Green chemistry
Green chemistry, similar to sustainable chemistry or circular chemistry,[1] is an area of chemistry and chemical engineering focused on the design of products and processes that minimize or eliminate the use and generation of hazardous substances.[2] While environmental chemistry focuses on the effects of polluting chemicals on nature, green chemistry focuses on the environmental impact of chemistry, including lowering consumption of nonrenewable resources and technological approaches for preventing pollution.[3][4][5][6][7][8]
The overarching goals of green chemistry—namely, more resource-efficient and inherently safer design of molecules, materials, products, and processes—can be pursued in a wide range of contexts.
Green chemistry (sustainable chemistry): Design of chemical products and processes that minimize or eliminate the use or generation of substances hazardous to humans, animals, plants, and the environment. Note 1: Modified from ref.[9] to be more general.
Note 2: Green chemistry discusses the engineering concept of pollution prevention and zero waste both at laboratory and industrial scales. It encourages the use of economical and ecocompatible techniques that not only improve the yield but also bring down the cost of disposal of wastes at the end of a chemical process.[10]
History
Green chemistry emerged from a variety of existing ideas and research efforts (such as atom economy and catalysis) in the period leading up to the 1990s, in the context of increasing attention to problems of chemical pollution and resource depletion. The development of green chemistry in Europe and the United States was linked to a shift in environmental problem-solving strategies: a movement from command and control regulation and mandated lowering of industrial emissions at the "end of the pipe," toward the active prevention of pollution through the innovative design of production technologies themselves. The set of concepts now recognized as green chemistry coalesced in the mid- to late-1990s, along with broader adoption of the term (which prevailed over competing terms such as "clean" and "sustainable" chemistry).[11][12]
In the United States, the Environmental Protection Agency played a significant early role in fostering green chemistry through its pollution prevention programs, funding, and professional coordination. At the same time in the United Kingdom, researchers at the University of York contributed to the establishment of the Green Chemistry Network within the Royal Society of Chemistry, and the launch of the journal Green Chemistry.[12]
Principles
In 1998, Paul Anastas (who then directed the Green Chemistry Program at the US EPA) and John C. Warner (then of Polaroid Corporation) published a set of principles to guide the practice of green chemistry.[13] The twelve principles address a range of ways to lower the environmental and health impacts of chemical production, and also indicate research priorities for the development of green chemistry technologies.
The principles cover such concepts as:
- the design of processes to maximize the amount of raw material that ends up in the product;
- the use of renewable material feedstocks and energysources;
- the use of safe, environmentally benign substances, including solvents, whenever possible;
- the design of energy efficient processes;
- avoiding the production of waste, which is viewed as the ideal form of waste management.
The twelve principles of green chemistry are:[14]
- Prevention: Preventing waste is better than treating or cleaning up waste after it is created.
- Atom economy: Synthetic methods should try to maximize the incorporation of all materials used in the process into the final product. This means that less waste will be generated as a result.
- Less hazardous chemical syntheses: Synthetic methods should avoid using or generating substances toxic to humans and/or the environment.
- Designing safer chemicals: Chemical products should be designed to achieve their desired function while being as non-toxic as possible.
- Safer solvents and auxiliaries: Auxiliary substances should be avoided wherever possible, and as non-hazardous as possible when they must be used.
- Design for energy efficiency: Energy requirements should be minimized, and processes should be conducted at ambient temperature and pressure whenever possible.
- Use of renewable feedstocks: Whenever it is practical to do so, renewable feedstocks or raw materials are preferable to non-renewable ones.
- Reduce derivatives: Unnecessary generation of derivatives—such as the use of protecting groups—should be minimized or avoided if possible; such steps require additional reagents and may generate additional waste.
- Catalysis: Catalytic reagents that can be used in small quantities to repeat a reaction are superior to stoichiometric reagents (ones that are consumed in a reaction).
- Design for degradation: Chemical products should be designed so that they do not pollute the environment; when their function is complete, they should break down into non-harmful products.
- Real-time analysis for pollution prevention: Analytical methodologies need to be further developed to permit real-time, in-process monitoring and control before hazardous substances form.
