Unit XIV : Environmental Chemistry

Content of UNIT XIV: Environmental Chemistry

• Introduction to Environment and Environmental Chemistry

• Introduction to Pollution in different Environment and Ecosystems….

Air or Atmosphere Water Soil

• Chemical reactions in Atmosphere…. Smogs Major Atmospheric Pollutants Acid rain Ozone depletion Greenhouse effect and global warming

• Green Chemistry as an alternative tool for reducing pollution

•Strategy for control of Environmental Pollution

• The term environment has been derived from a French word “Environia” meaning “surroundings”.

• It refers to both biotic (living) and abiotic (physical or non-living) materials in which organisms live.

• Environment regulates the life of the organisms including human beings.

• Ordinarily environment refers to the materials and forces that surrounds the living organism.

• It is comprised of the interacting systems of physical, biological and elements which are interlinked both individually and collectively.

Meaning, Definition and Components of Environment

An ecosystem is a network of interactions among organisms, and between organisms and their environment.

Components of Environment

• Environment mainly consists of Atmosphere, Hydrosphere, Lithosphere and Biosphere.

• It is divided into two types such as (a) Micro environment and (b) Macro environment.

• It can also be divided into two other types such as (c) Physical and (d) biotic environment.

• Physical environment refers to all abiotic factors or conditions like temperature, light, rainfall, soil, minerals etc. It comprises of atmosphere, lithosphere and hydrosphere.

• Biotic environment includes all biotic factors or living forms like plants, animals, Micro-organisms.

•Environmental chemistry is the scientific study of the chemical and biochemical phenomena that occur in natural Environment.

•It can be defined as the study of the sources, reactions, transport, effects, and fates of chemical species in the air, soil, and water environments due to anthropogenic activity and biological activity.

•The impacts may be felt on a local scale, through the presence of pollutants or toxic substances arising from a chemical waste site, or on a global scale as global warming.

Environmental Chemistry: Definition

Environmental Pollution: Definition

• Environmental pollution is the effect of undesirable changes in environment due to introduction of contaminants that have harmful effects on plants, animals and human beings.

• A substance, which causes pollution, is known as “pollutant”. Where as, “contaminant” is pollutant causes irreversible damage or lethal effect to air, water, soil and biotic communities.

• Pollutants can be solid, liquid or gaseous substances present in greater concentration and are produced due to human activities or natural happenings.

• Pollutants which are slowly degradable, remain in the environment in an unchanged form for many decades. Substances such as dichlorodiphenyltrichloroethane (DDT), plastic materials, heavy metals, many chemicals, nuclear wastes etc.,

• Environmental pollution, pollutants originate from a source and get transported by air or water or are dumped into the soil by human beings.

Environmental Pollution

• Pollution has seen since the onset of the industrial revolution during the 19th century.

• Technological progress facilitated by super efficiency, overproduction, overconsumption are main causes of serious deterioration of natural resources.

• Environmental pollution is a problem both in developed and developing countries. Factors such as population growth and urbanization cause the use of natural resources to the maximum.

Classification of Environmental Pollution 

Pollution can be broadly classified according to the components of environment that are polluted.

Major of these are: Air or Atmospheric pollution , Water pollution, Soil pollution (land degradation), Industrial pollution etc.,

Pollutants are generally grouped under two classes:

• Biodegradable pollutants – Biodegradable pollutants are broken down by the activity of micro-organisms and enter into the biogeochemical cycles. Ex: domestic waste products, sewage, agricultural residue, paper, wood etc.,

• Non- Biodegradable pollutants – Non-biodegradable pollutants are stronger chemical bondage, do not break down into simpler and harmless products. Ex:- pesticides, Heavy Metals, plastics, radioactive waste etc.

Types of Pollution

Atmospheric or Air Pollution

• Definition: Air pollution is the introduction of particulates other harmful substances such as gases into Earth's atmosphere. Air pollution may come from anthropogenic or natural sources.

• The pollutant can be solid particles, liquid droplets, or gases.

• Air pollutants are classified as primary or secondary.

• Primary pollutants are usually produced from a process, such as ash from a volcanic eruption, carbon monoxide gas from motor vehicle exhaust, or the sulfur dioxide and NOX released from factories.

• Secondary pollutants are not emitted directly. they form in the air when primary pollutants react or interact. Ex:-ozone, NO2 and NOX.

