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Green Chemistry and Engineering: Towards a Sustainable Future
A white paper reporting on the green chemistry philosophy of reducing waste, toxicity and hazards, and its application on an industrial scale.
Green Chemistry and Engineering: Towards a Sustainable Future 1
Green Chemistry and Engineering: Towards a Sustainable Future
Table of ConTenTs
I. Executive Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
II. What Does It Mean to be Green? . . . . . . . . . . . . . . . . . . . . . . 3
III. Designing Safer Syntheses . . . . . . . . . . . . . . . . . . . . . . . . 7
IV. Reducing Toxicity by Design . . . . . . . . . . . . . . . . . . . . . . . 11
V. Renewable Feedstocks . . . . . . . . . . . . . . . . . . . . . . . . . 13
VI. Green Chemistry in Industry . . . . . . . . . . . . . . . . . . . . . . . 15
VII. Education . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
VIII. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
IX. Works Cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
X. Appendix A: The 12 Principles of Green Chemistry . . . . . . . . . . . . . . 26
XI. Appendix B: The 12 Principles of Green Engineering . . . . . . . . . . . . . 27
abouT This RepoRTThis special report is for exclusive use by members of the American Chemical Society . It is not
intended for sale or distribution by any persons or entities . Nor is it intended to endorse any
product, process, organization, or course of action . This report is for information purposes only .
© 2013 American Chemical Society
abouT The auThoRMelissae Fellet has written about chemistry for New Scientist, Chemical & Engineering News
and Chemistry World . She graduated from the Science Communication program at the
University of California, Santa Cruz and holds a Ph .D . in chemistry from Washington
University in St . Louis .
Green Chemistry and Engineering: Towards a Sustainable Future2 Green Chemistry and Engineering: Towards a Sustainable Future
I . Executive Summary
The slogan “benign by design” summarizes the ethos of green chemistry, and 12 principles
guide its implementation . In short, the main goals and applications of green chemistry are
to reduce environmental, human health and safety risks of chemicals by redesigning toxic
molecules, synthetic routes, and industrial processes .
Green chemistry is an interdisciplinary field, drawing on knowledge from chemistry,
chemical engineering, toxicology, and ecology . Chemists can design new catalysts that
reduce the amount of reagents used and thus reduce the amount of waste generated in
reactions . Chemical engineers can design a production line to recycle certain reagents and
minimize energy consumption . Toxicologists and ecologists provide information about the
toxic characteristics and effects of molecules so that chemists can then work to design new
molecules that avoid structures linked to toxicity .
Green chemistry researchers develop new catalysts, test new solvents, and experiment
with microscale flow processes . Some of this research is adopted by the chemical industry,
particularly in pharmaceuticals . Through annual green chemistry awards, the American
Chemical Society and the U .S . Environmental Protection Agency reward successful applications
of green chemistry in industry . The Royal Society of Chemistry in the United Kingdom offers a
green chemistry award every two years .
Educating future chemists is also an important part of the philosophy of green chemistry .
Green chemistry experiments, with their low-risk ingredients and connection to sustainability,
can be used as demonstrations for school groups . Green chemistry experiments are working
their way into undergraduate teaching laboratories as well . And as the next generation of
chemists learns these principles, perhaps one day green chemistry will not be an additional
consideration when designing a synthetic route or industrial process . It might just be how
things are done .
Green Chemistry and Engineering: Towards a Sustainable Future 3Green Chemistry and Engineering: Towards a Sustainable Future
II . What Does It Mean To Be Green?
The 12 principles of green chemistry (see Appendix A), outlined in 1998, ask chemists to
prevent waste, minimize energy use, use renewable raw materials, design biodegradable
products, and choose chemicals to minimize potential accidents .(1) But putting those
principles into practice often requires trade-offs, especially when you’re trying to determine the
“greenness” of an entire process .
For example, a reaction with a hazardous reagent is not attractive for a process scale because of
the inherent safety risks . But sometimes using such a reagent can shorten a reaction sequence,
reducing costs, waste and solvent use . Jeffrey V . Mitten of Novasep, a company that specializes
in chemical process development, described how the company handled this situation when
converting a hydroxyester to an aminoalcohol using diborane gas, which can ignite in humid
air .(2) Novasep’s chemists and engineers created a way to generate diborane on site and
meter it into the reaction . With the hazards contained, this route eliminated protection and
deprotection steps, shortening a five-step sequence to two steps . By using this new route, costs
were reduced by 60%, and the product yield was improved from 59% to 81% .(2)
Hazardous, But Greener
Novasep’s route to aminoalcohols defies green chemistry principles by using
hazardous diborane gas as a reagent . The process makes up for the transgression by
reducing the reaction to two steps, generating less waste, and reducing costs .
Z ORHO
O
PGZ ORPGO
O
Initial process:
Z OHPGO
Z OMs PGOMsCl – PG
Z NH
PGOR NH2 R
Z NH
HOR
Z ORHO
O O
Greener process:
B2H6R NH2
Z = CH2, NH, O, or S; PG = protecting group; Ms = methanesulfonyl
Z NH
HOR
Z NH
HOR
Green Chemistry and Engineering: Towards a Sustainable Future4 Green Chemistry and Engineering: Towards a Sustainable Future
Green metrics seek to quantify the abstract concept of sustainability .(3) These measurements
can help scientists compare processes for their overall “greenness,” although trade-offs exist
here as well . Optimizing a process for environmental effect might reduce its safety, for
example . One easily calculated metric is the E-factor, which is the mass of waste per mass of
product . This ratio, typically up to 100 for pharmaceuticals(4), reflects the amount of waste
generated in a process . In contrast, petrochemicals have an E-factor around 0 .1, near the ideal
waste-free value of zero .(2)
There’s also a need for qualitative metrics too . “You could have an E-factor of 20, which would
be low by pharmaceutical standards, but if the solvent in every single step in the process
is benzene, it’s not a green process,” Berkeley W . Cue Jr ., chair of the ACS Green Chemistry
Institute Governing Board, told Chemical & Engineering News in 2012 .(4) Many pharmaceutical
companies use a different green metric: process mass intensity (PMI) . This value reflects the
total mass of material in a process per mass of product . The ideal PMI is 1, indicating that all
reagents are converted into product . It provides a broader indication of process efficiency than
just tracking waste using the E-factor .
