Principles and Practices in Sustainable Development for the Engineering and Built Environment Professions 

Unit 3 - Biomimicry/Green Chemistry

 

Lecture 12: Green Chemistry and Green Engineering In Practice: A Succinct Overview

         

The reason green chemistry is being adopted so rapidly around the world is because it is a pathway to ensuring economic and environmental prosperity. Green chemistry (and Green Engineering) are powerful because it starts at the molecular level and ultimately delivers more environmentally benign products and processes.

Paul Anastas, Founder of Green Chemistry and Green Engineering, 2001[1]

Researchers must spur public opinions and government policies toward constructing the sustainable society in the 21st century.

Ryoji Noyori, 2001 Nobel Laureate for Chemistry, 2005

 

Educational Aim

 

To show through example, explanation, and argument why the application of Green Chemistry and Green Engineering principles can make a significant contribution to sustainable development, featuring some cutting edge examples. To demonstrate that Green Chemistry and Green Engineering are no longer just ideas, they are the basis now globally for a multi-billion dollar industry.

 

Required Reading

Hargroves, K. Smith, M. and Paten, C. (2007) Engineering Sustainable Solutions Program, Critical Literacies Portfolio – Role of Engineers in Sustainable Development A, The Natural Edge Project, Australia, Unit 2 Lecture 7.

Anastas, P.T. and Warner, J. C. (1998) Green Chemistry Theory and Practice, Oxford University Press, NY.

Learning Points

There are many additional reasons to those discussed earlier as to why the application of Green Chemistry and Green Engineering principles is making such a difference, such as:

1. In the past chemists mainly optimised the percentage yield rather than the atom economy of a chemical reaction. Ideally chemical reactions would be designed to maximise incorporation of all materials used in the process into the final product to prevent such waste production.[2] Chemical synthetic approaches have been created in both industry and academia that produce far less waste (are atom efficient) while being significantly more environmentally benign.[3] Atom economy is one form of measurement to evaluate how green is a chemical process, but there are other important aspects to take into account such as energy consumption and whether pollutants are created or not.

2. Converting feedstocks to final product along the chemical synthetic pathway requires the careful selection of reagents, catalysts, solvents and reaction conditions. In the past the focus has mainly been on optimising these for percentage yield rather than atom economy. Highly efficient reactions are now a very active area of research in green chemistry is investigating alternative more benign synthetic pathways to create safer chemicals. There is significant potential to meet societies needs for chemicals without using toxic or harmful chemicals.

3. There is significant potential to reduce environmental load through reusing chemicals or recycling chemicals and plastics.[4]

4. An area of potentially significant reductions in environmental load comes from changes in the types of solvents used for reactions. Solvents are used as a medium in which to carry out a synthetic transformation in chemistry and industry. To reduce environmental impacts the chemical industry is reducing the usage of organic solvents,[5] has phased out halogenated solvents[6] and is seeking more alternatives.

5. Organic solvents still pose a major problem because they are being used in large volumes in synthesis, processing and separations. Many solvents used are classified as volatile organic compounds (VOCs) or hazardous air pollutants (HAPs) and are flammable, toxic and carcinogenic.[7] While such solvents can be recycled, they often require costly and energy-inefficient purification procedures such as distillation, and the use of the recycled products is limited to non-pharmaceutical processes such as the petrochemical and plastics industries. Increasingly, VOC’s can be replaced by non-toxic, non-volatile, recyclable and renewable solvents such as ionic liquids, water, polypropylene glycols or super-critical CO2. Supercritical CO2 offers numerous advantages as a benign solvent as it is non-toxic, non-flammable, inexpensive, and can be separated from the product by depressurisation.

6. An area of critical importance to Green Chemistry and Green Engineering is catalysis. Catalysts in nature, in lab chemistry and the chemical industry play a role of assisting to lower the activation energy barrier of a reaction, and thereby help to catalyse the chemical reaction. Thus they can assist to help create new synthetic pathways for chemical reactions that use less energy than synthetic pathways used today.

7. There are usually several possible sources of feedstocks and synthetic pathways to create any chemical. Traditionally, chemistry and the chemical industry has gone for more simple approaches such as A + B = C. Find two things to combine to get just the substance you want, and you're done. Nature uses slower but less energy- and input- intensive methods. For example, complex biomolecular machinery can take A, add B to get D, then take E, add some F, bits of G, H and I to get K, then combine D, K and a few dozen other examples of complex molecular gymnastics to finally come up with the desired C. Nature’s way is done at ambient temperature harnessing catalysts to help reagents get over the activation energy barrier of a reaction.

