UNIT-VII SOLID AND HAZARDOUS WASTE MANAGEMENT

Any material that is thrown away or discarded as useless and unwanted is considered
as solid waste. At first glance, the disposal of solid waste may appear to be a very simple and
mundane problem. In this age of lasers, microcomputers, and space flight, it hardly seems
possible that garbage disposal should present any great challenge. But many factors make
solid waste disposal a complex problem of huge proportions for a modern industrial society.

Classification of solid wastes

Domestic and municipal wastes: These include garbage and rubbish, like waste paper,
plastic, cloth from households, office, hostel and market.
Industrial wastes: The two general categories are process and non-process wastes. The
non-process wastes are common to all industries such as packaging, office and cafeteria
wastes. Process wastes are more complex and specific to the industrial plants. Their
composition depends on type of products produced.
Agricultural wastes: These include cereal and millet straw, paddy husk, sugarcane trash and
other crop residues.
Special wastes: The waste materials which endanger public health and welfare and seriously
affect environment are: a) Radioactive wastes from atomic power stations, labs and hospitals
b) Toxic wastes such as pesticides, heavy metals, pharmaceuticals c) Biological products
such as antibiotics, enzymes, pathogens.
Properties of waste
Composition: The composition of solid waste varies with several factors such as degree of
urbanization and industrialization, per capita income, social customs, climatic conditions of
the area, Acceptability of packaged foods, Frequency of collection by the municipality, etc.
Density: The Density of solid waste varies from 150 kg/m3 to 800 kg/m3 depending upon the
waste composition and degree of compaction
Energy content: Municipal solid waste generally contains about 50% of combustible matter.
The average calorific value of the solid waste is found to be 900- 1800 KCals/kg.
Moisture content: The moisture content of solid wastes is the amount of combined and free
moisture present which is expressed as the mass of moisture per unit mass of wet or dry
material.
Muncipal Solid Waste (MSW)
The term municipal solid waste (MSW) is generally used to describe most of the non-
hazardous solid waste from a city, town or village that requires routine collection and
transport to a processing or disposal site. Sources of MSW include private homes,
commercial establishments and institutions, as well as industrial facilities. However, MSW
does not include wastes from industrial processes, construction and demolition debris,
sewage sludge, mining waste or agricultural wastes. MSW is also called as trash or garbage.
In general, domestic waste and MSW are used as synonyms. Municipal solid waste contains a
wide variety of materials. It can contain food waste (like vegetable and meat material,
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leftover food, eggshells etc.), which is classified as wet garbage as well as paper, plastic,
tetrapack, plastic cans, newspaper, glass bottles, carboard boxes, aluminum foil, metal items,
wood pieces, etc., which is classified as dry garbage. The different types of domestic wastes
generated and the time taken for them to degenerate is illustrated in the table given below.
Domestic wastes and their degeneration time
Organic kitchen waste vegetables, fruits - 1-2 weeks
Paper, cardboard paper - 15 days-1 month
Cotton clothes - 2-5 months
Woolen clothes about - one year
Metal cans, tin, aluminum - 100-500 years
Plastics - 1 million years