However, any single metric cannot describe the range of factors — from sources of raw
materials to energy use and water consumption — that affect sustainability of a particular
process . Thus, the ACS Green Chemistry Institute spearheaded the Greener Chemical Products
& Processes Standard to develop common measurements that chemists, consumers, and
policymakers can use to evaluate the environmental aspects of a particular product .(5)
“Ecolabels” on cleaners also attempt to describe sustainability . But these labels, or ingredient
lists ranked by toxicity, are not as comprehensive as the proposed standards . Industry trade
groups or environmental groups often develop the current ecolabels and product guides .
Though the rankings may reflect products with reduced toxicity, they may not account for
other sources of environmental damage, like using water and energy when washing clothes or
dishes .(6)
Green Chemistry and Engineering: Towards a Sustainable Future 5Green Chemistry and Engineering: Towards a Sustainable Future
Environmental life cycle assessment (LCA) tracks the environmental impact of a product from
the origin of its raw materials through its production, distribution, use, and disposal . Such
an analysis allows scientists to identify destructive points in the life cycle and make changes
to stem the damage . Early LCAs in the 1970s looked at ingredients, emissions, and waste
produced by different beverage containers .(7) Now a variety of analyses allows scientists
to estimate a range of potential ecological consequences, like global warming, nutrient
overloading, or environmental toxicity . Other analyses track product resource use and human
toxicity of a particular process .
These analyses provide a view of the environmental impacts and trade-offs of a particular
process that is more accurate than just looking at a single metric, such as waste . That’s because
an LCA inherently accounts for the connections between different steps of production,
distribution, and utilization . Collecting enough data about a particular process can be time-
consuming and expensive . And the methods of data collection, any models used, and any
assumptions employed in an LCA need to be known before an organization changes its policies
based on information in the analysis .(8)
There are several ways to analyze a product over its life cycle without doing a full LCA . Process
mass intensity (PMI), a common green metric, can be used to quickly estimate life cycle
impacts, as it correlates with global warming potential for compounds under development
at the pharmaceutical company GlaxoSmithKline(GSK) .(9) Chemists at GSK have also
developed several specific LCA tools . One allows for quick comparisons of synthetic routes
from experimental stages through to manufacturing .(11) Another combines this streamlined
LCA tool with a PMI calculator developed by Merck to be a standard quick LCA for the
pharmaceutical industry .(12)
An online resource, iSustain .com, helps scientists and students quickly estimate how a product
fits with the 12 principles of green chemistry .(10) Users input information about the materials
that enter a process and the waste that comes out . The site generates a Green Chemistry Index
rating that reflects a quick snapshot of process efficiency, without doing a full LCA .
CRadle-To-CRadle design The cradle-to-cradle engineering philosophy involves considering the life cycle of a product,
from raw material to disposal .(13) Industrial and academic labs that add this framework to the
12 principles of green engineering (see Appendix B) build biodegradable, renewable products
that require less energy for production . Recyclable carpet tiles are one practical application
resulting from this union .(14) Carpet fibers are often made of recyclable nylon 6, while the
backing is commonly made from rigid polyvinylchloride plastics . In 1996, Shaw Industries
started to redesign the backing to be made from a recyclable polymer as well, primarily a
low-density polyethylene . The new backing composition also created carpet tiles with better
flame-retardant characteristics than traditional carpet treated with arsenic or aluminum oxides .
The new tiles are fully recyclable, once the fibers are separated from the backing, and building
Green Chemistry and Engineering: Towards a Sustainable Future6 Green Chemistry and Engineering: Towards a Sustainable Future
blocks of each polymer can be used to make new carpet
tiles . The product won a U .S . Environmental Protection
Agency (EPA) Presidential Green Chemistry Challenge
Award for Designing Greener Chemicals in 2003 . To
encourage their customers to recycle the tile, the company
also provides free collection and recycling of used tiles .
Along with carpet, plastics are another major component
of landfills . Polylactic acid (PLA) plastics made from corn
are the leading biorenewable plastics, but breaking
them down requires high temperatures and agitation at
commercial composting sites . Plastic that isn’t recycled or
deposited in a landfill washes out to sea and disintegrates
into tiny pieces that harm wildlife . The X Prize Foundation
is developing a project challenging researchers to create
plastics that degrade in the ocean .
A researcher at the University of Florida is already working
on building plastics that break down in water . He has
designed a new way to make plastic that installs an
acid-sensitive functional group, an acetal, throughout
a polydecylene plastic made from a fatty acid in castor
seeds .(15) Plastics made with this method degrade faster
than PLA plastics in acidic tetrahydrofuran solution, a
preliminary test for water degradability . However, these
materials are still too soft to replace current PLA plastics .
five easy Things you Can do To Make youR lab MoRe susTainable
A certification program at the University of Michigan recognizes laboratory efforts to become more sustainable . At the request of the manager or head of the lab, a staff member from the university’s Office of Campus Sustainability visits the lab and provides recommendations for sustainable practices based on green chemistry principles, waste reduction, and pollution prevention . Sudhakar Reddy, the program’s coordinator, says 45 labs have participated in the program as of March 2013 . He shares a few recommendations encouraged by the program:
1 . Close fume hoods when not in use to reduce energy use .
2 . Run experiments on the microscale to reduce waste .
3 . Switch to green solvents: Use 2-methyl tetrahydrofuran in place of methylene chloride, and use cyclopentylmethyl ether in place of tetrahydrofuran, 1,4-dioxane and ether .
4 . Neutralize basic phosphate-buffered HPLC waste or acidic HCl waste to pH 7 and pour down the drain .
5 . Recycle electronics, ice packs, packaging materials, toner cartridges, pipette tip boxes, and water purification cartridges .
For more information on the program, check out the ACS GCI Nexus blog:
https://communities .acs .org/community/science/sustainability/green-chemistry-nexus-blog/blog/2013/01/10/university-of-michigan-sustainable-laboratories-recognition-program
Green Chemistry and Engineering: Towards a Sustainable Future 7Green Chemistry and Engineering: Towards a Sustainable Future
III . Designing Safer Syntheses
Chemists design safer syntheses by looking for ways to reduce waste from solvents and added
reagents . Minimizing reagent hazards and toxicity by running reactions on a small, continuous
process is also another way to reduce risk . One classic green synthesis is a route to ibuprofen
developed by the BHC Company (now BASF) in 1991 and put into industrial production the
next year .(15) This new route condensed a six-step stoichiometric synthesis to a three-step
catalytic sequence . This revamped synthesis won the EPA Presidential Green Chemistry
Challenge Award for Greener Synthetic Pathways in 1997 . This synthesis reduces waste in
several ways . About 80% of the atoms in all the reactants end up in the final product, compared
to less than 40% in the original synthesis . This increased atom economy inherently reduces
reactant waste, as more of the reagents are converted to product . Additionally, all the catalysts
in the synthesis — hydrofluoric acid and palladium — are recovered and recycled . No other
solvent besides HF is needed .
