1587884932985_final book 26-04-20

5. GREEN CHEMISTRY

5.1. INTRODUCTION :-

Green Chemistry is the design of chemical products and processes that reduce or eliminate
the use and generation of hazardous substances.
The green chemistry approach seeks to redesign the materials that make up the basis of our
society and our economy—including the materials that generate, store, and transport our
energy—in ways that are benign for humans and the environment and possess intrinsic
sustainability.
The concepts and practice of Green Chemistry have developed over nearly 20 years into a
globe-spanning endeavour aimed at meeting the ‘‘triple bottom line’’—sustainability in
economic, social, and environmental performance.

5.1.1. HISTORY:-

The idea of green chemistry was initially developed as a response to the Pollution
Prevention Act of 1990, which declared that U.S. national policy should eliminate pollution
by improved design (including cost-effective changes in products, processes, use of raw
materials, and recycling) instead of treatment and disposal. Although the U.S.
Environmental Protection Agency (EPA) is known as a regulatory agency, it moved away
from the “command and control” or “end of pipe” approach in implementing what would
eventually be called its “green chemistry” program.
By 1991, the EPA Office of Pollution Prevention and Toxics had launched a research grant
program encouraging redesign of existing chemical products and processes to reduce
impacts on human health and the environment. The EPA, in partnership with the U.S.
National Science Foundation (NSF), then proceeded to fund basic research in green
chemistry in the early 1990s.

The introduction of the annual Presidential Green Chemistry Challenge Awards in 1996 drew
attention to both academic and industrial green chemistry success stories. The Awards
program and the technologies it highlights are now a cornerstone of the green chemistry
educational curriculum.

The mid-to-late 1990s saw an increase in the number of international meetings devoted to
green chemistry, such as the Gordon Research Conferences on Green Chemistry, and green
chemistry networks developed in the United States, the United Kingdom, Spain, and Italy.
The 12 Principles of Green Chemistry were published in 1998, providing the new field with a
clear set of guidelines for further development (1). In 1999, the Royal Society of Chemistry
launched its journal Green Chemistry.
In the last 10 years, national networks have proliferated, special issues devoted to green
chemistry have appeared in major journals, and green chemistry concepts have continued
to gain traction. A clear sign of this was provided by the citation for the 2005 Nobel Prize for
Chemistry awarded to Chauvin, Grubbs, and Schrock, which commended their work as “a
great step forward for green chemistry”

5.1.2. FATHER OF GREEN CHEMISTRY :-

Paul T. Anastas (born May 16, 1962 in Quincy, Massachusetts) is an American scientist,
inventor, author, entrepreneur, professor, and public servant. He is the Director of Yale
University’s Center for Green Chemistry and Green Engineering, previously he served as the
Science Advisor to the United States Environmental Protection Agency as well as the
Agency's Assistant Administrator for Research and Development, appointed by President
Barack Obama. Anastas is known widely as the "Father of Green Chemistry" for his work on
the design and manufacture of chemicals that are non-hazardous and environmentally
benign. He is also a champion of sustainability science and innovation for environmental
protection. Anastas has brought worldwide attention to the power of molecular design to
help the environment. He has published scores of articles as well as ten books, including his
seminal work with co-author John Warner, Green Chemistry: Theory and Practice.

Their 12 Principles of Green Chemistry are the basis for high school, college and graduate
programs around the world and have significantly altered the landscape of the chemicals
industry in the United States and other countries.

5.1.3. DEFINITION:

Green Chemistry is 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.

There is increasing pressure from both society and governments for chemistry-based
industries to become more sustainable through development of eco-friendly products and
processes that both reduce waste and prevent toxic substances from entering the
environment.

5.1.4. WHAT IS GREEN CHEMISTRY?

The chemical industry is vitally important to the world economy; however the success of the
industry has led to some environmental damage and a low public perception of the
industry.
In order to prevent further environmental damage and to encourage more young people
into the industry, the public acceptability needs to be raised by adoption of greener and
cleaner processes and green product design.Green chemistry is an approach to the design,
manufacture and use of chemical products to intentionally reduce or eliminate chemical
hazards.2 The goal of green chemistry is to create better, safer chemicals while choosing the
safest, most efficient ways to synthesize them and to reduce wastes.

5.1.5. GOALS OF GREEN CHEMISTRY?

1. To reduce adverse environmental impact, try appropriate and innovative choice of
material and the chemical transformation.
2. To develop processes based on renewable rather than non-renewable raw materials.
3. To develop processes that are less prone to obnoxious chemical release, fires and
explosions.
4. To minimise biproducts in chemical transformation by redesigning of reactions and
reaction sequences.
5. To develop products that are less toxic.
6. Design synthetic methodologies that reduce or eliminate the use and or generation of
toxic products.
7. All possibly roots may be examined.
8. Most appropriate root (without hazardous starting materials and or products) should be
used.
9. No chemical accident

E.g. Synthesis of Adipic Acid - used for making nylon, PU, lubricants, plasticizers.

HERE IS A SMALL QUIZ:

1. Green chemistry aims to?
a) Design chemical products and process that maximize profits
b) Design safer chemical products and processes that reduce or eliminate the use and
generation of hazardous substances
c) Design chemical products and processes that work most efficiently
d) Utilize non-renewable energy

2. Dr. Paul Anastas & Dr. John Warner created 10 Principles of Green Chemistry to
reduce or eliminate the use and generation of hazardous substances?
a) True
b) False

3. Which of the following are among the 12 Principles of Green Chemistry?
a) Design commercially viable products
b) Use only new solvents
c) Use catalysts, not stoichiometric reagents

d) Re-use waste

4. Green chemists reduce risk by?
a) Reducing the hazard inherent in a chemical product or process
b) Minimizing the use of all chemicals
c) Inventing technologies that will clean up toxic sites
d) Developing recycled products

5. Which of the following is a challenge for green chemists?
a) Awareness of the benefits of green chemistry
b) Developing chemicals that are recyclable
c) Training for cleaning up chemical spills
d) Knowing when to reduce and eliminate hazardous waste

Q.NO: 1 2 3 4 5

ANS: b b c a d

5.2. THE TWELVE PRINCIPLES OF GREEN CHEMISTRY:

Green chemistry, then, is an ongoing attempt to address the problems that chemicals and
chemical processes can sometimes cause. As a concept, it emerged in the 1990s, and in
order to further focus the efforts of chemists towards it, the 12 principles detailed here
were published. They were created by Paul Anastas and John Warner, and are essentially a
checklist of ways to reduce both the environmental impact and the potential negative
health effects of chemicals and chemical synthesis.