India’s urban population slated to increase from the current 330 million to about 600
million by 2030, the challenge of managing municipal solid waste (MSW) in an
environmentally and economically sustainable manner is bound to assume gigantic
proportions. The country has over 5,000 cities and towns, which generate about 40 million
tonnes of MSW per year today. Going by estimates of The Energy Research Institute (TERI),
this could well touch 260 million tonnes per year by 2047.
The functional elements of MSW management
The municipal solid waste industry has four components: recycling, composting,
landfilling, and waste-to-energy via incineration. The primary steps are generation,
collection, sorting and separation, transfer and disposal/utilisation.
Waste generation encompasses activities in which materials are identified as no
longer being of value and are either thrown out or gathered together for disposal. The
functional element of Collection includes not only the gathering of solid waste and recyclable
materials, but also the transport of these materials, after collection, to the location where the
collection vehicle is emptied. This location may be a materials processing facility, a transfer
station or a landfill disposal site.
Waste handling and separation involves activities associated with waste
management until the waste is placed in storage containers for collection. Handling also
encompasses the movement of loaded containers to the point of collection. Separating
different types of waste components is an important step in the handling and storage of solid
waste at the source. The types of means and facilities that are now used for the recovery of
waste materials that have been separated at the source include curbside collection, drop off
and buy back centers.
 Collection of segregated municipal waste is an essential step in MSWM. Inefficient
waste collection services have an impact on public health and aesthetics of towns and
cities.
 Collection of wet, dry and domestic hazardous waste separately ensures maximum
recovery of recyclables. It also enhances the potential of cost-effective treatment of such
wastes. eg. production of compost from pure organic waste.
 Waste collection services are divided into
 Primary Collection
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  Secondary collection.
 Primary collection refers to the process of collecting, lifting and removal of segregated
solid waste from source of its generation including households, shops, offices, markets,
hotels, institutions and other residential or non-residential premises and taking the waste
to a storage depot or transfer station or directly to the disposal site, depending on the
size of the city and the waste management system prevalent in the city.
 Primary collection must ensure separate collection of certain waste streams depending
on the separation and reuse system applied by the respective town or city .
 Secondary collection includes picking up waste from community bins, waste storage
depots, or transfer stations and transporting it to waste processing sites or to the final
disposal site.
 At the secondary collection points, segregated waste must be stored on-site in separate
covered bins for further collection and should be kept separate during all steps of waste
collection, transportation, and processing. ULBs should ensure that at the secondary
storage points the waste is should be attended daily or before container starts
overflowing.
 A well synchronized primary and secondary collection and transportation system, with
regular and well communicated intervals of operation (primary collection), is essential
to avoid containers’ overflow and waste littering.
 The vehicles used for transportation should be covered.
 Vehicles should have a facility to prevent spillage of waste and leachate en-route to the
processing or disposal facility.
 It is essential to separate street sweeping waste and silt cleaned from drains completely
from household waste streams through all stages of collection, transport, and treatment,
since street sweeping and drain silt can be infiltrated with significant amounts of toxic
substances (e.g., heavy metals) and are often responsible for contamination.

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Transfer and transport involves two main steps.
First, the waste is transferred from a smaller collection vehicle to larger transport
equipment. The waste is then transported, usually over long distances, to a processing or
disposal site. Today the disposal of wastes by land filling or land spreading is the ultimate
fate of all solid wastes, whether they are residential wastes collected and transported directly
to a landfill site, residual materials from materials recovery facilities (MRFs), residue from
the combustion of solid waste, compost or other substances from various solid waste
processing facilities. A modern sanitary landfill is not a dump; it is an engineered facility
used for disposing of solid wastes on land without creating nuisances or hazards to public
health or safety, such as the breeding of insects and the contamination of ground water.
Municipal solid waste can be used to generate energy.
Hauled and Stationary containers
The design of an efficient waste collection system requires careful consideration of the
type, size and location of containers at the point of generation for storage of wastes until they
are collected. While single-family households generally use small containers, residential
units, commercial units, institutions and industries require large containers. Smaller
containers are usually handled manually whereas the larger, heavier ones require mechanical
handling. The containers may fall under either of the following two categories:
 Stationary containers: These are used for contents to be transferred to collection
vehicles at the site of storage.
 Hauled containers: These are used for contents to be directly transferred to a
processing plant, transfer station or disposal site for emptying before being returned to
the storage site.