How atmospheric pollution is caused?• Most of this air pollution results from the burning of fossil fuels (CO2

emission), such as coal, oil, natural gas, and gasoline to produce electricity and power our vehicles.

Types Atmosphere•The atmosphere that surrounds the earth is not of the same thickness at all heights. There are concentric layers of air and each layer has different density. They are… Troposphere and StratosphereTroposphere• The lowest region of atmosphere in

which the human beings along with other organisms live. It extends up to the height of ~ 10 km from sea level.

• This is the region of strong air movement and cloud formation.

StratosphereIt lies between 10 and 50 km above sea level. It contains dinitrogen (N2), dioxygen (O2), ozone and little water vapour.

• Atmospheric pollution is generally studied as tropospheric and stratospheric pollution.

• The presence of ozone in the stratosphere prevents about 99.5% of the sun’s harmful ultraviolet (UV) radiations from reaching the earth’s surface.

• Protecting humans and other animals from its effect.

Tropospheric pollution occurs due to the presence of undesirable solid or gaseous particles in the air. The following are the major gaseous and particulate pollution in the air.

Gaseous air pollutants: These are oxides of sulphur, nitrogen and carbon, hydrogen sulphide, hydrocarbons, ozone and other oxidants.

Particulate pollutants: These are dust, mist, fumes, smoke, smog etc.,

Tropospheric pollution

Oxides of Sulphur • Oxides of sulphur are produced when

sulphur containing fossil fuel is burnt. The most common oxide among them is sulphur dioxide.

Harmful effects of sulphur dioxide :

• This gas is poisonous for living organisms and asthma, bronchitis and emphysema in humans.

• In plants, a high concentration of sulphur dioxide makes the flower buds stiff and makes them fall off, hampering its reproductive cycle.

2SO2(g) + O2(g) → 2SO3(g)

SO3 (g)+H2O(l) → H2SO4(aq)

• Sulphur dioxide is the main component in killer smog.• The presence of particulate matter in polluted air catalyses the

oxidation of sulphur dioxide to sulphur.

Oxides of Nitrogen

• Mixture of gases that are composed of nitrogen and oxygen. At high altitudes when lightning strikes, they combine to form oxides of nitrogen.

• Two of the most toxicologically significant compounds are nitric oxide (NO) and nitrogen dioxide (NO2).

• Other gases belonging to this group are nitrogen monoxide (NO) nitrous oxide, N2O, and nitrogen pentoxide (NO5).

N2 (g) + O2 (g) → 2NO(g)⎯NO reacts instantly with oxygen to give NO2

2NO (g) + O2 (g) → 2NO2 (g)

Rate of production of NO2 is faster when nitric oxide reacts with ozone in the stratosphere.NO (g) + O3 (g) → NO2 (g) + O2 (g)

Harmful effects of Nitrogen oxides compounds

• The irritant red haze in the traffic and congested places is due to oxides of nitrogen.

• Higher concentrations of NO2 damage the leaves of plants and retard the rate of photosynthesis.

• Nitrogen dioxide NO2 is a lung irritant that can lead to an acute respiratory disease in children.

Hydrocarbons are composed of hydrogen and carbon only and are formed by incomplete combustion of fuel used in automobiles.

Hydrocarbons are carcinogenic, i.e., they cause cancer.

They harm plants by causing ageing, breakdown of tissues and shedding of leaves, flowers and twigs.

Hydrocarbons

Oxides of Carbon or Oxocarbon

• An oxocarbon or oxide of carbon is a chemical compound consisting only of carbon and oxygen.

• Carbon forms two well-known oxides, Carbon monoxide (CO) and Carbon dioxide (CO2). In addition, it also forms Carbon suboxide (C3O2).

Carbon monoxide (CO)

• Carbon monoxide (CO) is one of the most serious air pollutants. It is a colourless and odourless gas.

• The natural concentration of CO in air is around 0.2 ppm. Natural sources of CO include volcanoes and bushfires. Other sources are incomplete combustion of carbon, automobile exhaust. incomplete combustion of coal, firewood, petrol, etc.

• Effects of CO to human beings: It binds to haemoglobin to form carboxyhaemoglobin, which is about 300 times more stable than the oxygen-haemoglobin complex. In blood, when the concentration of carboxyhaemoglobin reaches about 3–4 per cent, the oxygen carrying capacity of blood is greatly reduced.