5.2.1. Waste Prevention:

The saying “prevention is better than cure” is true not only in the healthcare
industry but also the chemical industry. It is essential in green chemistry to
design processes that reduce wastages as it is better to prevent it in the first
place than to treat or clean up the waste after its creation. This tenet simply states
that chemical processes should be optimized to produce the minimum amount of waste
possible.

5.2.2. Atom Economy:

All chemicals in green chemistry are a result of reactions at an atomic level. So
by figuring out the atoms that are incorporated into the final product and the
atoms that are wasted, the efficiency of the reaction can be increased.
Manufacturers need to measure the atom economy percentage
Atom economy is a measure of the amount of atoms from the starting material that are
present in the useful products at the end of a chemical process. Side products from
reactions that aren’t useful can lead to a lower atom economy, and more waste. In many
ways, atom economy is a better measure of reaction efficiency than the yield of the
reaction; the yield compares the amount of useful product obtained compared to the
amount you’d theoretically expect from calculations. Therefore, processes that maximize
atom economy are preferred.

Atom = Molecular Weight of desired product X 100%
Economy Molecular Weight of all reactants

5.2.3. Less Hazardous Chemical Synthesis:

Ideally, we want chemicals we create for whatever purpose to not pose a health hazard to
humans. We also want to make the synthesis of chemicals as safe as possible, so the aim is
to avoid using hazardous chemicals as starting points if safer alternatives are available.
Additionally, having hazardous waste from chemical processes is something we want to
avoid, as this can cause problems with disposal.

5.2.4. Designing Safer Chemicals:

This principle links closely to the previous one. Chemists must aim to produce chemical
products that fulfil their role, be that medical, industrial, or otherwise, but which also have
minimal toxicity to humans. The design of safer chemical targets requires knowledge of
how chemicals act in our bodies and in the environment. In some cases, a degree of toxicity
to animals or humans may be unavoidable, but alternatives should be sought.

5.2.5. Safer Solvents & Auxiliaries:

Many chemical reactions require the use of solvents or other agents in order to facilitate
the reaction. They can also have a number of hazards associated with them, such as
flammability and volatility. Solvents might be unavoidable in most processes, but they
should be chosen to reduce the energy needed for the reaction, should have minimal
toxicity, and should be recycled if possible.

5.2.6. Design for Energy Efficiency:

Chemical companies should design their products to consume less energy to
decrease the overall environmental and economic impact. Green chemistry can
be achieved by using synthetic methods at ambient temperature and pressure.
Improving the green chemistry energy efficiency in the chemical manufacturing
process will reduce the dependency on fossil fuels. Energy-intensive processes are
frowned upon in green chemistry

5.2.7. Use of Renewable Feedstock:

The perspective of this principle is largely towards petrochemicals: products derived from
crude oil. These are used as starting materials in a range of chemical processes, but are non-
renewable, and can be depleted. Processes can be made more sustainable by using
renewable feedstock, such as chemicals derived from biological sources. Although the
concept of producing fuels and chemicals from feedstocks that never deplete
seems impracticable, it is not entirely impossible. This green chemistry principle
can become a reality due to developments in biotechnology, physics, agronomy,
toxicology, and engineering. As a result, in green chemistry it allows chemical
companies to use a renewable raw material or feedstock.

5.2.8. Reduce Derivatives:

Protecting groups are often used in chemical synthesis, as they can prevent alteration of
certain parts of a molecule’s structure during a chemical reaction, whilst allowing
transformations to be carried out on other parts of the structure. However, these steps
require extra reagents, and also increase the amount of waste a process produces. An
alternative that has been explored in some processes is the use of enzymes. As enzymes are
highly specific, they can be used to target particular parts of a molecule’s structure
without the need for the use of protecting groups or other derivatives.

5.2.9. Catalysis:

The use of catalysts can enable reactions with higher atom economies. Catalysts
themselves aren’t used up by chemical processes, and as such can be recycled many times
over, and don’t contribute to waste. They can allow for the utilization of reactions which
would not proceed under normal conditions, but which also produce less waste.

5.2.10. Design for Degradation:

Ideally, chemical products should be designed so that, once they have fulfilled their
purpose, they break down into harmless products and don’t have negative impacts on the
environment. Persistent organic pollutants are products which don’t break down and can
accumulate and persist in the environment; they are typically halogenated compounds,
with DDT being the most famous example. Where possible, these chemicals should be
replaced in their uses with chemicals that are more easily broken down by water, UV light,
or biodegradation

5.2.11. Real Time Pollution Prevention:

Monitoring a chemical reaction as it is occurring can help prevent release of hazardous and
polluting substances due to accidents or unexpected reactions. With real time monitoring,
warning signs can be spotted, and the reaction can be stopped or managed before such an
event occurs.

5.2.12. Safer Chemistry for Accident Prevention:

Working with chemicals always carries a degree of risk. However, if hazards are managed
well, the risk can be minimised. This principle clearly links with a number of the other
principles that discuss hazardous products or reagents. Where possible, exposure to
hazards should be eliminated from processes, and should be designed to minimise the risks
where elimination is not possible.

5.3. ATOM ECONOMY:

Atom economy (atom efficiency/percentage) is the conversion efficiency of a chemical
process in terms of all atoms involved and the desired products produced. Atom economy is
an important concept of green chemistry philosophy, and one of the most widely used metrics
for measuring the “greenness” of a process or synthesis.
Atom economy can be written as:

Atom = Molecular Weight of desired product X 100%
Economy Molecular Weight of all reactants

REACTANT 1 + REACTANT 2  PRODUCT + ANOTHER PRODUCT

For a multi-step process, where the intermediates are formed in one step and consumed
during a later step:
A+BC
C+DE

E+FG

Atom = Mr(G) X 100%

Economy Mr(A)+ Mr(B)+ Mr(D)+ Mr(F)

Atom economy is a different concern than chemical yield, because a high-yielding process
can still result in substantial by products. Examples include the Cannizzaro reaction, in which
approximately 50% of the reactant aldehyde becomes the other oxidation state of the
target; the Wittig reaction, which uses high-mass phosphorus reagents that ultimately
become waste; and the Gabriel synthesis, which produces a stoichiometric quantity of phthalic
acid.

If the desired product has an enantiomer the reaction needs to be
sufficiently stereoselective even when atom economy is 100%. A Diels-Alder reaction is an
example of a potentially very atom efficient reaction that also can be chemo-, regio-,
diastereo- and enantioselective. Catalytic hydrogenation comes the closest to being an ideal
reaction that is extensively practiced both industrially and academically.