- Inherently safer chemistry for accident prevention: Whenever possible, the substances in a process, and the forms of those substances, should be chosen to minimize risks such as explosions, fires, and accidental releases.
Trends
Attempts are being made not only to quantify the greenness of a chemical process but also to factor in other variables such as
Green chemistry is increasingly seen as a powerful tool that researchers must use to evaluate the environmental impact of nanotechnology.[16] As nano materials are developed, the environmental and human health impacts of both the products themselves and the processes to make them must be considered to ensure their long-term economic viability. There is a trend of nano material technology in the practice, however, people ignored the potential nanotoxicity. Therefore, people need to address further consideration on legal, ethical, safety, and regulatory issues associated with nanomaterials, [17]
Examples
Green solvents
The major application of solvents in human activities is in paints and coatings (46% of usage). Smaller volume applications include cleaning, de-greasing, adhesives, and in chemical synthesis.[18] Traditional solvents are often toxic or are chlorinated. Green solvents, on the other hand, are generally less harmful to health and the environment and preferably more sustainable. Ideally, solvents would be derived from renewable resources and biodegrade to innocuous, often a naturally occurring product.[19][20] However, the manufacture of solvents from biomass can be more harmful to the environment than making the same solvents from fossil fuels.[21] Thus the environmental impact of solvent manufacture must be considered when a solvent is being selected for a product or process.[22] Another factor to consider is the fate of the solvent after use. If the solvent is being used in an enclosed situation where solvent collection and recycling is feasible, then the energy cost and environmental harm associated with recycling should be considered; in such a situation water, which is energy-intensive to purify, may not be the greenest choice. On the other hand, a solvent contained in a consumer product is likely to be released into the environment upon use, and therefore the environmental impact of the solvent itself is more important than the energy cost and impact of solvent recycling; in such a case water is very likely to be a green choice. In short, the impact of the entire lifetime of the solvent, from cradle to grave (or cradle to cradle if recycled) must be considered. Thus the most comprehensive definition of a green solvent is the following: "a green solvent is the solvent that makes a product or process have the least environmental impact over its entire life cycle."[23]
By definition, then, a solvent might be green for one application (because it results in less environmental harm than any other solvent that could be used for that application) and yet not be a green solvent for a different application. A classic example is water, which is a very green solvent for consumer products such as toilet bowl cleaner but is not a green solvent for the manufacture of polytetrafluoroethylene. For the production of that polymer, the use of water as solvent requires the addition of perfluorinated surfactants which are highly persistent. Instead, supercritical carbon dioxide seems to be the greenest solvent for that application because it performs well without any surfactant.[23] In summary, no solvent can be declared to be a "green solvent" unless the declaration is limited to a specific application.
Synthetic techniques
Novel or enhanced synthetic techniques can often provide improved environmental performance or enable better adherence to the principles of green chemistry. For example, the 2005
Carbon dioxide as blowing agent
In 1996,
Hydrazine
Addressing principle #2 is the peroxide process for producing hydrazine without cogenerating salt. Hydrazine is traditionally produced by the Olin Raschig process from sodium hypochlorite (the active ingredient in many bleaches) and ammonia. The net reaction produces one equivalent of sodium chloride for every equivalent of the targeted product hydrazine:[27]
- NaOCl + 2 NH3 → H2N-NH2 + NaCl + H2O
In the greener peroxide process hydrogen peroxide is employed as the oxidant and the side product is water. The net conversion follows:
- 2 NH3 + H2O2 → H2N-NH2 + 2 H2O
Addressing principle #4, this process does not require auxiliary extracting solvents.
1,3-Propanediol
Addressing principle #7 is a green route to
is used to make new polyesters for the manufacture of carpets.Lactide
In 2002, Cargill Dow (now
Carpet tile backings
In 2003 Shaw Industries selected a combination of polyolefin resins as the base polymer of choice for EcoWorx due to the low toxicity of its feedstocks, superior adhesion properties, dimensional stability, and its ability to be recycled. The EcoWorx compound also had to be designed to be compatible with nylon carpet fiber. Although EcoWorx may be recovered from any fiber type, nylon-6 provides a significant advantage. Polyolefins are compatible with known nylon-6 depolymerization methods. PVC interferes with those processes. Nylon-6 chemistry is well-known and not addressed in first-generation production. From its inception, EcoWorx met all of the design criteria necessary to satisfy the needs of the marketplace from a performance, health, and environmental standpoint. Research indicated that separation of the fiber and backing through elutriation, grinding, and air separation proved to be the best way to recover the face and backing components, but an infrastructure for returning postconsumer EcoWorx to the elutriation process was necessary. Research also indicated that the postconsumer carpet tile had a positive economic value at the end of its useful life. EcoWorx is recognized by MBDC as a certified cradle-to-cradle design.