• This oxygen deficiency, results into headache, weak eyesight, nervousness and cardiovascular disorder. In female smokers, increased CO level in blood may induce premature birth, spontaneous abortions and deformed babies.

Carbon dioxide (CO2)

• CO2 is a colorless and odorless gas vital to life on Earth. Exists in atmosphere as a trace gas at a concentration of about 380 ppm (0.038%) by volume.

• Sources: Burning of fossil fuels such as coal, oil, and natural gas for energy, It is also emitted during volcanic eruptions.

• Increased use of fossil fuels, a large amount of CO2 gets released into the atmosphere. Excess of CO2 in the air is removed by green plants by photosynthesis.

• Deforestation and burning of fossil fuel increases the CO2 level and disturb the balance in the atmosphere. The increased amount of CO2 in the air is mainly responsible for global warming.

Global Warming and Greenhouse Effect

The average Earth surface temperature is 14° C. or 57.2° F

• Global Warming is the steady increase of Earth's average surface temperature due to effect of greenhouse gases (CO2,CH4,N2O and CFC etc.,)

• Global Warming: About 75 % of the solar energy reaching the earth is absorbed by the earth’s surface, which increases its temperature. The rest of the heat radiates back to the atmosphere. Some of the heat is trapped by gases such as CO2, CH4, O3, CFCs and water vapour in the atmosphere. Thus, add to the heating of the atmosphere. This causes global warming.

• Greenhouse effect: Ozone Maintains the temperature and makes the earth perfect for life. CO2 trapped for photosynthesis. If the amount of CO2 crosses the ambient level of 0.03%, the natural greenhouse balance may get disturbed and contribute to global warming.

Sunlight's composition (Ground level/ per Sq/m) :o Infrared radiation: 527 (W) oVisible light: 445 (W)oUltraviolet radiation: 32 (W)

Atmospheric Methane (CH4)

• Atmospheric CH4 concentrations is one of the most potential greenhouse gas  in atmosphere. it traps 29 times more heat than CO2. The concentration of CH4 in atmosphere is 1800 ppb.

• Sources: Methane emissions results from livestock, agricultural practices, decay of organic waste in municipal solid waste landfills and microbial degradation of organic matter.

• The waterlogged soil of rice paddies provides ideal conditions for methanogenesis, and produced methane oxidized by methanotrophs is the major source for atmospheric CH4.

Nitrous Oxide: (Laughing Gas)• Nitrous oxide occurs naturally in the environment. The

atmospheric concentration of N2O is around 320ppb.• In recent years, their quantities have increased significantly

due to the use of chemical fertilizers and the burning of fossil fuels.

• If these trends continue, the average global temperature will increase to a level which may lead to melting of polar ice caps and flooding of low lying areas all over the earth.

Chlorofluorocarbon (CFC): •CFC are man-made industrial organic chemical compound that contains only carbon, chlorine, and fluorine. •The most common representative is dichlorodifluoromethane (R-12 or Freon-12). •Many CFCs have been widely used as refrigerants, propellants (in aerosol applications), and solvents. Because CFCs contribute to ozone depletion in the upper atmosphere.

Acid Rain

• Acid rain, or acid deposition, is a broad term that includes any form of precipitation with acidic components, such as sulfuric or nitric acid that fall to the ground from the atmosphere in wet or dry forms. This can include rain, snow, fog, hail or even dust that is acidic.

• Acid rain is a precipitation with unusually acidic due to possesses elevated levels of hydrogen ions (low pH). Normally rain water has a pH of 5.6 due to the presence of H+ ions formed by the reaction of rain water with CO2 together to form carbonic acid.

H2O (l) + CO2 (g) ⇌ H2CO3 (aq)

Carbonic acid then can ionize in water forming low concentrations of hydronium and bicarbonate ions:

H2O (l) + H2CO3 (aq) ⇌ HCO3− (aq) + H3O+ (aq)

What Causes Acid Rain?

• Acid rain results when sulfur dioxide (SO2) and nitrogen oxides (NOX) are emitted into the atmosphere and transported by wind and air currents.

• The SO2 and NOX oxidation reaction with water, oxygen and other chemicals to form sulfuric and nitric acids. These then mix with water and other materials before falling to the ground.

Sources:

• Natural sources such as volcanoes eruption.• Burning of fossil fuels to generate electricity. Two thirds of SO2 and one

fourth of NOX in the atmosphere come from electric power generators. Vehicles and heavy equipment, oil refineries and other industries.