Atom economy can also be adjusted if a pendant group is recoverable, for example Evans
auxilliary groups. However, if this can be avoided it is more desirable, as recovery processes
will never be 100%. Atom economy can be improved upon by careful selection of starting
materials and a catalyst system.

Poor atom economy is common in fine chemicals or pharmaceuticals synthesis, and especially
in research, where the aim to readily and reliably produce a wide range of complex
compounds leads to the use of versatile and dependable, but poorly atom-economical
reactions. For example, synthesis of an alcohol is readily accomplished by reduction of an
ester with lithium aluminium hydride, but the reaction necessarily produces a voluminous floc
of aluminium salts, which have to be separated from the product alcohol and disposed of.
The cost of such hazardous material disposal can be considerable. Catalytic hydrogenolysis
of an ester is the analogous reaction with a high atom economy, but it requires catalyst
optimization, is a much slower reaction and is not applicable universally.

5.4.Benefits of Green Chemistry:

Human health:

 Cleaner air: Less release of hazardous chemicals to air leading to less damage to
lungs

 Cleaner water: less release of hazardous chemical wastes to water leading to
cleaner drinking and recreational water

 Increased safety for workers in the chemical industry; less use of toxic materials;
less personal protective equipment required; less potential for accidents (e.g., fires
or explosions)

 Safer consumer products of all types: new, safer products will become available for
purchase; some products (e.g., drugs) will be made with less waste; some products
(i.e., pesticides, cleaning products) will be replacements for less safe products

 Safer food: elimination of persistent toxic chemicals that can enter the food chain;
safer pesticides that are toxic only to specific pests and degrade rapidly after use

 Less exposure to such toxic chemicals as endocrine disruptors

Environment:

 Many chemicals end up in the environment by intentional release during use (e.g.,
pesticides), by unintended releases (including emissions during manufacturing), or
by disposal. Green chemicals either degrade to innocuous products or are
recovered for further use

 Plants and animals suffer less harm from toxic chemicals in the environment
 Lower potential for global warming, ozone depletion, and smog formation
 Less chemical disruption of ecosystems
 Less use of landfills, especially hazardous waste landfills

Economy and business:

 Higher yields for chemical reactions, consuming smaller amounts of feedstock to
obtain the same amount of product

 Fewer synthetic steps, often allowing faster manufacturing of products, increasing
plant capacity, and saving energy and water

 Reduced waste, eliminating costly remediation, hazardous waste disposal, and
end-of-the-pipe treatments

 Allow replacement of a purchased feedstock by a waste product
 Better performance so that less product is needed to achieve the same function

 Reduced use of petroleum products, slowing their depletion and avoiding their
hazards and price fluctuations

 Reduced manufacturing plant size or footprint through increased throughput
 Increased consumer sales by earning and displaying a safer-product label. (e.g., safer

choice labelling)
 Improved competitiveness of chemical manufacturers and their customers

5.5. SYNTHESIS:

5.5.1. GREEN SYNTHESIS OF ADIPIC ACID

Adipic acid or hexanedioic acid is the organic compound with the formula (CH2)4(COOH)2.
From an industrial perspective, it is the most important dicarboxylic acid: about 2.5 billion
kilograms of this white crystalline powder are produced annually, mainly as a precursor for
the production of nylon. Adipic acid otherwise rarely occurs in nature, but it is known as
manufactured E number food additive E355.
The majority of the 2.5 billion kg of adipic acid produced annually is used as a monomer for
the production of nylon by a polycondensation reaction with hexamethylene diamine
forming 6,6-nylon. Other applications include some Polyurethanes. Esters of Adipic Acid,
such as DOA (Di-2-Ethylhexyl Adipate) are used as plasticizers for PolyVinyl Chloride (PVC)
resins.
Adipic acid has been incorporated into controlled-release tablets to obtain a pH-
independent release for both weakly basic and weakly acidic drugs. It has also been

incorporated into polymeric coatings of hydrophilic monolithic systems to modulate the pH,
resulting in zero-order release of a hydrophilic drug.

In foods, small but significant amounts of adipic acid are used as a food ingredient as a
flavorant and gelling aid. It is used in some calcium carbonate antacids to make them tart.

STRUCTURE OF ADIPIC ACID:

5.5.2. GREEN SYNTHESIS OF INDIGO

Indigo dye is an organic compound with a distinctive blue colour. Historically, indigo was
natural dye extracted from the leaves of certain plants, and this process was important
economically because blue dyes were once rare. A large percentage of indigo dye produced
today, several thousand tonnes each year, is synthetic. It is the blue often associated with
denim cloth and blue jeans. The primary use for indigo is as a dye for cotton yarn, which is
mainly for the production of denim cloth for blue jeans. On average, a pair of blue jean
pants requires 3–12 g of indigo. Small amounts are used for dyeing wool and silk.

Indigo carmine, or indigo, is an indigo derivative which is also used as a colorant. About 20
thousand tons are produced annually, again mainly for blue jeans. It is also used as a food
colorant, and is listed in the United States as FD&C Blue No. 2.

STRUCTURE OF INDIGO:

5.5.3. GREEN SYNTHESIS OF CARBARYL

Carbaryl (1-naphthyl methylcarbamate) is a chemical in the carbamate family used chiefly as
an insecticide. It is a white crystalline solid commonly sold under the brand name Sevin, a
trademark of the Bayer Company. Union Carbide discovered carbaryl and introduced it
commercially in 1958. Bayer purchased Aventis CropScience in 2002, a company that
included Union Carbide pesticide operations. It remains the third-most-used insecticide in
the United States for home gardens, commercial agriculture, and forestry and rangeland
protection. About 11 million kilograms were applied to U.S. farm crops in 1976. As a
veterinary drug, it is known as carbaryl (INN). The development of the carbamate
insecticides has been called a major breakthrough in pesticides. The carbamates do not
have the persistence of chlorinated pesticides. Although toxic to insects, carbaryl is
detoxified and eliminated rapidly in vertebrates. It is neither concentrated in fat nor
secreted in milk, so is favoured for food crops, at least in the US. It is the active ingredient in

Carylderm shampoo used to combat head lice until infestation is eliminated. Carbaryl kills
both targeted (e.g., malaria-carrying mosquitos) and beneficial insects (e.g., honeybees), as
well as crustaceans.

Although approved for more than 100 crops in the US, carbaryl is illegal in the United
Kingdom, Austria, Denmark, Sweden, Iran, Germany, and Angola.
Carbaryl is a cholinesterase inhibitor and is toxic to humans. It is classified as a likely human
carcinogen by the United States Environmental Protection Agency (EPA.) The oral LD is 250
to 850 mg/kg for rats and 100 to 650 mg/kg for mice.
Carbaryl can be produced using methyl isocyanate (MIC) as an intermediary. A leak of MIC
used in the production of carbaryl caused the Bhopal disaster, the most lethal industrial
accident in history.