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 Several technologies have been developed that make the processing of MSW for
energy generation cleaner and more economical than ever before, including landfill gas
capture, combustion, pyrolysis, gasification, and plasma arc gasification. While older waste
incineration plants emitted high levels of pollutants, recent regulatory changes and new
technologies have significantly reduced this concern.
Waste stream assessment (WSA)
Waste stream assessment (WSA) is a method to determine the basic aspects of
quantity, composition, and source of wastes that are essential for making decisions about the
SWM system, finance, and regulations.
Heating value
The heating value (KJ/Kg) of waste materials is determined experimentally using the
Bomb calorimeter test. This test evaluates the potential of waste materials to be used as fuel
for incineration.
Component Typical heating value (KJ/Kg)
Food wastes 4500
Paper 16500
Cardboard 16000
Plastics 32500
Rubber 18500
Wood 18500
Glass 140
Auxiliary operations necessary for solid waste treatment
1. Transport and handling
2. Pulverization
3. Compaction
1. Transport and handling
Solid wastes are collected from source, transported in trucks with hydraulic and
pneumatic system to a central place and to compact the waste to a high density, for disposal.
2. Pulverization
Pulverization of solid wastes is carried out prior to loading, land filling, compacting
or incineration to facilitate these processes. Taw roll, impact and gyratory crushers and
hammer mills are used for pulverization. It makes the solid waste homogenous and helps in
greater initial settlement. The land can be more easily reclaimed and built on.
3. Compaction
Compaction and balling of solid wastes using hydraulic or pneumatic processes lead
to reduction in refuse volume, reduction in collection and transport time and cost, lesser
storage area and safety hazards and cleaner storage area.
The most effective way to ameliorate the solid waste disposal problem is to reduce the
generation and toxicity of waste. But, as people search for better life and higher standard of
living they tend to consume more goods and generate more wastes. Consequently society is
searching for improved methods of waste management and ways to reduce the amount of
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waste management system. This consists of reducing the amount of toxicity of the wastes at
the source, recycling, reusing or composting as much of the waste as is economically
reasonable. Burning the waste that cannot be economically recycled to generate heat reduces
the need for fossils and nuclear fuels.
Recycling and waste reduction play an important part in any waste management
strategy. But engineering analysis clearly shows that these options alone cannot solve the
solid waste problem. At the same time, according to best estimates, it may be possible to
reach recycling technologies that must be developed, additional markets must be found, and
industry must produce more products that are easy to recycle. All the same, even if all of
these steps are successfully taken more than 160 million tons of solid waste still have to be
treated by other means, such as waste – to – energy combustion and land filling.
Technologies in solid waste management
Solid waste management is a difficult process because it involves many disciplines.
These include, technologies associated with the control of generation, storage, collection,
transfer and transportation, processing, marketing, incineration and disposal of solid wastes.
All of these processes have to be carried out within existing legal and social guidelines that
protect the public health and environment and are aesthetically acceptable. They must be
responsive to public attitudes and the disciplines included in the disposal process include
administrative, financial, legal, architectural, planning and engineering functions. For
successful integrated solid waste management plant, it is necessary that all these disciplines
communicate and interact with each other in a positive interdisciplinary relationship .The
various techniques employed in solid waste management include,
1. Composting
2. Sanitary land filling (Controlled tipping)
3. Thermal process (Incineration and pyrolysis)
4. Recycling and reuse
Composting
It is being increasingly realized that composting is an environment friendly process to
convert wide variety of wastes into valuable agricultural inputs. This process minimizes the
environmental problems. Composts are excellent source of humus and plant nutrients, the
application of which improves soil biophysical properties and organic matter status of the
soil. Composting can be defined as the biological conversion of organic wastes into an
amorphous dark brown to black colloidal humus like substance under conditions of optimum
temperature, moisture and aeration. Nutrient content of compost depends largely on the
nutrient content of the wastes. Composting is a process in which the organic portion of solid
waste is allowed to decompose under carefully controlled conditions. It is a biological rather
than a chemical or mechanical process; decomposition and transformation of the waste
material are accomplished by the action of bacteria, fungi, and other microorganisms.
With proper control of moisture, temperature, and aeration, a composting plant can
reduce the volume of raw organic material by as much as 50 per cent. In addition,
composting can stabilize the waste and produce an end product that may be recycled for