Transesterification of fats
In 2005,
Bio-succinic acid
In 2011, the Outstanding Green Chemistry Accomplishments by a Small Business Award went to
Laboratory chemicals
Several laboratory chemicals are controversial from the perspective of Green chemistry. The Massachusetts Institute of Technology created a "Green" Alternatives Wizard [1] to help identify alternatives. Ethidium bromide, xylene, mercury, and formaldehyde have been identified as "worst offenders" which have alternatives.[32] Solvents in particular make a large contribution to the environmental impact of chemical manufacturing and there is a growing focus on introducing Greener solvents into the earliest stage of development of these processes: laboratory-scale reaction and purification methods.[33] In the Pharmaceutical Industry, both GSK[34] and Pfizer[35] have published Solvent Selection Guides for their Drug Discovery chemists.
Legislation
The EU
In 2007, The EU put into place the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) program, which requires companies to provide data showing that their products are safe. This regulation (1907/2006) ensures not only the assessment of the chemicals' hazards as well as risks during their uses but also includes measures for banning or restricting/authorising uses of specific substances. ECHA, the EU Chemicals Agency in Helsinki, is implementing the regulation whereas the enforcement lies with the EU member states.
United States
The United States formed the Environmental Protection Agency (EPA) in 1970 to protect human and environmental health by creating and enforcing environmental regulation. Green chemistry builds on the EPA’s goals by encouraging chemists and engineers to design chemicals, processes, and products that avoid the creation of toxins and waste.[36]
The U.S. law that governs the majority of industrial chemicals (excluding pesticides, foods, and pharmaceuticals) is the
Passed in 1990, the Pollution Prevention Act helped foster new approaches for dealing with pollution by preventing environmental problems before they happen.
Green chemistry grew in popularity in the United States after the Pollution Prevention Act of 1990 was passed. This Act declared that pollution should be lowered by improving designs and products rather than treatment and disposal. These regulations encouraged chemists to reimagine pollution and research ways to limit the toxins in the atmosphere. In 1991, the EPA Office of Pollution Prevention and Toxics created a research grant program encouraging the research and recreation of chemical products and processes to limit the impact on the environment and human health.[39] The EPA hosts The Green Chemistry Challenge each year to incentivize the economic and environmental benefits of developing and utilizing green chemistry.[40]
In 2008, the State of California approved two laws aiming to encourage green chemistry, launching the California Green Chemistry Initiative. One of these statutes required California's Department of Toxic Substances Control (DTSC) to develop new regulations to prioritize "chemicals of concern" and promote the substitution of hazardous chemicals with safer alternatives. The resulting regulations took effect in 2013, initiating DTSC's Safer Consumer Products Program.[41]
Scientific journals specialized in green chemistry
- Green Chemistry (RSC)
- Green Chemistry Letters and Reviews (Open Access) (Taylor & Francis)
- Wiley)
- ACS Sustainable Chemistry & Engineering (ACS)
Contested definition
There are ambiguities in the definition of green chemistry, and in how it is understood among broader science, policy, and business communities. Even within chemistry, researchers have used the term "green chemistry" to describe a range of work independently of the framework put forward by Anastas and Warner (i.e., the 12 principles).[12] While not all uses of the term are legitimate (see greenwashing), many are, and the authoritative status of any single definition is uncertain. More broadly, the idea of green chemistry can easily be linked (or confused) with related concepts like green engineering, environmental design, or sustainability in general. The complexity and multifaceted nature of green chemistry makes it difficult to devise clear and simple metrics. As a result, "what is green" is often open to debate.[42]
Awards
Several scientific societies have created awards to encourage research in green chemistry.