STRUCTURE OF CARBARYL:

5.5.4. GREEN SYNTHESIS OF IBUPROFEN

Ibuprofen is a nonsteroidal anti-inflammatory drug (NSAID). It works by reducing hormones
that cause inflammation and pain in the body.
Ibuprofen is used to reduce fever and treat pain or inflammation caused by many conditions
such as headache, toothache, back pain, arthritis, menstrual cramps, or minor injury.
Ibuprofen is used in adults and children who are at least 6 months old.
Ibuprofen can increase your risk of fatal heart attack or stroke, especially if you use it long
term or take high doses, or if you have heart disease. Do not use this medicine just before or
after heart bypass surgery (coronary artery bypass graft, or CABG).
Ibuprofen may also cause stomach or intestinal bleeding, which can be fatal. These
conditions can occur without warning while you are using ibuprofen, especially in older
adults.

Do not take more than your recommended dose. An ibuprofen overdose can damage your
stomach or intestines. Use only the smallest amount of medication needed to get relief
from your pain, swelling, or fever.

STRUCTURE OF IBUPROFEN:

5.5.5. GREEN SYNTHESIS OF BENZIMIDAZOLE

Benzimidazole is a bicyclic heteroaromatic compound of fused benzene and imidazole.
Benzimidazoles are weakly basic in nature, slightly less basic than imidazoles, therefore they
are generally soluble in dilute acids. The pK value of benzimidazole was deduced a while ago
and found to be pKa1 = 5.30 and pKa2 = 12.3. Benzimidazoles are also sufficiently NH-acidic
to be generally soluble in aqueous alkali and form N-metallic compounds. The acidic
properties of the benzimidazoles, like those of the imidazoles [6], seem to be due to
stabilization of the ion by resonance. Benzimidazoles are distillable and can be distilled
unchanged above 300°C.

Benzimidazoles are often bioactive. Many anthelmintic drugs (albendazole, mebendazole,
triclabendazole, etc.) belong to the benzimidazole class of compounds. Benzimidazole
fungicides are commercialized. They act by binding to the fungal microtubules and stopping
hyphal growth. It also binds to the spindle microtubules and blocks nuclear division. In

printed circuit board manufacturing, benzimidazole can be used as an organic solderability
preservative.

Several dyes are derived from benzimidazoles.

STRUCTURE OF BENZIMIDAZOLE:

5.6. BIODIESEL

5.6.1. INTRODUCTION:

Biodiesel is a form of diesel fuel derived from plants or animals and consisting of long-
chain fatty-acid esters. It is typically made by chemically reacting lipids such as animal fat
(tallow), soybean oil, or some other vegetable oil with an alcohol, producing
a methyl, ethyl or propyl ester.

Unlike the vegetable and waste oils used to fuel converted diesel engines, biodiesel is
a drop-in biofuel, meaning it is compatible with existing diesel engines and distribution
infrastructure. Biodiesel can be used alone or blended with petrodiesel in any
proportions. Biodiesel blends can also be used as heating oil.

5.6.2.Advantages of biodiesel:

 Biodiesel fuel is a renewable energy source, unlike petroleum-based diesel.
 Biodiesel is less polluting than petroleum diesel.
 The lack of sulfur in 100% biodiesel extends the life of catalytic converters.
 Biodiesel can be blended with other energy resources and oil.
 Biodiesel fuel can be used in existing oil heating systems and diesel engines without

any alterations to those systems or engines.
 Biodiesel can be distributed through existing diesel fuel pumps, which is another

advantage over other alternative fuels.
 Sulfur, which acts as a lubricating agent, must be removed from conventional

petroleum-based diesel fuel. The lubricating property of biodiesel fuel can lengthen
the lifetime of engines.

5.6.3. Disadvantages of biodiesel:

 At present, biodiesel fuel is more expensive than petroleum diesel fuel.
 Biofuels are a solvent and therefore can harm rubber hoses in some engines.
 As a solvent, biodiesel cleans dirt from engines. This dirt can then get collected in

fuel filters, clogging them. As a result, filters have to be changed after the first
several hours of biodiesel use.

 Biodiesel fuel distribution infrastructure needs improvement to make biodiesel more
widely available.

 In cold weather, pure biodiesel can thicken or gel, making it hard to pump.





HERE’S A SMALL QUIZ:

1. The first listed of the 12 Principles of Green Chemistry is?

a) Prevent waste

b) Catalysis

c) Atom economy
d) Benign solvents
2. Which of the following is the greenest solvent?

a) Formaldehyde

b) Benzene
c) Ethanol

d) Water
3. Environmental benefits of green chemistry include?

a) Fewer raw materials and natural resources used
b) Cleaner production technologies & reduced emissions
c) Smaller quantities of hazardous waste to be treated and disposed of
d) All of the above
4. The following legislation gave birth to today's green chemistry initiatives?

a) Clean Water Act of 1972

b) Montreal Protocol of 1989

c) Pollution Prevention Act of 1990

d) Superfund Act of 1980

5. _ is an excellent ‘green’ solvent as well as a greenhouse gas?

a) Methanol

b) CFCs

c) Carbon monoxide

d) Carbon Dioxide

Q.NO: 1 2 3 4 5
ANS: a d d c d

5.7 GREEN COMPUTING

5.7.1. INTRODUCTION:

Green computing refers to environmentally sustainable computing. It minimizes the use of
electricity as well as energy and reduce the environmental dissipate when we are using a
computer. The green computing has the same goals with green chemistry, which is longer
the life time of the product and makes the product more efficiency of energy, advance the
discarded product and factory waste to be more easily recycled and biodegradable, use of
the less-hazardous materials.

According to San Murugesan, green computing is the study of designing, manufacturing,
using, and disposing of computers, servers, and related subsystems-such as monitors,
printers, storage devices, and networking and communications systems which is efficiently
and effectively with minimal or no impact on the environment. It also strives to get
economic achievability and better system performance and use due to abide your social and
ethical responsibilities. In the economic sense, it has efficiency energy, a save the total cost
of ownership, which includes the cost of disposal and recycling. Therefore it is the study and
practice of using computing resources efficiently.

5.7.2 Origin:

The labeling program which is known as Energy Star was one of the earliest initiatives
toward in United States. In 1992, the Environmental Protection Agency (EPA) started to
promote all kinds of hardware of energy efficiency, also climate control equipment, and
other technologies and it was regarded as Energy Star. The label of Energy Star became a
general sight, mainly in notebook computers and displays. In Europe and Asia, similar
programs have also been implemented. The sleep mode is then adopted among consumer
electronics. After the Energy Star program began, the term “green computing” was probably
invented shortly.