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beneficial use. The end product is called compost or humus. It resembles potting soil in
texture and earthy odor, and it may be used as a soil conditioner or mulch.
A complete municipal solid waste (MSW) composting operation includes sorting and
separating, shredding and pulverizing, digestion, product upgrading, and finally marketing.
Sorting and separation operations are required to isolate organic, decomposable waste
materials from the plastic, glass, metal, and other non-biodegradable substances. Solid waste
sorting and separation methods are a key part of MSW recycling operations.
Shredding and pulverizing serve to reduce the size of the individual pieces of the
organic waste, resulting in a relatively uniform mass of material. This facilitates handling,
moisture control, and aeration of the decomposing waste. Size reduction also helps optimize
bacterial activity and increases the rate of decomposition. After size reduction, the wastes are
ready for the actual composting or digestion step. Digestion may take place in open windrow
or in an enclosed mechanical facility.
A windrow is a long, low pile of the prepared organic waste, usually about 3m (10 ft)
wide at the base and about 2 m (6 ft) high. Most windrows are conical in cross section and
about 50 m (150 ft) in length. The composting waste is aerated by periodically turning each
windrow. Turning frequency varies with moisture content and other factors. When moisture
content is maintained at about 50 per cent, windrows are turned two or three times a week
and in some cases daily.
Generally, open – field windrow composting takes about 5 weeks for digestion or
stabilization of the waste material. An additional 3 weeks may sometimes be required to
ensure complete stabilization. Temperatures in an aerobic compost windrow may reach 65
oC (150 oF) because of the natural metabolic action of thermophilic microbes that thrive
at such elevated temperatures. The relatively high temperatures destroy most of the
pathogenic or disease-causing organisms that may be present in the waste.
Open-field windrow composting requires relatively large land areas. To reduce land
requirements, various types of enclosed mechanical systems can be used in lieu of the open-
field method. A variety of mechanical type compost systems are available. Oxygen is
supplied to the waste material by forced aeration, stirring, or tumbling.
In addition to reducing land requirements, enclosed mechanical compost facilities can
reduce the time required for stabilization from about 5 weeks to about 1 week.
Composting is the aerobic, thermophilic degradation of organic matter present in the
refuse by microbes, predominantly by fungi and actinomycetes, which are favoured by semi
moist condition that prevail in the process. The control parameters for optimum composting
include, temperature (40 oC), moisture (40.7%), pH (4.5 – 9.5), nutrients (C:N ratio 40:1);
C:P ratio (100:1), air (0.5 – 0.8 m / d / kg volatile solid) and particle size (6-25 mm).
The digestion of the waste is carried out naturally in an outside decomposition area in
windrows (for five weeks) or in mechanized composting plants (for 4 to 6 days). In natural
system, the garbage is mixed with nutrient source (sewage sludge / animal manure) and a
filler (wood chips) to provide entry of air. The mixture is turned over twice a week and the