8. Nature already effectively runs on Green Chemistry and Green Engineering principles for all of its processes, therefore there is much that engineers can learn from nature. As the UK Chemical Leadership Council wrote,[8] ‘It is very difficult to achieve step-change improvements in environmental and economic performance through incremental improvements in conventional production technologies. For a growing number of chemical companies, inspiration is coming from biomimicry.’ (See the Case Study featured in the Brief Background Information)

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Brief Background Information

 

A succinct overview of why the application of Green Chemistry and Green Engineering Principles is already making a difference.
Green Chemistry has been able to assist industry in its drive towards sustainability by addressing issues in the design of chemical processes, namely: replacement feedstocks, alternative synthetic pathways, and alternative solvents. The burgeoning field of industrial ecology complements Green Chemistry by providing the tools and methods for measurement and evaluation for environmental auditing and impact of processes, essential for cost benefit analysis.[9]

Green Chemistry Seeks to Optimise the Atom Economy
Green Chemistry enables significant waste reduction through improved atom economy[10] (that is reacting as few reagent atoms as possible in order to reduce waste[11]). Atom economy moves the practice of minimising waste to the molecular level. Traditionally, chemists have focused on maximising percentage yield, minimising the number of steps or synthesising a completely unique chemical. The Green Chemistry principle of optimising the atom economy introduces a new goal into reaction chemistry: designing reactions so that as many as possible of the atoms present in the starting materials end up in the product rather than in the waste stream. This concept provides a framework for evaluating different chemistries, and an ideal to strive for in new reaction chemistry. For example, a chemist practicing atom economy would choose to synthesise a needed product by putting together basic building blocks, rather than by breaking down a much larger starting material and discarding most of it as waste.

Barry Trost,[12] from Stanford University, published the concept of atom economy in Science in 1991.[13] In 1998 he received the Presidential Green Chemistry Challenge Award for his work. At the award ceremony, Paul Anderson (1997 ACS President) commented, ‘By introducing the concept of ‘atom economy, Dr. Trost has begun to change the way in which chemists measure the efficiency of the reactions they design.’ Atom economy answers the basic question, ‘How much of what you put into your pot ends up in your product?’ The atom economy describes the conversion efficiency of a chemical process in terms of all atoms involved. Atom economy can be written as: % atom economy = Molecular Weight (desired products) / Molecular Weight (all reactants) x 100%.

It is very important to note that atom economy is one form of measurement to evaluate how green is a chemical reaction, but there are other important aspects to take into account such as energy consumption and whether pollutants are created or not. Other important ways Green Chemistry and Green Engineering are making a significant difference is through reduced use of toxic reagents and hazardous chemicals, and the production of environmentally benign reactions and chemical products. Synthetic strategies now employ benign solvent systems, such as ionic liquid, water[14] and supercritical fluids such as carbon dioxide.[15] Solvent free methods have also been applied, as have biphasic systems, to integrate preparation and product recovery. For example, phases of liquids that separate are going to be much easier to recover without needing an extra extractive processing step. In addition, there has been significant research on utilising high-temperature water and microwave heating, sono-chemistry (chemical reactions activated by sonic waves) and combinations of these and other enabling technologies.[16]

Another very important area of Green Chemistry is the science of catalysis. Catalytic processes have allowed the development of efficient synthetic routes which often involve significantly less energy to be used in the reaction.[17]

The 2001 Nobel Laureate for Chemistry Ryoji Noyori in a 2005 article[18] identified three key developments in Green Chemistry as being of great significance:

1. The use of supercritical carbon dioxide as a green solvent.
   
   
2. Aqueous hydrogen peroxide for clean oxidations.
   
   
3. The use of hydrogen in asymmetric synthesis.

A critical area of ongoing research is addressing the question of how can modern society meet its chemical and plastic needs from renewable feedstocks. In 1989, Szmant reported that 98 percent of organic chemicals used in the lab and by industry are derived from petroleum.[19] Hence renewable feedstocks, often combined with biomimetic methods (conventional chemical reactions that mimic nature) and biocatalysts, are under examination as alternatives to fossil carbon based starting materials. The Netherlands Sustainable Technology Development project has found that in principle there is sufficient biomass production potential to meet the demands for industrial organic chemicals after the more pressing needs to produce food have been met.[20] Such exciting results and progress provides government, industry and academia with a solid foundation from which to work together to over time truly develop sustainable chemical and plastic industries.