This section will discuss concepts in four areas of green chemistry research — catalysis,
solvents, alternative energy sources for reactions, and continuous processing — and show how
these ideas are reaching industry .
CaTalysisCatalysis dominates the literature on green synthesis (17), even though it’s an important
research area in its own right . The goals of catalyst development dovetail with the principles
of green chemistry: Chemists want to build a fast, long-lived, and highly selective catalyst that
works under mild conditions . Since a catalyst regenerates itself after a reaction, one molecule
of catalyst can perform several transformations . That allows scientists to get high yields from a
reaction that uses only a relatively small amount of catalyst .
Traditionally, transition metals like palladium, platinum, and ruthenium are used to build catalysts
for carbon-carbon bond-forming reactions . However, these metals are expensive and in low
abundances in the Earth’s crust . In some cases, the catalysts require large ligands to control the
selectivity of a reaction, which can be considered wasteful according to the 12 principles .
Therefore, researchers look to get the same functionality of these catalysts with a more
available and sustainable metal: iron . Iron catalysts can carry out a wide range of cross-
coupling reactions, but many of those reactions require flammable Grignard reagents .(18)
Currently, that requirement may prompt researchers to avoid using these catalysts on larger
scales until more is understood about how they work . Another iron catalyst can make an
alkylsilane used in shampoo and to soften denim with greater activity and selectivity than
industrial platinum catalysts .(19)
Green Chemistry and Engineering: Towards a Sustainable Future8 Green Chemistry and Engineering: Towards a Sustainable Future
Another independent area of research, nanoscience,
might provide insights into building green metal catalysts
too . Gold-palladium nanocatalysts can generate hydrogen
peroxide, an acceptable oxidant for green chemistry, from
hydrogen and oxygen .(20) Attaching catalysts to magnetic
nanoparticles makes it easy for chemists to separate and
recycle the catalyst after a reaction .
Other types of catalysts can reduce safety risks . Acid
catalysts attached to silica, for example, reduce
the aqueous waste generated by quenching and
neutralizing a reaction .(21) Phase transfer catalysts (often
ammonium salts) carry an insoluble reactant between
the organic and aqueous phases in a mixture . Chemists
used tetrabutylammonium bromide to catalyze the
displacement of a chloride by a cyanide ion on a process
scale . The reaction releases heat, but the researchers could
control the exotherm and prevent a temperature spike just
by controlling the stirring speed .(22)
Enzymes are commonly used as catalysts in industry,
particularly pharmaceuticals, because they work at
ambient temperatures and pressures in water .(2) That
makes them safe to handle on a process scale . One
example is the three-step enzymatic route to the key
chiral building block used to make the active ingredient
in the cholesterol-lowering drug Lipitor . The process won
enzyme company Codexis an EPA Presidential Green
Chemistry Challenge Award in 2006 . Previous routes to
the key intermediate involved separating enantiomers
in the first step (at 50% maximum yield) and a final step
plagued with byproducts . The enzymatic process gives the
desired intermediate in a greater than 90% isolated yield .
(23) The overall process has an E-factor about five times
smaller than a typical pharmaceutical designed with green
chemistry principles .
But in practice, biocatalysts are not necessarily “greener”
than chemical catalysts . A streamlined LCA comparing a
metal catalyst to an enzymatic reduction of a ketoester
revealed that some of the processes and reaction
ReCyCling and ReplaCing RaRe eaRTh eleMenTs
Much of modern technology contains rare earth elements . Magnets in wind turbines, medical imagers and hard disk drives contain terbium, neodymium, and praseodymium . So do the nickel metal hydride batteries of hybrid cars . Light emitting diodes and energy efficient fluorescent light bulbs contain europium and ytterbium .
The big issue with rare earth elements is not their suggested scarcity . These 17 elements are moderately abundant in the Earth’s crust, though they are too dispersed for extraction to be economically efficient .(1) Most of the easily-extracted metal is found in China . Mines in the country provide 97% of the world’s supply of rare earth elements, and that supply can be cut off if and when China sets export restrictions .(2) Restricting supply means prices for the metals climb .(3)
New mines in the United States and Australia, along with ones planned in Brazil, Canada and Vietnam, could stabilize the supply of rare earths . But new mines bring radioactive mining waste and potentially more fossil fuel energy needed to recover metal buried in poor ore .
So companies that make products using rare earth elements are looking for ways to recycle and reuse the metals . In 2010, Hitachi developed a method to recycle rare earth metals from hard drives and compressors . In March 2013, Honda announced a process to reuse the metals from batteries in hybrid cars .
University researchers are also creating new materials that can replace those in common products that rely on rare earth elements . An experimental electrode material for lithium ion batteries contains an organic molecule from plants called purpurin .(4) Quantum dots LEDs, made from silicon(5) or other metals, could replace LEDs colored using rare earth elements . Nanostructured films of manganese and gallium can exert magnetic fields of strength similar to rare-earth containing magnets .(6)
1 . Humphries, M . Rare Earth Elements: The Global Supply Chain . R41347, Congressional Research Service: 2012 .
2 . Cho, R . “Rare Earth Metals: Will We Have Enough?” Columbia University Earth Institute blog, Sept . 9, 2012 . http://blogs .ei .columbia .edu/2012/09/19/rare-earth-metals-will-we-have-enough/
3 . Trembley, J .-F . “Managing a Dearth of Rare Earths .” Chemical & Engineering News 2012, 90(14): 14-15 .
4 . Reddy, A . L . M ., Nagarajan, S ., Chumyim, P ., Gowda, S . R ., Pradhan, P . Jadhav, S . R ., Dubey, M ., John, G ., Ajayan, P . M . “Lithium storage mechanisms in purpurin based organic lithium ion battery electrodes .” Scientific Reports, 2012, 2, 960 .
5 . Patel, P . “LEDs Made From Silicon Quantum Dots Shine In New Colors .” Chemical & Engineering News, January 28, 2013 . http://cen .acs .org/articles/91/web/2013/01/LEDs-Made-Silicon-Quantum-Dots .html
6 . Nummy, T . J ., Bennett, S . P ., Cardinal, T ., Heiman, D . “Large Coercivity in Nanostructured Rare-earth free MnxGa films .” Applied Physics Letters, 2011, 99, 252506 .