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process is completed in 4-6 weeks. The darkening of refuse, fall in temperature and a musty
odour indicate completion of the process.
Before the stabilized compost or humus can be sold for use as a mulch or soil
conditioner, it must be processed further to upgrade or improve its quality and appearance.
This includes drying, screening, and granulating or pelletizing. Sometimes, the compost is
placed in bags, although bulk sale is more efficient and economical.
Compost can increase the organic and nutrient content of soil and improve its texture
and ability to retain moisture.
Co-Composting
An interesting example of integrated waste management is co-composting of
municipal solid waste and sewage sludge. Sewage sludge adds nitrogen, phosphorous, and
other elements that enrich the solid waste and help the composting process. The sludge is
first dewatered so that it does not add too much moisture to the compost pile. The dewatered
sludge and organic portion of MSW must be thoroughly mixed. At a time when ocean
disposal of sludge has been banned and sludge incinerators meet with much public
opposition, co-composting may offer an increasingly viable technique for processing both
sludge and MSW organics prior to final disposal.
Vermicomposting
The key role of earthworms in improving the soil fertility is well known for a longer
period. Earthworms feed on any organic wastes, consume three to five times their body
weight and after using 5 to 10 per cent of the organic wastes for their growth, excrete the
mucus coated undigested matter as worm casts. Worm casts consist of organic matter that
has undergone physical and chemical breakdown through the activity of the muscular
gizzard, that grinds the material to a particle size of 1-2 micron. The nutrients present in the
worm casts are readily soluble in water for the uptake of plants. Vermicastings are rich
sources of macro and micronutrients, vitamins, enzymes, antibiotics, growth hormones and
immobilized micro flora.
Vermicompost refers to organic manure produced by earthworms. It is a mixture of
worm castings, including humus, live earthworms, their cocoons and other microorganisms.
Vermicomposting is an appropriate method for disposal of non-toxic solid and liquid organic
wastes. It helps in cost effective and efficient recycling of animal wastes (Poultry droppings,
horse, piggery excreta and cattle dung), agricultural residues and industrial wastes using low
energy.

Types of earthworms

Several types of earthworms are found in our soils. Earthworms can be divided into
the following two categories:
1. Epigeic – the surface living worms
2. Endogeic – the burrowing worms

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Epigeic: These worms are found on the surface and are reddish brown in colour. They do
not process the soil but are efficient in composting of organic wastes. They enhance the rate
of organic manure production through biodegradation or mineralization. Eg. Lampito
mauritii, Octochaetona serrata, Perionyx excavatus

Endogeic: These species burrow and mix the soil, from different horizons in the profile.
They ingest organic and mineral fraction of soil, thus promoting the formation of organo
mineral complexes. Organo – mineral crumbs are brought from deeper parts of the soil
profile to the surface. Different species of earthworms show specificity to soil types,
moisture content and temperature. Species such as Lampito mauritii, Octochaetona serrata,
Lumbricus terrestris, Pontosolex carethrurus and Octochaetona thurstoni are examples for
endogeic earthworms.

Subsoil dwellers: Subsoil- dwellers or anecic species live in permanent vertical burrows that
can be 5 or 6 feet deep. Their burrows are capped by crop residue that they pull to the
entrance. The nightcrawler (Lumbricus terrestris) is the most prominent member of the
group.

Method of vermicomposting

 Selection of earthworm: Earthworm that is native to the local soil may be used
 Size of pit: Any convenient dimension such as 2m x 1m x 1m may be prepared
 Preparation of vermibed: A layer, 15-20 cm thick of good loamy soil above a thin
layer of (5 cms) broken bricks and sand should be made.
 Inoculation of earthworms: About one hundred earthworms are introduced as an
optimum inoculating density into a compost pit of about 2m x 1m x 1m, provided with
vermibed
 Organic layering: It is done on the vermibed with fresh cattle dung. The compost pit
is then layered to about 5 cm with dry leaves or hay or organic wastes. Moisture
content of the pit is maintained by the addition of water.
 Wet organic layering: It is done after four weeks with moist green organic waste,
which can be spread over it to a thickness of 5 cm. This practice can be repeated every
4 days. Mixing of wastes periodically without disturbing the vermibed ensures proper
vermicomposting. Wet layering with organic wastes can be repeated till the compost
pit is nearly full.
Harvesting of compost: At maturation (after 120 days), the moisture content is brought
down, by stopping the addition of water. This ensures drying of compost and migration of
worms in to the vermibed. The mature compost, a fine loose granular mass
(about 1500 kg), is removed from the pit, sieved, dried and packed.
Nutrient status of vermicompost prepared by Perionyx excavatus