2SO2 (g) + O2 (g) + 2H2O (l) → 2H2SO4 (aq)

4NO2 (g) + O2 (g)+ 2H2O (l) → 4HNO3 (aq)

Particulate Pollutants

Taj Mahal was affected due to serious levels of sulphur and nitrogen oxides. It is because of large number of power plants and industries set up around this area. Acid rain reacted with the marble (Calcium Carbonate -CaCo3) of Taj Mahal and damage the Marble structure.

•Bhopal gas disaster was occurred on 2–3 December 1984 at the Union Carbide India Limited (UCIL) pesticide plant in Bhopal, Madhya Pradesh.

•Over 500,000 people were exposed to Methyl Isocyanate (MIC) gas and other chemicals emitted from industry.

Effect of Acid Rain in Taj Mahal:-

Bhopal Gas tragedy

Particulate Pollutants

oParticle pollution or Particulate matter (PM), is a complex mixture of extremely small particles and liquid droplets that get into the air. 

oThese are outcome of vehicle emissions, smoke particles from fires, dust particles and ash from industries.

oParticulates in the atmosphere may be viable or non-viable.oThe viable particulates e.g., bacteria, fungi, moulds, algae etc.,

are minute living organisms.oOnce inhaled, these particles can affect the Heart and Lungs and

cause serious health effects. Human beings are allergic to some of the fungi found in air. They can also cause plant diseases

oNon-viable particulates may be classified according to their nature and size such as Smoke particulates, Dust, Mists, Fumes

Non-viable particulates• Smoke particulates: solid or mixture of solid and liquid particles

formed during combustion of organic matter. Ex:-cigarette, smoke from burning of fossil fuel and garbage.

• Dust: Fine solid particles over 1μm in diameter produced during crushing solid materials, saw dust, pulverized coal, cement and fly ash.

• Mists: Particles of spray liquids and by condensation of vapours in air. Ex:- Sulphuric acid mist and Pesticides.

• Fumes: Condensation of vapours during sublimation, distillation, boiling solvents and metallic oxides.

Effect of particulate pollutants:

• Particulate pollutants bigger than 5 μm lodge in the nasal passage, whereas particles of about 10 μm enter into lungs easily.

• Lead used to be a major air pollutant emitted by vehicles. Lead interferes with the development and maturation of red blood cells.

Particle pollution includes:

• PM10 : Inhalable particles, with diameters that are generally 10 micrometers and smaller.

• PM2.5 : Fine inhalable particles, with diameters that are generally 2.5 micrometers and smaller.

Smog

• Kind of air pollution originally named for the mixture of smoke and fog in the air. There are two types of smog…

• Classical smog: occurs in cool humid climate. It is a mixture of smoke, fog and sulphur dioxide (SO2).

• Photochemical smog: Photochemical smog is a mixture of pollutants that are formed when nitrogen oxides and volatile organic compounds (VOCs) react to sunlight, creating a brown haze occurs in warm, dry and sunny climate. It produced by automobiles and factories.

Formation of photochemical smog• When fossil fuels are burnt, a variety of pollutants are emitted into

the earth’s troposphere.• Sources: In nature bushfires, lightning and the microbial

processes are natural sources and combustion incomplete of fossil fuels are anthropogenic sources of formation smog.

How is smog formed? NO is converted into nitrogen dioxide (NO2). This NO2 in turn absorbs energy from sunlight and breaks up into nitric oxide and free oxygen atom.

Oxygen atoms are very reactive and combine with the O2 in air to produce O3

The O3 reacts rapidly with the NO(g) formed in the reaction (i) to regenerate NO2

contribute to haze.

O3 is a toxic gas and both NO2 and O3 react with the un burnt hydrocarbons in the polluted air to produce chemicals such as formaldehyde, acrolein and peroxyacetyl nitrate (PAN).

Effects of photochemical smog

How can photochemical smog be controlled ?

• Control the emission of primary precursors NO2,O3 and hydrocarbons

• Use of catalytic converters in automobiles reduce prevents the release of nitrogen oxide and hydrocarbons to the atmosphere.

Stratospheric Pollution

Stratosphere is the layer just above troposphere. The upper stratosphere consists of considerable amount of ozone (O3), which protects us from the harmful ultraviolet (UV) radiations coming from the sun. These radiations cause skin cancer in humans. Therefore, it is important to maintain.