Green Chemistry and Engineering: Towards a Sustainable Future 9Green Chemistry and Engineering: Towards a Sustainable Future
conditions most impacted the analysis .(24) Including bioprocesses in LCA would help the
pharmaceutical industry evaluate these catalysts .
Applications for enzymes can be found outside of the pharmaceutical industry, too . In 2012,
a chemical company, Buckman International, won an EPA Presidential Green Chemistry
Challenge Award for using enzymes to create stronger paper without added wood pulp or
chemical additives . The enzymes connect the fibers of cellulose within the paper, resulting in a
stronger end product . The enzymes also allow for increased production . Combined with energy
reductions, the new process saves the company an estimated $1 million per year .(25)
gReen solvenTsGreen solvent research in academic labs is targeted at finding new solvents . Scientists also
develop applications for interesting liquids like water, supercritical carbon dioxide (CO2), and
ionic liquids . Water is often not thought of as a potential solvent for organic reactions, because
many reagents are water-sensitive or insoluble in water . But some reactions, like an aqueous
Diels-Alder reaction between cyclopentadiene and butanone, run faster in water than in
organic solvents like methanol .(26, 27) Often the rate enhancement is due to hydrophobic
effects and hydrogen bonds that stabilize transition states . Running a reaction in water makes it
possible to use enzyme catalysts as well .
A 2007 analysis of green solvents that includes life cycle impacts ranks water and supercritical
CO2 as promising green alternatives to traditional organic solvents .(28) Many chemicals
do not dissolve in these solvents, but the researchers write that that fact is “more than
counterbalanced” by the ease of handling and separating these solvents, as well as their low
environmental impact .
Supercritical CO2 has properties between that of a gas and a liquid . It’s commonly used as
a dry cleaning solvent or to extract caffeine from coffee beans . Scientists can control what
compounds dissolve in the supercritical fluid by adjusting its density to tune its polarity . The
volatility of CO2 means that the supercritical fluid is easily removed after a reaction .
Ionic liquids are mentioned in almost half of the green solvent research published in Green
Chemistry in 2010 .(29) The structure of positive and negative ions in these liquid salts control
solubility and guide a reaction . Ionic liquids work as solvents for a variety of reactions (30), and
they can be designed to catalyze reactions too .(31) While ionic liquids might be interesting
substances from the perspective of basic research, their potential utility in industry is unclear
due to as-yet-to-be-determined disposal protocols on a large scale .(32)
The amount of research into various green solvents doesn’t match predicted needs for solvents
to reduce environmental damage, writes Philip Jessop of Queen’s University in Canada, in a
2011 perspective in Green Chemistry .(29) While Jessop supports basic research into solvents,
he asks his colleagues to consider their research topics carefully if they wish to reduce solvent-
caused environmental damage .
Green Chemistry and Engineering: Towards a Sustainable Future10 Green Chemistry and Engineering: Towards a Sustainable Future
Of course, the best way to reduce solvent use is to not use solvents in the first place .
It’s often thought that a solvent is needed to increase catalyst efficiency or improve the
enantioselectivity of a catalyzed reaction . Some asymmetric reactions, however, can be run just
by mixing the reagents together .(33)
alTeRnaTive eneRgy souRCes foR ReaCTionsRunning reactions can be energy intensive . When chemists boil a reaction, they simultaneously
cool the solvent vapors . The resulting droplets fall into the reaction so that the reaction never
runs dry . But this standard process requires energy to both heat and cool the reaction, in
addition to the water being constantly run through a condenser .
Therefore, some green chemists look to new energy sources to drive reactions . Microwave-
assisted reactions can be run in water at a small scale, often with accelerated rates due to
temperature and pressure effects . Reactions to build oxygen-, nitrogen- or sulfur-containing
rings common in medicinal chemistry can also be driven using microwaves, though these
reactions aren’t running on a process scale yet .(34) Alternatively, the energy from grinding
reagents together using a mortar and pestle or a ball grinder can be enough to trigger a
reaction .(35)
Ultrasound sonication is another energy source with useful applications such as deprotecting
an amine, protecting hydroxyls on sugars, or reducing an α,β-unsaturated ketone in a steroid .
The sound waves create areas of high and low pressure, much like ripples in a pond, as they
travel through liquid . Bubbles form in the low-pressure areas, collapse when they reach
high-pressure regions, and send shockwaves through the reaction . Surprisingly, ultrasound
sonication can influence the products of a reaction . When chemists stirred a suspension of
benzyl bromide and alumina-supported potassium cyanide, they retrieved diphenylmethane,
which contains two connected benzene rings, as the product of a Friedel-Crafts reaction . But
when they sonicated the reaction, the cyanide ion replaced the bromine atom, giving benzyl
cyanide as the product . The researchers suspect that the bubbles generated during sonication
masked the metallic catalytic sites on the solid support .(35)
ConTinuous pRoCessingTypical syntheses, whether in academic labs or batch processes, proceed through a series of
discrete steps and reactors . This creates large amounts of solvent and water waste . Continuous
processing, however, carries production in a steady flow by adding reagents to a stream of
liquid . Such reactions can address nine of the 12 principles of green chemistry .(36)
These experiments are often performed on the microscale by pumping reactants through
small channels . This scale has inherent safety benefits . Chemists can use smaller amounts of
potentially hazardous reagents, and the flow system gives them better control over conditions
that might otherwise lead to runaway reactions . Continuous processes can even be designed to
run short, multistep syntheses .(37)
Green Chemistry and Engineering: Towards a Sustainable Future 11Green Chemistry and Engineering: Towards a Sustainable Future
Microscale reactions can be scaled up by running one reactor for a long time, or by running
multiple reactors in parallel . It’s also possible to scale up flow reactions by increasing the width
of the tubes, and thus the volume of liquid traveling through them . A pilot-plant project made
more than 100 kilograms of 6-hydroxybuspirone over three runs of the flow process .(38)
Continuous production can be hampered by clogs in the lines or mechanical problems, like
leaking or valve failures . Thus, monitoring the reactions in the stream for blockages, as well as
product formation, helps to keep the flow processing moving . Chemists in Denmark built an
industrial-scale inline monitoring system for the production of allylcarbinol using a Grignard
reaction .(39) A Grignard reaction as the first step in a pharmaceutical synthesis, for example,
needs precise stoichiometric control of the Grignard reagent and ketone substrate to prevent
byproducts and yield loss . The monitoring system measures the amount of ketone left in the
product, and then controls the flow rate of the Grignard reagent into the reaction to maintain
the proper stoichiometry .