Macronutrients
Total nitrogen % 0.66
Total P2O5% 1.93
Total K2O% 0.42

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 Micro nutrients
Fe (ppm) 19.8
Zn (ppm) 0.90
Mn (ppm) 16.50
Cu (ppm) 2.30
General characters of vermicompost
pH 7.00
EC dsm-1 1.20
Organic carbon% 30.50

Sanitary land filling (Controlled tripping)

Land filling is the most common and economic method of solid waste disposal. The
indiscriminate land filling of solid waste in open dumps without adequate control and
consideration of sanitation and public health as generally followed in India is dangerous. It
results in water pollution, bad odour, fire and breeding of flies and rats.
It should be replaced by sanitary land filling or controlled tipping. The construction
of sanitary land filling includes:
1) Deposition of solid waste in such a way to have a working force of minimum area.
2) Spreading and compaction of waste in thin layers
3) Covering of the waste with a layer of compacted cover soil daily.
4) Final cover of the entire construction with compacted earth layer of 1.0 m thick.
The solid wastes in sanitary land fill are degraded by soil microbes. In comparison with
other biological treatment systems such as activated sludge and anaerobic digestion, the
microbial degradation of solid waste proceeds at a slow rate.
Thermal process
Incineration
Incineration is a process of destruction of waste at high temperature. The combustible
wastes are converted through controlled combustion to a residue, which contain no
combustible matter. If land suitable for solid waste (SW) land filling operations is not
available within economic haul distances, then incineration is necessary. The solid waste is
reduced in volume (80% - 90%) and height (98-99%).
Incinerator can accept toxic and industrial wastes of any size in solid or powdery
form. The other special wastes include hospital wastes, putrifiable organic solids from
slaughter houses.
Pyrolysis (Destructive distillation)
Pyrolysis is the process of conversion of biomass into solid, liquid and gaseous
energy. Pyrolysis results in the chemical breakdown of organic carbon material into three
basic components:

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 1) Gas phase containing mainly hydrogen, CO2, CO and CH4.
2) Tar or oil phase containing simple organic acids, methanol and acetone.
3) Char phase made up of pure carbon and inert material.

Pyrolysis does not cause pollution of the atmosphere and large quantities of potentially
hazardous plastics could be treated. There is no single prescription for an integrated waste
management program that successfully works in every instance. Each situation must be
analyzed on its own merit, an appropriate integrated waste management plan must be
developed from hard data, and social attitudes and the legal frame work must be taken into
account. The waste management disposal field is in a constant state of flux and appropriate
solutions should be innovative, as well as technically and economically sound.
Sludge management
Suspended solids removed from wastewater during sedimentation and then
concentrated for further treatment and disposal are called sludge or biosolids. Even in fully
aerobic waste treatment processes in which sludge is repeatedly recycled, most of the sludge
must eventually be removed from the system.
The task of treating and disposing of this material is called sludge management.
Sludge characteristics
The composition and characteristics of sewage sludge vary widely. Since no two
wastewaters are alike, the sludges produced will differ. Furthermore, sludge characteristics
change considerably with time. Wastewater sludge typically contains organics (proteins,
carbohydrates, fats oils), microbes (bacteria, viruses, protozoa), nutrients (phosphates and
nitrates), and a variety of household and industrial chemicals. The higher the level of heavy
metals and toxic compounds, the greater is the risk to humans and the environment. A key
physical characteristic is the solids concentration, because this defines the volume of sludge
that must be handled.
Sludge is treated prior to ultimate disposal for two basic reasons: volume reduction
and stabilization of organics. Stabilized sludge does not have an offensive odor and can be
handled without causing a nuisance or health hazard. A reduced sludge volume minimizes
pumping and storage requirements and lowers overall sludge-handling costs.
Several processes are available for accomplishing these two basic objectives. They
include sludge thickening, digestion, dewatering, and co-composting. Incineration is
considered as a final disposal option.
Sludge disposal
Widely employed methods for final disposal of waste water sludge have included
ocean dumping, land filling, incineration, land application, and sale as fertilizer.
Gasification
This is the partial combustion of organic materials containing a large amount of
carbon content. At high temperature (roughly 1000°C) they form a gas comprising mainly

