1 of Green Chemistry The idea of green

1 Introduction

Green chemistry is a tool which can help
industries achieve their environmental goals. It is an approach that strives to
minimise waste production, (to??)
promote the use of renewable and recycled resources, and to achieve highest
possible energy efficiency1. It can be used by any processing
industry, but has been of particular importance for the pharmaceutical industry
in recent years, as it strives
to improve its environmental performance.

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1.1 Definition of Green Chemistry

The idea of green chemistry was introduced
by the United States of America Environmental Protection Agency (EPA) in the
early 1990s, which encouraged manufacturers to seek new technologies or
materials that would be inherently benign, in order to avoid penalties for
exceeding new emission limits1. It provided an
alternative for companies; instead of installing treatment technologies they
could innovate their processes.

Green chemistry was first defined in 1998,
as “the utilization of a set of principles that reduces or eliminates the use
or generation of hazardous substances in the design, manufacture and
application of chemical products”2. This chemical philosophy
involves the redesign of chemicals and processes at the molecular level, using
an inherently safer approach to deliver more environmentally benign products
and processes. The guiding principle is benign by design.

Although green chemistry principles have
been established for over 20 years, companies have only recently begun
large-scale implementations of these concepts. This is because green chemistry
has most often been associated with the production of environmentally friendly
products, and thus perceived as only providing environmental benefits.
Companies are now coming to understand however, that green chemistry also
provides significant economic benefits. This is achieved by reducing costs of
safety and insurance, waste disposal, materials, utilities, land use and more1.

 

 

 

1.2 Principles of Green Chemistry

The 12 principles of green chemistry1
are listed below:

1.     
Prevention:
It is better to prevent waste that to treat or clean up waste after it has been
created.

2.     
Atom
economy: Synthetic methods should be designed to maximise 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 achieve their desired
function while minimising their toxicity.

5.     
Safer
solvent and auxiliaries: The use of auxiliary substances (eg. solvents) should
be made unnecessary wherever possible and innocuous when used.

6.     
Design for
energy efficiency: Energy requirements of chemical processes should be
recognised for their environmental and economic impacts and should be
minimised.

7.     
Use of
renewable feedstocks: A raw material should be renewable rather than depleting
whenever technically and economically practicable.

8.     
Reduce
derivatives: Unnecessary derivatization (eg. use of blocking groups,
protection/deprotection) should be minimised or avoided if possible, because
such steps require additional reagents and can generate waste.

9.     
Catalysis:
Catalytic reagents 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 minimise the potential for chemical accidents (eg.
releases, explosions).

 

1.3 The Presidential Green
Chemistry Challenge Awards

The Presidential Green Chemistry Challenge
Awards is a program created by the EPA in 1996 to promote innovation and
research of green chemistry for environmental protection3. Each year nominations are
accepted from government, industrial or academic groups or individuals, to
compete for recognition of their innovative technologies that incorporate the
green chemistry principles. The awards are divided into three areas: use of
greener synthetic pathways, use of greener reaction conditions and design of
greener chemicals. By recognising innovative scientific solutions to real-world
environmental problems, this awards program has significantly reduced the
hazards associated with designing, manufacturing, and using chemicals.

From its commencement
through to 2017, the award-winning technologies have jointly eliminated the
annual use of 826 million pounds of hazardous chemicals, 21 billion gallons of
water and the release of 7.8 billion pounds of carbon dioxide to the atmosphere3.

 

1.4 Green Chemistry in the
Pharmaceutical Industry

While the pharmaceutical industry focuses
on reducing disease and improving the standard of living for people all over
the world, its performance has historically been lacking in the environmental
arena. For example, the pharmaceutical industry uses large amounts of energy
and produces more waste than other big industries such as petrochemical, bulk
and fine chemicals4.

Green chemistry has since provided a means
for this industry to make substantial progress in its environmental targets,
while also delivering economic benefits. There are two measures used to
quantify waste generated by chemical processes5:

1.     
E factor:
This is the mass of waste generated per mass of product (API) made.

2.     
Process
mass intensity (PMI): The unit of raw material used per unit of product made.

Both measures take into account the amount
of non-reusable reactants, auxiliaries and solvents used in the process.
Therefore, a lower value for both E factor and PMI is desirable, and is the
goal that the pharmaceutical industry is striving towards. It is important to
note that, in the pharmaceutical industry, water is usually taken into account when
performing E factor calculations.
Originally water was excluded from E factor
calculations, as it was thought including it would lead to high E factors, that
in many cases would make meaningful comparisons of processes difficult6.

Manufacturing costs are estimated to be as
high as 38% of overall pharmaceutical expenses7. Therefore, another key
factor driving the adoption of green chemistry into pharmaceutical processes is
the potential cost savings due to reduced solvent use, enhanced yield and
continuous processing, achieved by green chemistry approaches. When implemented
correctly however, green processes also result in reduced regulatory and social
risks; ultimately improving a company’s triple bottom line.

 

 

2 Green Chemistry Techniqu

1
Marteel-Parrish, A. Green Chemistry and Engineering: A Pathway to
Sustainability, 2014.

 

2
Anastas, P. T. Green chemistry: Theory and practice, 1998.

3 Information about the Presidential Green
Chemistry Challenge, 2017.

4 Sharma,
V., Pharma Bio World, 2015.

5 Albini
A. Paradigms in Green Chemistry and
Technology, 2016.

6 Sheldon,
R. A. Journal of Chemical Technology and
Biotechnology, 1997.

7 Fortunak, J.M. Future Medicinal Chemistry, 2009.