In a recent survey, eight of nine pharmaceutical companies reported using continuous
processing in pilot plants or on the production scale .(40) However, most companies in the
survey responded that they hesitate to build continuous-process plants when existing batch-
plant infrastructure meets demands .
IV . Reducing Toxicity By Design
Toxicologists track how chemicals harm the body, by studying their effects on biochemical
pathways, cells, and tissues . They also uncover relationships between the dose of a chemical
and its physical effect . These dose-response relationships are part of risk assessment and
hazard management plans . But one principle of green chemistry aims to do more than manage
risks; it challenges chemists to reduce a molecule’s toxicity during the design process, rather
than managing the effects after a molecule has been synthesized .
Currently, it’s not possible to fully predict the toxicity of any new molecule . But principles of
toxicology can help chemists identify characteristics of a molecule that might impart toxicity .
(41) Certain molecular structures bind to metabolic enzymes . Other electron-poor molecules
are carcinogenic because they bind to DNA . And fat-soluble molecules can accumulate in fat
cells and not be cleared from the body .
Medicinal chemists can exploit some of these structures to help develop killer drugs specific
for diseased cells . Green molecular designers, however, want to avoid those structures, as they
want to prevent a molecule from causing biological harm .
Green Chemistry and Engineering: Towards a Sustainable Future12 Green Chemistry and Engineering: Towards a Sustainable Future
ReduCing endoCRine disRupTionEndocrine disruptors are harmful molecules that behave like hormones in humans and alter
the body’s natural signaling system . Endocrine disruptors are thought to be linked to health
conditions such as obesity, cancer, diabetes, and infertility . Now a new protocol helps chemists
design molecules to reduce their endocrine-disrupting effects .
Bisphenol-A (BPA), a phthalate used as a plasticizer in polycarbonate plastics, is an example
of a potentially endocrine-disrupting chemical . It’s also found in the linings of canned food
and cash register receipts . Many products advertise that they are BPA-free, due to consumer
concerns about ingesting BPA . Chemical companies are searching for molecules to replace BPA
for food and beverage applications, but they’re struggling to find something that’s an equally
effective replacement .(42)
A new tiered system of tests, developed by a team of 23 scientists, might help chemical
companies determine if a new molecule is a potential endocrine disruptor .(43) The first tier
involves computer modeling based on physical properties, chemical reactivity, and estimates of
biological reactivity using structural similarities . The second tier involves biochemical pathway
screening . Then a molecule is tested in tissues of increasing complexity — from cells to whole
amphibians to mammals .
The study of endocrine disruption is still a growing field, so protocols will evolve to include
assays that incorporate knowledge as it is discovered .(44) For example, a growing body of
evidence suggests that chronic, low doses of endocrine disruptors like BPA may cause physical
harm .(45) That means a typical interpretation of toxicology — reducing risk by preventing
exposure to harmful doses — may not apply to this class of chemicals .
Green Chemistry and Engineering: Towards a Sustainable Future 13Green Chemistry and Engineering: Towards a Sustainable Future
V . Renewable Feedstocks
The ingredients for many chemicals and materials come from petroleum and natural gas
processing . One principle of green chemistry calls for using renewable feedstocks when
technically and economically possible, instead of drawing on materials that deplete
natural resources .
Plants are seen as a source of sugars for biofuel production . Starch from corn is an easily
accessible sugar source, but it’s impractical to scale up biofuel production using corn .
Every acre of corn destined for biofuel production is one less acre that’s not in agricultural
production . However, there are other fast-growing plants like switchgrass and a species of
poplar tree that could make attractive sugar sources, while avoiding a “food versus fuel” debate .
However, it’s difficult to break apart these woody plants into sugars needed for fuel production .
Tough fibrils of lignocellulose reinforce plant cell walls .(46) Releasing the sugars in that
lignocellulose is key to getting the maximum amount of fuel from a plant .
Chemical catalysts can convert plant matter to oxygenated fuels like ethanol, furfural, and
levulinic acid .(47) Virent, a biofuel company in Wisconsin, converts sugars to hydrocarbons
— essentially the same blend as gasoline — using an aqueous process and chemical catalyst .
Alternatively, engineered microbes can consume sugars and produce a fatty acid methyl ester
or farnesane for biodiesel .
Multiple Highways
Many starting points lead to many end points for biofuels .
STARCHES/SUGARS Corn grainSugarcane
Aqueous sugarsFermentation
Aqueous-phase processing
Ethanol or butanolDiesel fuel or jet fuel
GasolineDiesel fuelJet fuel
LIPIDSSoybeansOther oilseedsAnimal fatAlgae
Vegetable oil/animal fat EsterificationHydrotreating
Diesel fuelJet fuel
LIGNOCELLULOSECrop residuesForest wasteMunicipal wasteEnergy crops
Hydrolysis/enzymes
Gasification
Pyrolysis
Aqueous sugars
Synthesis gas
Biocrude oil
Aqueous-phase processing
Fischer-Tropsch chemistry Fermentation
Catalytic cracking Hydrotreating
GasolineDiesel fuelJet fuelEthanol
Green Chemistry and Engineering: Towards a Sustainable Future14 Green Chemistry and Engineering: Towards a Sustainable Future
Currently the economics of biofuel production still lie in favor of petroleum-based fuel . But
a biofuel plant can offset its production of low-value fuel by also producing high-value bulk
chemicals .(48) In 2004, the U .S . Department of Energy listed 15 chemicals as top targets to
make in a biorefinery . Included on the list were glycerol, succinic acid, aspartic acid, and
furandicarboxylic acid . An experimental small scale biorefinery from researchers at the
City University of Hong Kong transforms wasted pastries from Starbucks into succinic acid .
Companies like BioAmber, an industrial biotechnology firm in Minneapolis, are looking to use
more traditional sugar sources, and won a 2011 EPA Presidential Green Chemistry Challenge
Award for its microbial production of succinic acid from glucose, corn sugar, and corn stover .
(49) BioAmber operates a plant in France that produces 3,000 metric tons of succinic acid a year .
It plans to open a larger factory in 2013, capable of producing 11,000 additional metric tons
at full capacity . A wave of upcoming factory openings for other biobased chemicals, including
isobutyl alcohol, glucaric acid, acetic acid, and farnesene, carves out a place for biobased
chemical production in the industry, although the bottom-line profitability of these companies
is still unknown .(50) What is known is that the chemicals being produced are destined for
solvents, detergents, and coatings .