Formation and Breakdown of OzoneIn stratosphere, the O2 is partially converted into O3. It is a two step process.

Step 1: The UV radiation coming from the sun has sufficient energy to split the O2 into 2 oxygen radicals.

O2 + UV 2O

Step 2: The oxygen radicals react with more oxygen molecules to form ozone.

O3 thermodynamically unstable and decomposes to molecular O2

Thus dynamic equilibrium exists.

 O3 + UV   O2 + ODepletion of ozone layer in stratosphere

In recent years, due to human activity two compounds NO and CFC, are responsible for depletion of ozone layer.

Nitric Oxide

The NO reacts with O3 causing decrease the amount of O3 and forms NO2 which reacts with oxygen radicals for regeneration of  NO, while amount of O3 decreases. NO + O3  NO2 + O2

NO2 + O NO + O2

Chlofofluoro carbons (CFC) or freons

CFC used in refrigerators, air conditioners as propellants and by the electronic industry for cleaning computer parts etc. Once CFCs are released in the atmosphere, they mix with the normal atmospheric gases.

In stratosphere, they get broken down by powerful UV radiations, releasing chlorine free radical.

The chlorine radicals are continuously regenerated and cause the breakdown and damaging of ozone layer.One molecule of CFC can destroy more than one thousand O3 molecules in stratosphere.

Hypochlorite

Californium dichloride

Effects of Depletion of the Ozone Layer

• Due to depletion of O3 layer, more U.V. radiations fall on the earth surface.

• UV radiations lead to ageing of skin, cataract, sunburn, skin cancer, killing of many phytoplankton, damage to fish productivity etc.

• The UV radiations affect plants proteins and thus reduce the chlorophyll.

• UV radiations also tend to damage the immune system.

• Increases evaporation of surface water through the stomata of the leaves and decreases the moisture content of the soil.

WATER POLLUTION

• Water is essential for life. Without water there would be no life.

• Water pollution is the process of contamination of water of natural or artificial water resources with harmful substances.

• Pollution of water mainly originates from Human activities.

• Sources of Water Pollution:

Point Source: Easily identified place or source of pollution. Ex;- Municipal wastes and industrial discharge.Non point sources:- Pollution are those where a source of pollution cannot be easily identified, e.g., agricultural run off (from farm, animals and crop-lands), acid rain, storm-water drainage.

Major Water Pollutants

Causes of Water Pollution

Pathogens: Disease causing agents includes bacteria, virus and other organisms that enter water from domestic sewage and animal excreta. Ex;- Amoebiasis, Botulism, Cholera, E. coli Typhoid, Hepatitis A etc.,

Organic wastes: organic matter such as leaves, grass, trash etc. as a consequence of run off. Excessive phytoplankton growth. These are biodegradable.

Biochemical Oxygen Demand (BOD)

• The polluted water contain  large amount of inorganic and organic compounds. Some of these can be oxidised by microorganisms.

• Organic matter is added to water, all the available oxygen is used up. This causes oxygen dependent aquatic life. Anaerobic bacteria begin to break down the organic waste and produce chemicals that have a foul smell and are harmful to human health.

• Bacteria degrade these organic wastes and keep the water depleted in dissolved oxygen.

• Biochemical Oxygen Demand (BOD): Amount of dissolved oxygen needed by aerobic biological organisms to break down organic material present in a given water sample at certain temperature over a specific time period.

• The BOD is taken as a realistic measure of water quality – clean water would have a BOD value of less than 5 ppm whereas highly polluted river water could have a BOD value of 17 ppm or more.

• Chemical Oxygen Demand (COD) is the amount of oxygen required to oxidise and stabilize the organic and inorganic matter present in a certain volume of water.

Chemical Pollutants• Heavy Metals: Cd, Pb & Hg are known as heavy metals. These may be

present in industrial  or mining waste. They are highly toxic and cause damage to kidney, liver, brain and central nervous system.

• Detergents & Fertilizers: These may contain phosphate. The addition of phosphorus to water, encourages the formation of algae, which reduces the DO concentration of water. The process is known as eutrophication.

• Acid- polluted water (pH < 3) : This is deadly to most forms of aquatic life. Industrial wastes and acid rain contribute to the acidity of natural water.