5.7.3 Pathways to Green Computing:

In accordance with San Murugesan, the study of green computing which is related to use,
disposal, designing, and manufacturing, here are the elaborations of the above.
There are ways to achieve green computing, aim to make the whole IT lifecycle greener. The
following four complementary paths dealing with environmental sustainability are:

 Green use. Using computers and other information systems in an environmentally
sound manner such as reduce the energy consumption.

 Green disposal. When dealing unwanted computers or electronic equipment, recycle
them properly. Old computers are also encouraged to be reuse or refurbished.

 Green design. Designing energy-efficient and environmentally sound components,
computers, servers, cooling equipment, and data centres

 Green manufacturing. Manufacturing electronic components, computers, and other
associated subsystems with minimal impact on the environment.

5.7.4. Importance of Green Computing:

Why should we have the idea of green computing?
When the news claimed that the environment was not a renewable resource, it really hit
home and people started realizing that they had to do their part to protect the
environment. Therefore, green computing is an important idea to keep our environment
clean and safe. When it gets involved in recycling computer, it is difficult to dispose the old
computers and some more that they take up much space in landfills. Somehow, the
problem is that the electronic waste is increasing tremendously within this decade. Many
negative effects are gradually showed up towards this environment, especially to human.
Due to the quick obsolescence of electronics, it resulted a dreadful 70% of all hazardous
waste. Computer waste is high in many toxic materials such as heavy metals and flame-

retardant plastics, which easily leach into ground water and bio-accumulate. In addition, to
manufacture chips of the electronic requires huge amounts of resources and some deadliest
gases and chemicals are used to man. In an average year, 24 million computers have
become obsolete in United States. Only about 14% (3.3 million) of these will be recycled or
donated. Over 20 million computers, the rest in U.S. will be get rid of, destroyed or shipped
as waste products or to be dealt with later in the temporary storage. We do not care about
what happens when our laptop dies and just stop to consider it. The reality is that it either
decomposed in a landfill or developing countries. The children there wrestling its
components apart by hand and melting toxic bits to discover traces or valuable metals like
gold.Moreover, E-Waste trade chain is created in developing nations for the imported
obsolete electronics. They employ several workers, collectors, segregators, middlemen,
scrap dealers and recyclers to take components apart, reuse the functional components,
burning or acid dipping and other unprofessional techniques to recycle the non-functional
components. After burning and other wastes are disposed, the spent acids and other
chemicals, solid wastes eventually end up in rivers. This resulted serious problem of
pollution of water, the source we depend , which can threaten our lives

5.7.5. Recommendation:

We should take our responsibility to reduce the environmental impact of computing in
order to keep our planet clean and healthy. As users, we could do our part by altering our
habits. Here are the ways we can make our world better if we: using computers and devices
that comply with the Energy Star program, telecommuting instead of travelling by planes
or ship, using paperless method to communicate or in business. In my opinion, technology
is created and improved in our generation is to upgrade our quality of life. We should
appreciate this advantage but not misuse it. If we waste our resources restlessly and there
will not be any chances for us to repent and our live seems to reach the end. Because of the
non-renewable resource, which is a natural resource, such as fossil fuel, cannot sustain in a
long time if we use them without conservation. This is because the resources often existed
in fixed amount, and we keep consuming that much faster than the nature can create
them. We use them in our daily life, how would it be if we run out of petroleum? No
transport, no food, economic crisis. More disasters will happen with unexpectedly fast.
Therefore, we can change our attitudes now as long as we still have chance to live. In
addition, we have only one earth, so treat it well!

5.7.6. Conclusion:

To come to our knowledge, the man-made greenhouse gas emissions increasing is a major
contributing factor to global warming, enterprises, governments, and also our society. In
the mean time, people trying to tackle environmental issues and adopting environmentally
to live in harmony and peacefully with this earth. Therefore, greening our IT products,
applications, services and practices are both economic and environmental essential, as
well as our social responsibility. As a result, a growing number of IT vendors and users are
moving toward green computing and thereby assisting in building a green society and
economy. Through the effort of developing sustainable energy, we can create a better
quality of life for the coming generation. We can put our effort to learn more about
knowledge of computer disposal to protecting the environment. By green computing

technology, we are trying to make the whole process surrounding computers more friendly
to the environment, economy, and society.

5.8. CONCLUSION:

Green chemistry has come a long way since its birth in 1991 growing from a small idea into a new
approach to deal with environmental protection. All over the world, governments and industries are
working with green chemists for the betterment of our society. Green chemistry is the best practice
to avoid or minimize the potential risk of chemical disaster as well as to avoid or minimize the loss
of environment. Green chemistry is not a complete solution to all our environmental problems but
it is definitely a fundamental approach in solving most of our problems and also reducing pollution
to a great extent. The ultimate aim of green chemistry to entirely cut down the stream of
chemicals pouring into the environment. This aim seems unattainable at present, but progress in
the green chemical research areas and their application through successive approaches will certainly
provide safer speciality chemicals and much more satisfactory processes for the chemical industry.
Green chemistry is multi-faceted discipline that has been created as a contribution of chemistry to
sustainable development, avoiding damage to the environment. Obviously, the concern is greater
in the industry, since social alarm and legislative limitation have a more direct impact in this case.
Various panels from the industry have clearly outlined directions that should be followed. Thus,
important themes are not limited to the various aspects of synthesis and purification, but involve a
more complete survey. The final aim is putting a new product on the market only after this has
been proven the (environmentally) correct decision. In order to open new perspectives, the use of
renewable materials and energy must progress at the same time. The academic community
appears to consider synthesis as the most important theme, more example than the environmental
behaviour of the synthesized material. For this reason, the postulates of green chemistry have
permeated catalysis and, in part, organic chemistry. Reports of “new” syntheses are by far the main
component of the literature identified as green chemistry. Nevertheless, many of the papers
considered involve only partial results. These usually lack the early consideration of all the
environmentally relevant aspects that should be peculiar of this discipline, as well as any attention to
the engineering perspective of scaling up. This notwithstanding, one can certainly recognize a trend

imparted by the popularity of green chemistry postulates. As a consequence, chemists pay a greater
attention to the optimization of catalysis, to the elimination of toxic reagents and to the limitation or
elimination of solvents (much less to the use of “alternative” physical methods). In addition, many
preparative papers include an environmental assessment of the considered processes. If not
immediately, in the long range this work will certainly contribute also to the industrial development.