Green Chemistry Awards
It is important to note that, while the fields of Green Chemistry and Green Engineering are relatively new, they are growing rapidly and there are now many significant awards for Green Chemistry. The award winners listed on the Green Chemistry award’s web sites (see footnotes) offer a good overview of the many ways that chemists and chemical engineers applying Green Chemistry principles are already making a difference.

The US Presidential Green Chemistry Challenge Awards began in 1995 to recognise individual researchers.[21] Nominations are evaluated by an independent panel of chemists convened by the American Chemical Society. The Royal Australian Chemical Institute each year awards Australia’s Green Chemistry Challenge Awards.[22] In Canada, The Canadian Green Chemistry Medal[23] is awarded to an individual or group. In Italy, there are three awards given annually to industry. In Japan, The Green & Sustainable Chemistry Network,[24] formed in 1999, began their Green Chemistry awards program in 2001. In the United Kingdom, the Crystal Faraday Partnership,[25] a non-profit group founded in 2001, began their Green Chemistry awards in 2004.

The Nobel Prize Committee acknowledged the importance of Green Chemistry in 2005 by awarding the Nobel Prize for Chemistry for ‘the development of the metathesis method in organic synthesis’ to Yves Chauvin, Robert H. Grubbs, and Richard R. Schrock. The Nobel Prize Committee wrote that,

This represents a great step forward for 'green chemistry', reducing potentially hazardous waste through smarter production. Metathesis is an example of how important basic science has been applied for the benefit of man, society and the environment.

Table 12.1 presents a selection of award winners from the USA Presidential Green Chemistry Award to give an idea of the breadth of innovation for sustainability occurring in this important new field.

Company	Sample of USA Presidential Green Chemistry Awards
Professor Galen J. Suppes, from the University of Missouri-Columbia 2006 Academic Award	For the invention of a system of converting waste glycerine from bio-diesel production to propylene glycol. Professor Suppes enabled conversion to occur at a significantly lower temperature using a copper-chromite catalyst, while raising the efficiency of the distillation reaction. Propylene glycol produced through this method is cost competitive enough to replace the more toxic ethylene glycol, the primary ingredient in automobile anti-freeze.[26]
Archer Daniels Midland Company (ADM) and Novozymes 2005 Greener Synthetic Pathways Award	Medical research has shown the negative effects on human health of Trans-fats. Novozymes and ADM have worked together to develop techniques that do not create Trans-fats. They have developed a new green process for the interesterification of oils and fats which interchanges saturated and unsaturated fatty acids without producing Trans-fats. As well as providing significant health benefits the process has greatly improved the atom economy, reduced the use of toxic chemicals and water, and waste by-products.[27]
Engelhard Organic Pigments 2004 Designing Safer Chemicals Award	Red, orange and yellow pigments historically were created using toxic heavy metals such as lead, chromium and cadmium. Engelhard developed environmentally friendly ‘Rightfit’ pigments for use in packaging. The company will entirely phase out its use of heavy metals. In addition, a water-based manufacturing process was used rather than the organic solvents usually associated with the creation of pigments.[28]
Bristol-Myers Squibb Co. 2004 Alternative Synthetic Pathways Award	The anti-cancer drug Taxol was first isolated from the bark of the Pacific yew tree, but isolating it required stripping the bark from the trees, killing them in the process. In addition, producing the drug took more than 20 chemical steps requiring some 20 solvents and reagents. Bristol-Myers Squibb developed a way to grow cell lines from yew trees in large fermentation tanks using only water, sugars, vitamins and trace elements. During its first five years, the process is expected to eliminate an estimated 32 metric tons of hazardous chemicals and other materials.[29]
Buckman Laboratories International 2004 Alternative Solvents/Reaction Conditions Award	One-half of the paper and paperboard currently used in the USA is recycled, but adhesives, coatings, plastics and other materials on the old paper can produce spots and holes in the new paper. Called ‘stickies’, they cost the industry US$500 million annually. Buckman uses a new enzyme to turn stickies into a water-soluble, non-sticky material. The enzyme is produced by a bacteria and is completely bio degradable. Since 2002, more than 40 paper mills have converted to the enzyme.[30]

Table 12.1. A taste of what is possible through applying Green Chemistry and Green Engineering principles
Source: US EPA[31]

Feature Case Study: Biomimicry: Inspiring Green Chemistry - Baxenden[32]
For a growing number of chemical companies, inspiration is coming from Biomimicry and the application of industrial biotechnology. UK-based Baxenden Chemicals is one of those companies. It has self-funded the development of novel polymerisation technology based on the knowledge that enzymes are nature’s catalysts. It now produces a range of polyesters of various molecular weights on a large scale using an enzyme-based bioprocess. This process saves energy, improves product quality and operates at lower cost to improve bottom line performance. Traditional methods for manufacturing polyesters require the use of titanium or tin based catalysts and temperatures above 230ºC. Baxenden’s process eliminates the potentially toxic catalysts and operates at lower process temperatures, thereby reducing energy input. The polymer arising from the bioprocess has a very uniform molecular structure and has given Baxenden a competitive advantage in a number of specialised markets.