International Standards for Drinking WaterFluoride: Soluble fluoride is added to drinking water limits to a concentration of 1 ppm. High concentrations are poisonous and are harmful to bone and teeth at levels over 10 ppm.Lead: Drinking water gets contaminated with Pb when lead pipes are used for transportation of water. The limit for the concentration for lead ions in drinking water is 50 ppb.pH:  The pH of drinking water should be between 5.5 and 7.5. A decrease in the pH of the water increases the solubility of metal ions.

SOIL POLLUTION

• Soil pollution is caused by Chemicals such as pesticides , insecticides, herbicides and fungicides are used for protection of food crops from damage.

• Chemical fertilizers are used for improving crop yield. • Apart from this, polybags and other type of polymers are used for

packaging and storage of food items. Most of the things are non-biodegradable

Pesticides: • They synthetic toxic chemicals and are used to stop the

reproduction and growth of unwanted organisms. • Synthetic pesticides has possible effect upon human health. For

example DDT, Aldrin and Dieldrin.• They transferred from lower trophic level to higher trophic level

through food chain• They causes serious metabolic and physiological disorders.

Herbicides:• Herbicides are used to kill weeds.

Sodium chlorates, NaClO3 and sodium arsenite Na3AsO3 were commonly used as weed killers.

• Organic herbicides now used. They are much more toxic to certain type of plants than to others.

• Organic herbicides such as trizines are presently widely used to kill weeds in cornfields.

Fungicides: • Fungicides are the pesticides used to check the growth of fungi.• Fungi, are plants without chlorophyll, they cannot use solar

energy for preparing their food. They live as saprophytes.• Organic compounds of mercury have been used as fungicides and

this has detrimental effect

INDUSTRIAL WASTESo Industrial wastes are contribute to

major sources of Environmental pollution.

oChemical and other wastes polluting the air, water, and land and causing pollution and climate change which is dangerous for earth’s biodiversity.

o Industries discharges biodegradable and non-degradable wastes. Biodegradable wastes are generated by cotton mills, food processing units, paper mills, Pharmaceuticals and textile factories.

oNon-biodegradable wastes are generated by power plants, steel plants, metallic industries, Fertilizer industries etc.,

Strategies to control Environmental Pollution• Pollution prevention methodology to reduces the amount of pollution

generated by industry, agriculture or consumers.

Waste Management

• It is the activities and actions required to manage waste from its inception to its final disposal like collection, transport, segregation, treatment and disposal.

• It includes Municipal, agricultural, and hazardous wastes.

• Waste management is intended to reduce adverse effects of waste on health and environment.

Collection and Disposal

• Domestic wastes are collected carried to the disposable site sorted out and separated. Non-biodegradable materials are sent for recycling. Biodegradable wastes are deposited in land fills and are converted into compost.

Disposal solutions

Landfill: Dumping and burial of solid wastes. It categorized into…..•Municipal solid waste (MSW) landfills - uses a synthetic (plastic) liner to isolate the trash from the environment•Construction and demolition waste landfills - consist of the debris generated during the construction, renovation, and demolition of buildings, roads, and bridges.•Industrial Waste Landfills- nonhazardous solid waste, consists of nonhazardous waste associated with manufacturing and other industrial activities.

Incineration: Incineration is a disposal method of solid organic wastes subjected to combustion so as to convert them into residue and gaseous products. Incinerators convert waste materials into heat, gas, steam, and ash. Ex;- Hazardous waste materials.

Recycling: It’s method of collection and reuse of waste materials such as consumer products include aluminium, copper wire, steel from food, rubber tyres, polyethylene materials, paperboard cartons, newspapers, magazines and light paper.

Re-use: Recoverable materials that are organic in nature, such as dead biological materials, Energy recovery from wastes including Pyrolysis, into usable heat, electricity, or fuel and chemical refinery.

GREEN CHEMISTRY or SUSTAINABLE CHEMISTRY

• Green chemistry is the design of utilising the existing knowledge and principles of chemistry and other sciences to reduce the adverse impact on environment.

• Green chemistry is a production process that would bring about minimum pollution or deterioration to the environment.

The principles cover such concepts as:• The design of processes to maximize the amount of raw material

that ends up in the product.

• The use of renewable energy sources• The use of safe, environmentally benign substances, including

solvents, whenever possible.

• The design of energy efficient processes• Avoiding the production of waste, which is viewed as the ideal form

of waste management.