Companies large and small are working on developing ingredients for rubber(51),
fragrances(52), and plastics(53) as well . Polylactic acid (PLA) made from corn sugar is a
common biobased plastic used in compostable cups, plates, and utensils . A material that
mimics the structure and properties of polyethylene terephthalate (PET) can be made from
lignin-derived vanillin and methanol-derived acetic acid .(54)
It’s also possible to make traditional plastics, like polystyrene and PET, at least partially from
renewable feedstocks . Again, these traditional plastics from renewable feedstocks cannot yet
compete economically with their petroleum-derived relatives . However, interest from large
companies like Coca-Cola and Heinz might increase demand for these biobased plastics and
might help give the market some momentum .(53)
But a recent LCA of plastics shows that switching to a biobased feedstock doesn’t improve the
“greenness” of the process overall .(55) PLA and polyhydroxyalkanoate plastic from corn grain
or stover get high marks compared to the petroleum-derived plastics when analyzing their
adherence to green design principles . But production of 10 different traditional plastics, like
polystyrene, propylene, and polycarbonate, has less environmental impact in terms of nutrient
overloading, ecotoxicity, ozone depletion, and carcinogenicity than bioplastic production .
That’s because the biobased plastics the researchers analyzed come from corn that requires
fertilizer, pesticides, and farmland . Microbial fermentation and other chemical processing
steps also contribute to the negative environmental impact from biobased plastic feedstocks .
This bioplastics LCA did not include recycling or biodegradation in the analysis; negative
environmental impacts might be found to be reduced if recycling and biodegradation were
considered in the analysis .
Green Chemistry and Engineering: Towards a Sustainable Future 15Green Chemistry and Engineering: Towards a Sustainable Future
VI . Green Chemistry in Industry
Three roundtables, convened by the ACS Green
Chemistry Institute, unite companies in various
chemical industries to spread green chemistry
principles through their industries .(56) There’s
a roundtable for manufacturers and one for
formulators, companies that mix chemicals to
make shampoos, cleaners, and/or cosmetics . The
third, and oldest, is the Pharmaceutical Roundtable,
started in 2005 as a partnership between Eli Lilly
& Co ., Merck & Co ., and Pfizer . Today the group has
grown to 16 members, including enzyme company
Codexis and supplier DSM .
Of the different kinds of chemical industries,
pharmaceutical companies produce the smallest
amount of product and the largest amount of
waste . Refining petroleum produces 106 to 108
tons of chemicals each year, compared to tens
to thousands of tons of pharmaceuticals . But
pharmaceutical production generates up to 1,000
times more waste, as measured by E-factor, than
petrochemical production .(57)
Due in part to the efforts of the ACS
Pharmaceutical Roundtable, a group of
process chemists in the pharmaceutical and
fine chemical industry that was convened by
ACS Green Chemistry Institute, the principles
of green chemistry are spreading through the
industry . The roundtable produces biannual
reviews of green chemistry literature of interest
to the pharmaceutical industry .(58–62) The
group also develops tools like solvent selection
guides to help chemists make greener choices
during product design . It also funds academic
green chemistry research applicable to industry
and brainstorms new directions for that
research .(24, 63)
biogas and beeR WasTe poWeR food faCToRies
Companies in the food industry, large and small, turn waste into energy for their factories . Straus Family Creamery, a family-owned dairy just north of San Francisco, converts manure to energy that powers the dairy . (1) Workers flush manure and wastewater from rinsing the barns into a holding pond that separates the solids from the liquids . The liquid manure runs into a second pond covered with a tarp, called an anaerobic digester . Bacteria in the pond convert the manure to biogas, which is mostly methane . They collect that methane and use it to run a generator that powers the dairy . Heat from the generator warms water used to clean barns and excess energy is returned to the area’s electrical grid .
Anaerobic digesters can also be used on a larger scale . This summer, one will open in Wisconsin to process liquid waste from cheesemaking, called whey, from five cheese factories and a soy food ingredient factory .(2) Thick Greek yogurt gets its consistency due to extra straining, so these yogurt factories also have to dispose of whey . The Fage factory in New York funnels some of its whey waste to an anaerobic digester, which was able to completely power the factory when Hurricane Sandy hit the area last October .(3) The Chobani factory, about 50 miles east of the Fage factory, trucks its sugar-filled liquid waste to farmers who use it as fertilizer .
Dairy waste isn’t the only thing that can be fed to microbes for biogas . The Campbell Soup Company is building an anaerobic digester in Ohio to process waste from soup, sauce and drink production .(4) Switching to this source of renewable energy, the company expects to cut its greenhouse gas emissions due to electricity by the equivalent of 3,000 cars .
Sometimes waste from the food industry can be burned to create power for a plant . The Alaskan Beer company in Juneau is the first craft brewery to use spent grain as the sole fuel source for their steam boiler .(5) Spent grain must first be dried before it can be burned as fuel . But spent grain is not an efficient fuel source if it takes more energy to dry the grain than comes from burning it . The brewery found a way to create drier grain by improving the efficiency of how they remove the mash from the liquid beer . Then they combined their 20-year experience running a grain dryer to help design an efficient grain-powered steam boiler . The company estimates this new process will cut their fuel consumption in half .
1 . Straus Family Creamery . Methane Digester . http://strausfamilycreamery .com/values-in-action/methane-digester
2 . Content, W . “GreenWhey to open $28 million food waste-to-energy project .” Milwaukee-Wisconsin Journal Sentinel, Feb . 19, 2013 . Available at: http://www .jsonline .com/business/greenwhey-to-open-28-million-food-wastetoenergy-project-gi8qo71-191938931 .html
3 . Charles, D . “Why Greek Yogurt Makers Want Whey To Go Away .” National Public Radio, November 21, 2012 . Available at: http://www .npr .org/blogs/thesalt/2012/11/21/165478127/why-greek-yogurt-makers-want-whey-to-go-away
4 . Campbell Soup Company . “Campbell Soup Company and CH4 Biogas, L .L .C . Create Ohio’s First Commercial Biogas Power Plant .” November 5, 2012 . Available at: http://investor .campbellsoupcompany .com/phoenix .zhtml?c=88650&p=irol-newsArticle&ID=1754130&highlight=
5 . Alaskan Beer Company . “Alaskan now serving beer-powered beer .” January 15, 2013 . Available at: www .alaskanbeer .com/press-room-2/312-alaskan-now-serving-beer-powered-beer-press-release .html
Green Chemistry and Engineering: Towards a Sustainable Future16 Green Chemistry and Engineering: Towards a Sustainable Future
A recent survey of
21 pharmaceutical
and fine chemical
companies showed
that about 88% of them
had policies regarding
green chemistry .