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Key References

- Green Chemistry Institute (n.d.) Overview of the field of Green Chemistry. Available at . Accessed 5 January 2007.

- McDonough, W. and Braungart, M. (2002) Cradle to Cradle: Remaking the Way We Make Things, North Point Press. San Francisco.

- Green Chemistry Network (n.d.) Atom Efficiency PowerPoint presentation. Available at http://www.chemsoc.org/pdf/gcn/atomeff.ppt. Accessed 5 January 2007.

- Ritter, S.K. (2002) ’Green Chemistry Gets Greener’, Chemical and Engineering News, 2002, vol 80, pp 38-42. Available at http://pubs.acs.org/cen/coverstory/8020/8020green.html. Accessed 5 January 2007.

- Ritter, S.K. (2001) ’Green Chemistry’, Chemical and Engineering News, 2001, vol 79, pp 27-34. Available at http://pubs.acs.org/cen/coverstory/7929/7929greenchemistry.html. Accessed 5 January 2007.

- The Royal Australian Green Chemistry Institute Inc. (n.d.) Australia’s Green Chemistry Challenge Awards. Available at http://www.raci.org.au/national/awards/greenchemistry.html. Accessed 5 January 2007.

- Canadian Green Chemistry Network (n.d.) Homepage. Available at http://www.greenchemistry.ca/. Accessed 5 January 2007.

- The Green & Sustainable Chemistry Network (n.d.) Awards. Available at http://www.gscn.net/awardsE/index.html. Accessed 5 January 2007.

- The Green Chemistry Network (n.d.) 2005 Crystal Faraday Green Chemical Technology Awards. Available at http://www.chemsoc.org/networks/gcn/awards.htm. Accessed January 2007.

- US EPA (n.d.) Presidential Green Chemistry Challenge 1996-2006. Accessed 5 January 2007.

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[1] Ritter, S.K. (2001) ‘Green Chemistry’, cover story, Chemical and Engineering News, July 16, 2001, vol 79, no. 29. Available at http://pubs.acs.org/cen/coverstory/7929/7929greenchemistry.html. Accessed 5 January 2007. (Back)

[2] Anastas, P.T. and Warner, J. C. (1998) Green Chemistry Theory and Practice, Oxford University Press, NY. (Back)

[3] For a good example comes from Pharmacia (formerly Mosanto company) see US EPA Presidential Green Chemistry Award (1996) 1996 Greener Synthetic Pathways Award: The catalytic dehyrogenation of diethanolamine, at http://www.epa.gov/greenchemistry/pubs/pgcc/winners/gspa96.html. Accessed 5 January 2007. (Back)

[4] McDonough, W. and Braungart, M. (1998) ‘The NEXT Industrial Revolution’, The Atlantic Monthly, 1998 (October), pp 82-92; Graedel, T. (1999) ‘Green Chemistry in an industrial ecology context’, Green Chemistry, 1999, no. 1, G126 - G128. (Back)

[5] Illman, D. (1994) ‘Environmentally Benign Chemistry Aims for Processes that Don’t Pollute’, Chemical Engineering News, Sept 5, pp 22-7. (Back)

[6] Key, R.D., Howell, R.D. and Criddle, C.S. (1997) ‘Fluorinated Organics in the Biosphere’, Enviro Sci. Technol, no.31, p 2445. (Back)

[7] Anastas, P.T. and Kirchhoff, M. (2002) ‘Origins, Current Status, and Future Challenges of Green Chemistry’, Accounts of Chemical Research, vol 35, no.9, pp 686-694. (Back)

[8] Forum for the Future & Chemistry Leadership Council (2005) A vision for the sustainable production & use of chemicals, on behalf of the Chemistry Leadership Council. Available at http://www.chemistry.org.uk/pages/8/press/9308_chemistry.pdf. Accessed 5 January 2007. (Back)

[9] Strauss, C. and Scott, J. (2001) ‘The Future Re-Written’, Chemistry & Industry, Oct, 2001. (Back)