- Australia's Green Chemistry Challenge Awards overseen by The Royal Australian Chemical Institute (RACI).
- The Canadian Green Chemistry Medal.[43]
- In Italy, Green Chemistry activities center around an inter-university consortium known as INCA.[44]
- In Japan, The Green & Sustainable Chemistry Network oversees the GSC awards program.[45]
- In the United Kingdom, the Green Chemical Technology Awards are given by Crystal Faraday.[46]
- In the US, the Presidential Green Chemistry Challenge Awards recognize individuals and businesses.[47][48]
See also
- Bioremediation – a technique that generally falls outside the scope of green chemistry
- Environmental engineering science
- Green Chemistry (journal) – published by the Royal Society of Chemistry
- Green chemistry metrics
- Green computing – a similar initiative in the area of computing
- Green engineering
- Substitution of dangerous chemicals
- Sustainable engineering
References
- S2CID 249357642.
- ^ "Green Chemistry". United States Environmental Protection Agency. 2006-06-28. Retrieved 2011-03-23.
- S2CID 92947071.
- PMID 22468603.
- PMID 25793239.
- PMID 21209638.
- S2CID 12340643.
- doi:10.1039/A807961G.
- .
- S2CID 98107080.
- S2CID 146774456.
- ^ .
- ISBN 9780198502340.
- ^ "12 Principles of Green Chemistry - American Chemical Society". American Chemical Society. Retrieved 2018-02-16.
- PMID 16542013.
- ^ "Green nanotechnology" (PDF). Archived from the original (PDF) on 2016-04-06. Retrieved 2008-03-01.
- OCLC 1256699945.)
{{cite book}}
: CS1 maint: location missing publisher (link - ^ Torok, Bela (2017). Green Chemistry: An Inclusive Approach. Amsterdam: Elsevier. p. Ch 3.15.
- .
- PMID 9539018.
- .
- PMID 29300087.
- ^ ISBN 9780128046777.
- ^ "The Nobel Prize in Chemistry 2005". The Nobel Foundation. Retrieved 2006-08-04.
- PMID 15795753.
- S2CID 109584470.
- .
- S2CID 137246045.
- ^ "2011 Small Business Award". United States Environmental Protection Agency. 2013-03-12.
- ^ "Succinic acid maker BioAmber is bankrupt". Chemical & Engineering News. 2018-05-13.
- ^ "Succinic acid, once a biobased chemical star, is barely being made". Chemical & Engineering News. 2019-03-20.
- ^ Coombs A. (2009). Green at the Bench Archived 2009-07-10 at the Wayback Machine. The Scientist.
- PMID 25798192.
- S2CID 56376990.
- S2CID 97175218.
- ^ "What Is Green Chemistry?". American Chemical Society. Retrieved 2021-01-29.
- S2CID 43455643.
- PMID 19672398.
- ^ "History of Green Chemistry | Center for Green Chemistry & Green Engineering at Yale". greenchemistry.yale.edu. Retrieved 2021-01-29.
- ^ US EPA, OCSPP (2013-02-13). "Information About the Green Chemistry Challenge". US EPA. Retrieved 2021-01-29.
- ^ California Department of Toxic Substances Control. "What is the Safer Consumer Products (SCP) Program?". Retrieved 5 September 2015.
- PMID 22963612.
- ^ "Announcing the 2005 Canadian Green Chemistry Medal". RSC Publishing. Retrieved 2006-08-04.
- ^ "Chemistry for the Environment". Interuniversity Consortium. Retrieved 2007-02-15.
- ^ "Green & Sustainable Chemistry Network, Japan". Green & Sustainable Chemistry Network. Archived from the original on 2001-05-13. Retrieved 2006-08-04.
- ^ "2005 Crystal Faraday Green Chemical Technology Awards". Green Chemistry Network. Archived from the original on 2002-12-17. Retrieved 2006-08-04.
- ^ "The Presidential Green Chemistry Awards". United States Environmental Protection Agency. Retrieved 2006-07-31.
- ^ "Information about the Presidential Green Chemistry Challenge". 2013-02-13. Retrieved 2014-08-10.