(4) Green solvents
are a priority for all
companies surveyed . Process design, energy use, green metrics, and sustainable raw materials
were also issues of high importance to the companies . Some of the basic principles of process
design — waste minimization, reducing energy use, increasing safety — dovetail with the 12
principles of green engineering . But other green chemistry technologies and approaches need
more research to be used in industry . Continuous processing and LCA of bioprocesses are two
important green engineering research areas important to the pharmaceutical industry .(24)
solvenT useAt GlaxoSmithKline (GSK), solvents contributed 85-90% of the total mass of non-aqueous
materials used to make a drug in 2005 .(32) A growing awareness in green chemistry has
influenced solvent use among companies in the Pharmaceutical Roundtable . In 2012, about
54% of the mass of a product came from solvents .(4) Many common organic solvents carry
inherent environmental, health, and safety risks . Emissions from volatile solvents can destroy
the atmospheric ozone layer . Other solvents, like benzene, are classified as carcinogens .
Flammable solvents also pose storage risks . In 1998, chemists at GSK developed a solvent
selection guide to help their chemists pick solvents to maximize yield and minimize risk . The
first version of the chart ranked solvents in terms of their risks to the environment, health,
and safety . Now the amount of information involved in the rankings has expanded, while
the presentation is still simple and easy to read . The latest edition of the guide ranks 110
solvents by preferred use based on their physical properties, flammability, and waste handling .
(65) A quick reference guide explains the rankings . Solvents with a high boiling point are
disfavored because they require energy to remove them by distillation . For other solvents,
the environmental damage caused during production and transport is greater than that from
their emissions alone . The chart also includes an LCA ranking for each solvent to help chemists
consider solvent production in their selection . A more detailed version of these rankings is
available for process chemists who need more information when choosing solvents compared
to medicinal chemists running smaller-scale experiments . Other companies have their own
solvent selection guides, too . However, any chemist can access the solvent selection guide
created by the ACS GCI Pharmaceutical Roundtable .
Solvent use is declining in industry, particularly for the most harmful chlorinated solvents .
Of 21 pharmaceutical and fine chemical companies surveyed in 2011, none use chloroform
or carbon tetrachloride .(4) Dichloromethane is used only when necessary as well . Academic
Green Chemistry and Engineering: Towards a Sustainable Future 17Green Chemistry and Engineering: Towards a Sustainable Future
journals are encouraging the use of “greener” solvents too . Editors at Organic Process Research
and Development will not publish papers using solvents like benzene, carbon disulfide, or
chloroform unless the authors have analyzed alternative solvents or justified the use of those
solvents .(66)
Quantitative metrics of solvent selection charts can help chemists improve the “greenness”
of processes . But sometimes qualitative determinations of sustainability are a matter
of perspective . In the ibuprofen synthesis mentioned at the beginning of this chapter,
hydrofluoric acid used in the first step usually would not be considered a low-risk solvent . Its
fumes are irritants, and liquid HF can seep through skin and pull calcium out of bones . But in
this synthesis, anhydrous HF serves both as reagent and solvent, reducing waste . The liquid is
also recycled, thus reducing solvent consumption .(67)
VII . Education
Chemical accidents, like the release of methyl isocyanate in 1984 at a factory in Bhopal, India
that killed more than 3,800 people, help foster a negative public perception of chemistry . Green
chemistry seeks to prevent such tragedies by reducing hazards and toxicity . Environmentally
aware students who may be wary of chemicals can connect to chemistry through the
sustainable values of green chemistry .
Beyond Benign, a foundation based in Massachusetts, brings green chemistry concepts to
kindergarten through high school students .(68) The foundation also sponsors a fellowship
program for undergraduate and graduate students to be green chemistry ambassadors around
Boston . The fellows do outreach with local groups and schools and develop their own green
chemistry experiment .
The ACS Summer School on Green Chemistry and Sustainable Energy is a week-long program
aimed at educating graduate students and postdoctoral scholars from the U .S ., Canada, and
Latin America on the basic concepts of sustainability, green chemistry and engineering, and
sustainable energy technologies . Many students who have participated in the program return
to their labs eager to apply the knowledge they’ve gained about green chemistry to their
research .
lab expeRiMenTsIntegrating green chemistry into an already packed undergraduate curriculum is possible,
but it can be challenging . The University of Oregon, for example, has had green chemistry
laboratory courses for more than a decade .(69) To further this integration more broadly, Beyond
Benign proposed last year that colleges and universities sign a Green Chemistry Commitment,
pledging to absorb green chemistry into their curricula .(70)
Green Chemistry and Engineering: Towards a Sustainable Future18 Green Chemistry and Engineering: Towards a Sustainable Future
For introductory general laboratory courses,
at least, there are advantages to incorporating
experiments from green chemistry . These
experiments have less waste, lower liability, and
lower energy costs, with the added benefit of
increased safety . Green chemistry is especially
advantageous for old labs that do not have proper
ventilation because the experiments can be
performed on bench tops .(71)
There are several resources for people interested in
learning more about green chemistry experiments .
The Greener Educational Materials (GEMs) database,
run by the University of Oregon, is an interactive,
online collection of chemistry education materials
and experiments focused on green chemistry .(69)
Users can search the database by a specific chemical
concept they want to teach, like enzymes, boiling
point, or molecular reactivity . They can also search
by lab technique, or identify experiments that
demonstrate particular principles of green chemistry .
Some experiments teach “greener” lab techniques, like performing a multi-step, small-scale
synthesis without metal catalysts . Undergraduates at Harvey Mudd College in California
developed a green synthesis of warfarin, a drug that reduces blood’s ability to form clots .
(72) The students used an organocatalyst, rather than transition metals, to introduce the
stereochemistry needed in the product .
There’s even an
opportunity to
learn about green
chemistry beyond
the 15 college
programs currently
offered in the United
States . The University
of California, Berkeley
Extension offers
continuing education
for professionals from
materials science
to environmental
Green Chemistry and Engineering: Towards a Sustainable Future 19Green Chemistry and Engineering: Towards a Sustainable Future
management to sharpen their knowledge of green
chemistry .(73) Eventually all of the courses for the
certificate will be available online .