5.9. SOLVED NUMERICALS:-

1. What is the atom economy of producing Carbon-di-oxide by burning Propane?
C3H5 + 5O2 3CO2 + 4H2O

Ans. Desired Product MR = 3 (12 + 2 x 16) = 132
Reactants MR = 3 x 12 + 8 x 1 + 5(2 x 16) = 204

Atom = Molecular Weight of desired product X 100%
Economy Molecular Weight of all reactants
= 13200/204 = 64.7059%
2. Calculate the atom economy of ethanol produced by the fermentation of glucose:

C6H12O6 → 2C2H5OH + 2CO2

Ans. Desired Product MR = 2 (2 x 12 + 6 x 1 + 16) = 92
Reactants MR = 6 x 12 +12 x 1 + 6 x 16 = 180
Atom = Molecular Weight of desired product X 100%
Economy Molecular Weight of all reactants
= 9200/180 = 51.1111%

5.10. UNSOLVED NUMERICALS:- reduction of iron

1. What is the atom economy for iron produced by
oxide in blast furnace?

Fe2O3 + 3CO  2Fe + 3CO2

(Ans. 45.835)

2.What is the atom economy for cinnamaldehyde produced by mixing benzaldehyde and
acetaldehyde? (Ans. 88)

3.Calculate the % Atom economy for the following reaction with respect to allyl chloride.

CH3CH=CH2 + Cl2 → Cl-CH=CH2 + HCl (Ans. 67.69%)

4. Calculate the % Atom economy for the following reaction with respect to acetanilide.

C6H5NH2 + (CH3CO)2O → C6H5NHCOCH3 + CH3COOH

(Ans. 69.23)

5.Calculate the % Atom economy for the following reaction

CH3NH2 + COCl2 → CH3N=C=O + 2HCl (Ans. 43.84)

6.Calculate the % Atom economy for the following reaction

C6H6 + CH3COCl → C6H5CCOCH3 + HCl (Ans. 76.67)

7.Calculate the % Atom economy for the following reaction

CH3CH=CH2 + H2 → CH3CH2CH3 (Ans. 100)

8. Calculate the % Atom economy for the following reaction

C6H6 + Cl2 → C6H5Cl + HCl (Ans. 75.5)

9. Calculate the % Atom economy for the following reaction

C6H5NH2 + C6H5COCl → C6H5NHCOC6H5 + HCl

(Ans. 82.23)

5.11. SHORT QUESTIONS

1. What is green chemistry?
2. What is concept of atom economy?
3. What is the alternative solvent?
4. Name any two non-green solvents.

5. Name any two green solvents.
6. What is super critical co2? why is it considered a green solvent?
7. Biodiesel is an example of which of 12 principles of green chemistry.
8. Explain in detail the conventional and green route of manufacturing of benz-imidazole.
9. Iron is extracted from its core using carbon:

2fe2o3 + 3c → 4fe + 3co2
what is the atom economy of this reaction?
10. Explain why using reaction with high atom economy is important for sustainable
development.
11. Give the reaction of “trans esterification”. mention why is it required?
12. Explain “design for energy efficiency” principle of green chemistry.

5.12. LONG QUESTIONS

1. What are the goals of green chemistry?
2. What are benefits of green chemistry to human health?
3. State the 12 principles of green chemistry and write a few lines about each.
4. Write the synthesis for the following:

a) ibuprofen
b) adipic acid
5. Write in brief about biodiesel.
6. What are advantages and disadvantages of biodiesel.
7. Write a short note on green computing.
8. Why is it essential to design safer chemicals and products w.r.t to green chemistry
principle. explain in detail with an example.
9. Give an example to explain why it is beneficial to prevent waste formation in chemcial
process rather than treat waste.

10. The key reaction in the haber process for making ammonia is :
N2 + 3H2 → 2NH3

what is the atom economy of this reaction?
11. Explain basic ideas in the field of green chemistry research with the help of synthesis of
indigo dye.
12.” prevention of waste” is an important principle of green chemistry. explain.

REFERENCES:

SITES:

https://greenchemistry.yale.edu/about/history-green-chemistry
https://en.wikipedia.org/wiki/Paul_Anastas
https://greenchemistry.yale.edu/about/history-green-chemistry
https://www.epa.gov/greenchemistry/basics-green-chemistry
https://www.acs.org/content/acs/en/greenchemistry/principles/12-principles-of-green-
chemistry.html
https://www.compoundchem.com/2015/09/24/green-chemistry/
https://www.sigmaaldrich.com/chemistry/greener-alternatives/green-chemistry.html
https://www.greencentrecanada.com/green-chemistry/the-12-principles-of-green-
chemistry/
https://www.epa.gov/greenchemistry/benefits-green-chemistry
https://www.degruyter.com/view/journals/psr/2/8/article-20170051.xml
https://en.wikipedia.org/wiki/Biodiesel
https://afdc.energy.gov/files/pdfs/30882.pdf
https://whitelabelitsolutions.com/meaning-green-computing/
https://searchdatacenter.techtarget.com/definition/green-computing
https://www.pugetsound.edu/about/offices-services/technology-services/green-
computing/
-https://thechemco.com/chemical/adipic-acid/

https://www.drugs.com/ibuprofen.html

https://www.sciencedirect.com/topics/chemistry/benzimidazole

https://www.google.com/url?sa=i&url=https%3A%2F%2Fpresentationtube.com%2Fw%2F%
3Fv%3D9d5gsj8hbpo&psig=AOvVaw0HIWOoBoM4RytTeBAQHeRH&ust=1586179810508000
&source=images&cd=vfe&ved=0CAIQjRxqFwoTCOjo7rCy0egCFQAAAAAdAAAAABA1

BOOKS:

ENGINEERING CHEMISTRY (16TH EDITION BY-JAIN AND JAIN)

ENGINEERING CHEMISTRY (BY-DARA)

GREEN CHEMISTRY-ENVIRONMENT FRIENDLY ALTERNATIVES (BY-RASHMI SINGH, MM
SRIVASTAVA)

GREEN CHEMISTRY (BY- V.K. AHLUWALIA)

6. FUELS and COMBUSTION

6.1 INTRODUCTION –

The first known use of fuel was the combustion of wood or sticks by homo erectus nearly
two million years ago. Throughout most of human history only fuels derived from plants or
animal fat were used by humans. Charcoal, a wood derivative, has been used since at least
6,000 BCE for melting metals. It was only supplanted by coke, derived from coal, as
European forests started to become depleted around the 18th century. Charcoal briquettes
are now commonly used as a fuel for barbecue cooking.