[10] Trost, B.M. (1995) ‘Atom Economy: A Challenge for Organic Synthesis - Homogeneous Catalysis Leads the Way’, Angew Chem. Int. Ed. Engl., vol 34, p 259. (Back)

[11] Green Chemistry Network (n.d.) Atom Efficiency PowerPoint presentation. Available at http://www.chemsoc.org/pdf/gcn/atomeff.ppt. Accessed 5 January 2007. (Back)

[12] Barry Trost (n.d.) About Barry Trost. Available at www.stanford.edu/group/bmtrost/bmt.html. Accessed 5 January 2007. (Back)

[13] Trost, B. (1991) ‘The Atom Economy: A Search for Synthetic Efficiency’, Science, no. 254, p 1471. (Back)

[14] Breslow, R. (1998) ‘Water as a solvent for chemical reactions’, in Anastas, P.T. and Williamson, T.C. (eds) (1998) Green Chemistry: Frontiers in Benign Chemical Syntheses and Processes, Oxford University Press, New York, chap 13; Li, C.J. (2000) ‘Water as Solvent for Organic and Material Synthesis’ in Anastas, P.T., Heine, L.G. and Williamson, T.C. (eds) (2000) Green Chemical Syntheses and Processes, American Chemical Society, Washington D.C., chap 6. (Back)

[15] Hancu, D., Powell, C. and Beckma, E.J. (2001) ‘Combined Reaction-Separation Processes in CO2’, in Anastas, P.T. Heine, L.G. and Williamson, T.C. (eds) (2001) Green Engineering, American Chemical Society, Washington, D.C., chap 7. (Back)

[16] Strauss, C.R (1999), ‘Invited Review: A Combinatorial Approach to the Development of Environmentally Benign Organic Chemical Preparations’, Australian Journal of Chemistry, no. 52, pp 83-96. (Back)

[17] Ibid. (Back)

[18] Noyori, R. (2005) ‘Pursuing Practical Elegance in Chemical Synthesis’, Chemical Communications, no. 14, pp 1807-1811. (Back)

[19] Szmant, H.H. (1989) Organic Building Clocks of the Chemical Industry, Wiley, New York, p 4. (Back)

[20] Okkerse, C. and van Bekkum, H. (1996) ‘Renewable Raw Materials for the Chemicals Industry’, Sustainability and Chemistry, Sustainable Technology Development Project, Delft, Netherlands. (Back)

[21] US EPA (n.d.) Presidential Green Chemistry Challenge. Available at http://www.epa.gov/greenchemistry/pubs/pgcc/presgcc.html. Accessed 5 January 2007. (Back)

[22] The Royal Australian Green Chemistry Institute (n.d.) Australia’s Green Chemistry Challenge Awards. Available at http://www.raci.org.au/national/awards/greenchemistry.html. Accessed 5 January 2007. (Back)

[23] Canadian Green Chemistry Network (n.d.) CGCN Homepage. Available at http://www.greenchemistry.ca/. Accessed 5 January 2007. (Back)

[24] The Green & Sustainable Chemistry Network (n.d.) Awards. Available at http://www.gscn.net/awardsE/index.html. Accessed 5 January 2007. (Back)

[25] Green Chemistry Network (n.d.) 2005 Crystal Faraday Green Chemical Technology Awards. Available at http://www.chemsoc.org/networks/gcn/awards.htm. Accessed 5 January 2007. (Back)

[26] US EPA (n.d.) 2006 USA Presidential Green Chemistry Challenge. Available at http://www.epa.gov/greenchemistry/pubs/pgcc/past.html. Accessed 5 January 2007. (Back)

[27] US EPA (n.d.) Presidential Green Chemistry Challenge 1996-2006. Available at http://www.epa.gov/greenchemistry/pubs/pgcc/presgcc.html. Accessed 5 January 2007. (Back)

[28] US EPA (n.d.) 2004 Presidential Green Chemistry Challenge. Available at http://www.epa.gov/greenchemistry/pubs/pgcc/past.html#2004. Accessed 5 January 2007. (Back)

[29] Ibid. (Back)

[30] Ibid. (Back)

[31] US EPA (n.d.) Presidential Green Chemistry Challenge 1996-2006. Available at http://www.epa.gov/greenchemistry/pubs/pgcc/presgcc.html. Accessed 5 January 2007. (Back)

[32] Extract taken from Forum for the Future and Chemistry Leadership Council (2005) A vision for the sustainable production & use of chemicals, on behalf of the Chemistry Leadership Council. Available at http://www.chemistry.org.uk/pages/8/press/9308_chemistry.pdf. Accessed 5 January 2007. (Back)

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