VIII . Conclusions
Green chemistry is spreading from academic labs
into industry as a way to reduce costs, as well as
environmental, health and safety risks . Applications of the
12 guiding principles are found on scales small and large,
from choosing ingredients for reactions that minimize
waste and risk to metrics that quantify waste and process
efficiency . And principles of engineering and process
design lead green chemists to track energy use during
production, search for sustainable raw materials, and build
biodegradable or recyclable products to prevent waste .
But green chemistry is still not widely implemented .
Current estimates put green chemistry products at only
1% of the products from the chemical sector . Several
barriers hinder implementation of green chemistry
in the United States .(74) The challenge of developing
sustainability metrics keeps companies from evaluating
their processes and incorporating green chemistry into
business decisions . Regulations around drug production
and the investment tied up in existing chemical plants
hinder the development and implementation of new
technologies . The interdisciplinary nature of green
chemistry also challenges the specialized knowledge
gained in current training and industrial work experience .
In the U .S ., government policies that forward knowledge
sharing or provide economic incentives can help spur
green chemistry innovation .
The prospects and barriers for green chemistry are
different in a developing country like China . The current
growth of the Chinese chemical industry offers great
potential for incorporating green chemistry practices as
a way to combine the goals of environmental protection
and economic growth .(75) Some of the barriers to
suMMeR sChool on gReen CheMisTRy and susTainable eneRgy
The ACS Summer School on Green Chemistry and Sustainable Energy has educated almost 600 graduate students and postdoctoral scholars since it launched in 2003 . Participants engage in lectures, case studies, discussions, and poster sessions as they assess the greenness and sustainability of specific technologies . World-class researchers—including Joan Brennecke of the University of Notre Dame, Philip Jessop of Queen’s University, and Eric Beckman of the University of Pittsburgh—share their expertise in green chemistry and sustainable energy throughout the week-long program .
The Summer School has a significant impact on the participants, and a number of former students who are now faculty members have sent their own students to the program . A survey of 274 students who participated in the Summer School from 2003-2007 garnered a 64 percent response rate . Eighty-six percent of the respondents indicated they have used green chemistry in their careers since participating in the Summer School, and 90 percent reported that the Summer School had a positive influence on their career paths . Connections made during the Summer School are remarkably strong, with 80 percent of the survey respondents still in contact with at least one other participant .
Feedback from participants is uniformly positive on post-Summer School surveys . One student who attended the 2010 Summer School commented, “I got more great ideas for my research at this course than I ever have before at any other class or conference . The social aspect was also extremely awesome and I made tons of friends and contacts .” A 2012 Summer School participant observed that the best thing about the course was the “diversity of backgrounds of participants and speakers! I had no idea that students from so many areas of chemistry could all be green chemists!” The 2013 Summer School will once again be held at the Colorado School of Mines with support from the ACS Petroleum Research Fund .
Green Chemistry and Engineering: Towards a Sustainable Future20 Green Chemistry and Engineering: Towards a Sustainable Future
adopting green chemistry widely in the country overlap
with general barriers to innovation, like markets,
economics, regulations, and culture . Nevertheless,
implementing green chemistry in new factories as the
chemical industry grows in China could impact the
trajectory of the industry for decades .
Further adoption of green chemistry could improve the
public’s perception of the field of chemistry as a whole .
(76) Proponents of green chemistry say the field combines
environmental, health, and safety benefits with the
traditional goals of economic gains in industrial chemistry
and knowledge gains through academic research .
Economics and knowledge, while important reasons to
pursue chemistry, can conflict with the public’s perception
of chemistry as a toxic undertaking, particularly when
safety, sustainability, and protection of the environment
are on their minds . Promoting green chemistry research,
and its adoption into industry, through federal policies
and education might help the field of chemistry bridge the
divide between its values and those of the public . Thus, the
growth of green chemistry can lead to gains in other areas:
profits, public perceptions, and protecting our planet .
inspiRing fuTuRe CheMisTs ThRough gReen CheMisTRy k-12 ouTReaCh
A common perception of a chemist is a wild-haired person dressed in a lab coat who sets things on fire . Amy Cannon and John Warner, co-founders of the green chemistry education non-profit Beyond Benign, argue that chemists themselves help create this misperception . “When we perform demonstrations to a group of school children to get them excited about science we do exactly what we would hope never happens in the “real world”: explode things and set them on fire,” they write .(1) Green chemistry experiments offer a way to perform demonstrations showing that chemistry does not have to be hazardous or environmentally damaging . Beyond Benign works to bring green chemistry to K-12 classrooms, through demonstrations, teacher training and curriculum development . Another project brings green chemistry to the broader public by connecting artists and scientists to develop community exhibits . One classroom project has students build dye-sensitized solar cells using a titanium dioxide semiconductor, blackberries as the dye, and pencil lead as the counter electrode . The experiment is an opportunity to talk about alternative energy and chemical concepts like oxidation and reduction of the electrolyte . Students test their solar cells to see how much energy they can harvest from the sun . Another program aims to specifically help school-age girls get excited about chemistry . In 2011, Aisling M . O’Connor, at Fitchburg State University in Massachusetts, worked to expand the chemistry activities performed by the nonprofit Science Club for Girls . The students meet for four days during vacation to do experiments related to personal care products . The girls learn about acids, bases and chemical bonding as they make fizzy bath balls from baking soda and citric acid . The final project is to make soap using lye, vegetable oil and lavender oil . Then the girls compare the safety of their ingredients to those used in a few commercially available soaps . By exposing school-age children to chemistry early in their education, these outreach efforts hope to increase students’ understanding of science by engaging them in activities that connect science to their daily lives . 1 . Cannon, A . S . and Warner, J . C . “K-12 Outreach and Science Literacy Through Green Chemistry .” In Green Chemistry Education: Changing the Course of Chemistry; Anastas, P .T ., Levy, I . J ., Parent, K . E ., Eds .; ACS Symposium Series 1011; American Chemical Society: Washington, DC, 2009 .
2 . Ritter, S . K . “After-School Sustainability .” Chemical & Engineering News 2011, 89(41): 46-47 .
Green Chemistry and Engineering: Towards a Sustainable Future 21Green Chemistry and Engineering: Towards a Sustainable Future
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Green Chemistry and Engineering: Towards a Sustainable Future 23Green Chemistry and Engineering: Towards a Sustainable Future
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Appendix A: 12 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, P . T .; Warner, J . C . Green Chemistry: Theory and Practice, Oxford University Press: New York, 1998, p . 30 .
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Appendix B: 12 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, process 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 material 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”,
Environmental Science & Technology 2003, 37, 94A-101A .