Crude oil was distilled by Persian chemists, with clear descriptions given in Arabic handbooks
such as those of Muhammad ibn Zakariya Razi. He described the process of distilling crude
oil/petroleum into kerosene, as well as other hydrocarbon compounds, in his Kitab al-
Asrar (Book of Secrets). Kerosene was also produced during the same period from oil
shale and bitumen by heating the rock to extract the oil, which was then distilled. Razi also
gave the first description of a kerosene lamp using crude mineral oil, referring to it as the
"naffatah".

With the energy in the form of chemical energy that could be released
through combustion, but the concept development of the steam engine in the United
Kingdom in 1769, coal came into more common use as a power source. Coal was later used
to drive ships and locomotives. By the 19th century, gas extracted from coal was being used
for street lighting in London. In the 20th and 21st centuries, the primary use of coal is to
generate electricity, providing 40% of the world's electrical power supply in 2005.

Fossil fuels were rapidly adopted during the Industrial Revolution, because they were more
concentrated and flexible than traditional energy sources, such as water power. They have
become a pivotal part of our contemporary society, with most countries in the world
burning fossil fuels in order to produce power.

Currently the trend has been towards renewable fuels, such as biofuels like alcohols.

6.1.1 Definition –

A substance that produces useful energy when it undergoes a chemical or nuclear
reaction. Fuel such as coal, wood, oil, or gas provides energy when burned. Compounds in
the body such as glucose are broken down into simpler compounds to provide energy for
metabolic processes. A fuel is any material that can be made to react with other
substances so that it releases chemical or nuclear energy as heat or to be used for work.
In the combustion process, a fuel reacts with oxygen and releases the energy.

Fuel + O2 → CO2 +H2O + heat

6.2 CLASSIFICATION OF FUELS –

Fuels are classified according to their occurrence an state of aggregation. According to
occurrence they are classified as primary(natural) and secondary(derived) fuels and based
on the state of aggregation solid, liquid, and gaseous fuels.

Fuel
(occurance)

PRIMARY SECONDARY
(natural) (derived)

SOLID LIQUID GASEOUS SOLID LIQUID GASEOUS
(wood, (petroleum (natural (coke, semi (gasoline, (coal gas
peat, coal or crude oil) gases) diesel oil, water gas
,lignite) coke, kerosene) producer,
charcoal,
petroleum, LPG)
thiokol)

6.3 Characteristics of good fuel –

An ideal fuel should have the following properties:
(1) High calorific value: The amount of heat released depends on high calorific value, hence
fuel should possess more HCV
2) Moderate ignition temperature: Minimum required temperature to preheat the fuel and
start burning is the ignition temperature, because low ignition temperature is dangerous for
storage and transport due to fire hazard and for starting a fire, high ignition temperature is
not suitable
3) Low moisture content: Moisture content of fuel reduces the calorific value, hence fuel
should possess low moisture content.
4) Low Non-combustible matter: After combustion, non-combustible matter produces high
ash content and also reduces the heating value. With this more heat loss, and loss of money
for over storage, handling, disposal of ash, etc.

5) Moderate velocity of combustion: For continuous supply of heat, fuel must burn with
moderate velocity.
6) Low cost and Easy to transport: Good fuel should be easily available in bulk at low cost
and easy to transport.

Units of heat –

As a form of energy, heat has the unit joule (J) in the International System of units (SI).
However, in many applied fields in engineering the British thermal unit (BTU) and
the calorie are often used. The standard unit for the rate of heat transferred is the watt (W),
defined as one joule per second.

Use of the symbol Q for the total amount of energy transferred as heat is due to Rudolf
Clausius in 1850:

"Let the amount of heat which must be imparted during the transition of the gas in a
definite manner from any given state to another, in which its volume is v and its
temperature t, be called Q"

Heat released by a system into its surroundings is by convention a negative quantity
(Q < 0); when a system absorbs heat from its surroundings, it is positive (Q > 0). Heat
transfer rate, or heat flow per unit time, is denoted by Q.. This should not be confused
with a time derivative of a function of state (which can also be written with the dot
notation) since heat is not a function of state. Heat flux is defined as rate of heat
transfer per unit cross-sectional area (units watts per square metre).

6.4 Calorific Value –

The heating value (or energy value or calorific value) of a substance, usually a fuel or food,
is the amount of heat released during the combustion of a specified amount of it.

The calorific value is the total energy released as heat when a substance undergoes
complete combustion with oxygen under standard conditions. The chemical reaction is
typically a hydrocarbon or other organic molecule reacting with oxygen to form carbon
dioxide and water and release heat. It may be expressed with the quantities:

• energy/mole of fuel
• energy/mass of fuel
• energy/volume of the fuel

There are two kinds of heat of combustion, called higher and lower heating value,
depending on how much the products are allowed to cool and whether compounds
like H2O are allowed to condense. The values are conventionally measured with a bomb
calorimeter. They may also be calculated as the difference between the feat of
formation ΔH⦵f of the products and reactants (though this approach is somewhat artificial
since most heats of formation are calculated from measured heats of combustion). For a
fuel of composition CcHhOoNn, the (higher) heat of combustion is 418 kJ/mol (c + 0.3 h –
0.5 o) usually to a good approximation (±3%), though it can be drastically wrong
if o + n > c (for instance in the case of nitroglycerin (C3H5N3O9) this formula would predict a
heat of combustion of 0). The value corresponds to an exothermic reaction (a negative
change in enthalpy) because the double bond in molecular oxygen is much weaker than

other double bonds or pairs of single bonds, particularly those in the combustion products
carbon dioxide and water; conversion of the weak bonds in oxygen to the stronger bonds
in carbon dioxide and water releases energy as heat.

By convention, the heat of combustion is defined to be the heat released for the complete
combustion of a compound in its standard state to form stable products in their standard
states: hydrogen is converted to water (in its liquid state), carbon is converted to carbon
dioxide gas, and nitrogen is converted to nitrogen gas. That is, the heat of combustion,
ΔH°comb, is the heat of reaction of the following process:

CxHyNzOn (std.) + O2 (g, xs.) → xCO2 (g) + y⁄2H2O (l) + z⁄2N2 (g)

Chlorine and sulfur are not quite standardized; they are usually assumed to convert to
hydrogen chloride gas and SO2 or SO3 gas, respectively, or to dilute aqueous
hydrochloric and sulfuric acids, respectively, when the combustion is conducted in a
bomb containing some quantity of water.

