes further than the DfE program by providing four main benchmarks for companies to chart their progress to safe chemistry. HP is now the global leader in using the Green Screen to choose safer substitutes to PVC cables and hazardous flame retardant chemicals. Other major corporations in the electronics, auto and outdoor clothing industry sectors are now screening their chemicals against the Green Screen tool because the method is scientifically rigorous and transparent. This is now an important tool in the green chemistry toolbox and although it does not differentiate a chemical based on its original feedstock, it does assign a score based on its inherent hazard. And that is why green chemistry is such an elegant, complicated concept:–it encompasses all of the Twelve Principles of Green Chemistry. The challenge is now set for chemists to design new chemicals based on these Principles and for companies to demand their chemical suppliers produce inherently safer chemicals.

Beverly Thorpe is a member of the Great Lakes Green Chemistry Advisory Board and Communications Director and Partner at Clean Production Action

The Twelve Principles of Green Chemistry*

   1. Prevention - It is better to prevent waste than to treat or clean up waste after it has been created.
   2. Atom Economy - Synthetic methods should be designed to maximize the incorporation of all   materials used in the process into the final product.
   3. Less Hazardous Chemical Syntheses - Wherever practicable, synthetic methods should be designed to use and generate substances that possess little or no toxicity to human health and the environment.
   4. Designing Safer Chemicals - Chemical products should be designed to effect their desired function while minimizing their toxicity.
   5. Safer Solvents and Auxiliaries - The use of auxiliary substances (e.g., solvents, separation agents, etc.) should be made unnecessary wherever possible and innocuous when used.
   6. Design for Energy Efficiency - Energy requirements of chemical processes should be recognized for their environmental and economic impacts and should be minimized. If possible, synthetic methods should be conducted at ambient temperature and pressure.
   7. Use of Renewable Feedstocks - A raw material or feedstock should be renewable rather than depleting whenever technically and economically practicable.
   8. Reduce Derivatives -  Unnecessary derivatization (use of blocking groups, protection/ deprotection, temporary modification of physical/chemical processes) should be minimized or avoided if possible, because such steps require additional reagents and can generate waste.
   9. Catalysis - Catalytic reagents (as selective as possible) are superior to stoichiometric reagents.
  10. 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.
  11. Real-time analysis for Pollution Prevention - Analytical methodologies need to be further developed to allow for real-time, in-process monitoring and control prior to the formation of hazardous substances.
  12. 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, explosions, and fires.

*Anastas, Paul & Warner, John. Green Chemistry: Theory and Practice (Oxford University Press: New York, 1998)

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Green Engineering

"Green Engineering is the development and commercialization of industrial processes that are economically feasible and reduce the risk to human health and the environment."

  The Twelve Principles of Green Engineering** 
 
1. Inherent Rather Than Circumstantial
      Designers need to strive to ensure that all materials and energy inputs and outputs are as inherently nonhazardous as possible.
   2. Prevention Instead of Treatment
      It is better to prevent waste than to treat or clean up waste after it is formed.
   3. Design for Separation
      Separation and purification operations should be designed to minimize energy consumption and materials use.
   4. Maximize Efficiency
      Products, processes, and systems should be designed to maximize mass, energy, space, and time efficiency.
   5. Output-Pulled Versus Input-Pushed
      Products, processes, and systems should be "output pulled" rather than "input pushed" through the use of energy and materials.
   6. Conserve Complexity
      Embedded entropy and complexity must be viewed as an investment when making design choices on recycle, reuse, or beneficial disposition.
   7. Durability Rather Than Immortality
      Targeted durability, not immortality, should be a design goal.
   8. Meet Need, Minimize Excess
      Design for unnecessary capacity or capability (e.g., "one size fits all") solutions should be considered a design flaw.
   9. Minimize Material Diversity
      Material diversity in multicomponent products should be minimized to promote disassembly and value retention.
  10. Integrate Material and Energy Flows
      Design of products, processes, and systems must include integration and interconnectivity with available energy and materials flows.
  11. Design for Commercial "Afterlife"
      Products, processes, and systems should be designed for performance in a commercial "afterlife."
  12. Renewable Rather Than Depleting
      Material and energy inputs should be renewable rather than depleting.

**Anastas, P.T., and Zimmerman, J.B., "Design through the Twelve Principles of Green Engineering", Env. Sci. and Tech., 37, 5, 94A-101A, 2003.