6.4.1 Gross or Higher Calorific Value –

The quantity known as higher heating value (HHV) (or gross energy or upper heating
value or gross calorific value (GCV) or higher calorific value (HCV)) is determined by
bringing all the products of combustion back to the original pre-combustion temperature,
and in particular condensing any vapor produced. Such measurements often use a standard
temperature of 25 °C (77 °F; 298 K)]. This is the same as the thermodynamic heat of
combustion since the enthalpy change for the reaction assumes a common temperature of
the compounds before and after combustion, in which case the water produced by
combustion is condensed to a liquid. The higher heating value takes into account the latent
heat of vaporisation of water in the combustion products, and is useful in calculating heating
values for fuels where condensation of the reaction products is practical (e.g., in a gas-
fired boiler used for space heat). In other words, HHV assumes all the water component is in
liquid state at the end of combustion (in product of combustion) and that heat delivered at
temperatures below 150 °C (302 °F) can be put to use.

6.4.2 Net or Lower Calorific Value –

The quantity known as net calorific value (NCV) or lower calorific value (LCV) is determined
by subtracting the heat of vaporisation of the water from the higher heating value. This
treats any H2O formed as a vapor. The energy required to vaporize the water therefore is
not released as heat.

LHV calculations assume that the water component of a combustion process is in vapor
state at the end of combustion, as opposed to the higher heating values (HHV) (a.k.a. gross
calorific value or gross CV) which assumes that all of the water in a combustion process is in
a liquid state after a combustion process.

The LHV assumes that the latent heat of vaporization of water in the fuel where
condensation of the combustion products is impractical, or heat at a temperature below
150 °C (302 °F) cannot be put to use.

The enthalpy of all combustion products minus the enthalpy of the fuel at the reference
temperature (API research project 44 used 25 °C. GPSA currently uses 60 °F), minus the

enthalpy of the stoichiometric oxygen (O2) at the reference temperature, minus the heat of
vaporization of the vapor content of the combustion products.
The distinction between the two is that this second definition assumes that the combustion
products are all returned to the reference temperature and the heat content from the
condensing vapor is considered not to be useful. This is more easily calculated from the
higher heating value than when using the preceding definition and will in fact give a slightly
different answer.

FORMULA -

NCV = GCV – latent heat of water vapours formed

= GCV – (9*H/100 * latent heat of steam)

GCV – 0.09H * 587 kcal/kg

6.5 Dulong’s formulae –

If we know the ultimate analysis of fuel, we can easily calculate its GCV.
The basic principle is that there are only 3 components in a fuel which generate heat. These
are:
Carbon, Hydrogen and Sulphur.
According to Dulong's formula,
Calorific value of carbon = 8080 kcal/kg
Calorific value of hydrogen = 34500 kcal/kg
Calorific value of sulphur = 2240 kcal/kg
gross calorific value of a fuel is;
GCV = 1/100[8080C + 34500(H-O/6) + 2240S]
Each multiple of carbon, hydrogen and sulphur represents heat generated by its one mole.
The formula gives GCV in kcal/kg.

6.6 Solid fuel:-

Solid fuel refers to various forms of solid material that can be burnt to release energy,
providing heat and light through the process of combustion. Solid fuels can be contrasted
with liquid fuels and gaseous fuels. Common examples of solid fuels include wood, charcoal,
peat, coal, Hexamine fuel tablets, wood pellets, corn, wheat, rye, and other grains. Solid
fuels are extensively used in rocketry as solid propellants. Solid fuels have been used
throughout human history to create fire and solid fuel is still in widespread use throughout
the world in the present day.

6.7 Types of solid fuels-

Wood fuel:

Wood fuel can refer to several fuels such as firewood, charcoal, wood chips
sheets, pellets, and sawdust . Today, burning of wood is the largest use of
energy derived from a solid fuel biomass. Wood fuel can be used for cooking
and heating, and occasionally for fueling steam engines and steam turbines
that generate electricity.

Biomass:

Although wood is a form of biomass, the term usually refers to other
natural plant material that can be burnt for fuel. Common biomass fuels
include waste wheat, straw, nut shells and other fibrous material.

Peat:

Peat fuel is an accumulation of partially decayed vegetation or organic matter
that can be burnt once sufficiently dried.

Coal:

Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock
strata in layers or veins called coal beds or coal seams. Coal is the largest source of energy
for the generation of electricity worldwide, as well as one of the largest worldwide
anthropogenic sources of carbon dioxide releases. The extraction of coal, its use in energy
production and its by products are all associated with environmental and health effects
including climate change. Variations such as smokeless coal can be formed naturally in the
form of anthracite, a metamorphosed type of coal with a very high carbon content that
gives off a smokeless flame when set alight.

Coke:

Coke is a fuel with few impurities and a high carbon content, usually made from coal. It is
the solid carbonaceous material derived from destructive distillation of low-ash, low-sulfur
bituminous coal. Cokes made from coal are grey, hard, and porous. While coke can be
formed naturally, the commonly used form is man-made. The form known as petroleum
coke, or pet coke, is derived from oil refinery coker units or other cracking processes.

Municipal waste:

Municipal solid waste commonly known as trash or garbage in the United States and as
rubbish in Britain, is a waste type consisting of everyday items that are discarded by the
public. With the correct technology it can be gasified and converted to a viable fuel source.
However, this is technology heavy and can only be used where the waste is known not to
contain toxic materials.

Rocket propellant:

Solid rocket propellant consists of a solid oxidizer (such as ammonium nitrate) bound with
flakes or powders of energy compounds (such as RDX) plus binders, plasticizers, stabilizers
and other additives. Solid propellant is much easier to store and handle than liquid
propellant. It also has a higher energy density so it does not require as large of a space for
the same amount of stored energy.

Environmental impact of the coal industry -

Solid fuels, compared to liquid fuels or gaseous fuels, are often cheaper, easier to extract,
more stable to transport and in many places are more readily available. Coal, in particular,
is utilized in the generation of 38.1% of the world’s electricity because it is less expensive
and more powerful than its liquid and gas counterparts. However, solid fuels are also
heavier to transport, require more destructive methods to extract/burn and often have
higher carbon, nitrate and sulphate emissions. With the exception of sustainable
wood/biomass solid fuel is normally considered non-renewable as it requires thousands of
years to form.

6.8 Coal: -

Coal, one of the most important primary fossil fuels, a solid carbon-rich material that
is usually brown or black and most often occurs in stratified sedimentary deposits.
Although most coals occur in stratified sedimentary deposits, the deposits may later be
subjected to elevated temperatures and pressures caused by igneous intrusions or
deformation during orogenesis (i.e., processes of mountain building), resulting in the
development of anthracite and even graphite. Although the concentration of carbon in
Earth’s crust does not exceed

0.1 percent by weight, it is indispensable to life and constitutes humankind’s main
source of energy.