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carbon dioxide (CO2), carbon monoxide (CO), nitrogen (N), hydrogen (H), water vapor, and
methane (CH4).
Refuse-derived fuel (RDF)
RDF consists of combustible components of raw waste separated by different
processing steps, such as screening, air classification, ballistic separation, etc. The separated
components can be used as fuel and it has high calorific value than its parent material. Solid
recovered fuel (SRF) is a high-quality alternative to fossil fuel. It is produced from mainly
commercial waste including paper, card, wood, textiles, and plastic. Solid recovered fuel has
gone through additional processing to improve the quality and value. It has a higher calorific
value than RDF and is used in facilities such as cement kilns.

Biomethanation of soil waste

In the case of landfills receiving huge quantities of organic wastes, microbial
degradation is the major process that stabilizes the waste and therefore governs landfill gas
generation and leachate composition. The anaerobic degradation process of wastes undergoes
through the following stages:
1. Hydrolysis and fermentation of solid and dissolved organic components into volatile
fatty acids, alcohols, hydrogen, and carbon dioxide.
2. The products derived from the first stage are then converted into acetic acid, hydrogen
and carbon dioxide by an acidogenic group of bacteria.
3. Methanogenic bacteria convert acetic acid into methane and carbon dioxide.
Hydrogenophilic bacteria convert hydrogen and carbon dioxide into methane.
Non-methane organic compounds (NMOCs) and Landfill gas (LFG) can contaminate
groundwater in unlined landfills and landfills with no or inadequate LFG collection systems.
The contamination takes place through three transfer mechanisms:
1. The direct transfer of NMOCs to groundwater.
2. Condensation of LFG in the vadose zone.
3. Condensation of LFG in vadose zone plus washdown.

The control of escaping LFG by proper extraction ensures its use as a source of
energy. Generally, the landfill gas is extracted during the operation phase by means of gas
wells that are drilled by auger and are driven into the landfill at a spacing of 40 – 70 m. If
landfill gas is not utilized, it should be burnt by means of flaring. As a matter of fact, the
efficient utilization of landfill gas can notably reduce fossil fuel consumption for the
production of electricity and heat.
Leachate Formation
Leachate is a bad odoured liquid comprising soluble components of waste and its
degradation products that are harmful to the environment. The generation of leachate is
caused principally by precipitation percolating through waste deposited in a landfill and is
controlled by a group of factors, such as water availability, landfill surface condition, refuse
state, and condition of surrounding strata. The major toxic substances present in leachate are
ammonia and heavy metals. The water balance equation for landfill requires negative or zero
so that no excess leachate is produced.
Lo = I – E – aW

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Lo = free leachate retained at site (equivalent to leachate production minus leachate leaving
the site); I = total liquid input;
E = evapotranspiration losses;
a = absorption capacity of waste; W = weight of waste disposed.
An appropriate way for controlling the migration of leachate and its toxic constituents
into underlying aquifers or nearby rivers is to use landfill liners to prevent the movement.
Modern landfills generally require a layer of compacted clay with a minimum required
thickness and a maximum allowable hydraulic conductivity, overlaid by a high-density
polyethylene geomembrane. Chipped or waste tires are generally used to support and insulate
the liner.
1. Natural liners
These are generally less permeable, resistant to chemical attack and have good
sorption properties. Commonly used natural liners are compacted clay or shale, bitumen or
soil sealants, etc. They do not act as true containment barriers because leachate may migrate
through them.
2. Synthetic (geo-membrane) liners
Geosynthetic clay liner is usually made of sodium bentonite. It is compacted in
between two thick pieces of geotextile and is able to expand or shrink according to
temperature variations.
3. Composite liners
A composite liner consists of a natural membrane along with a geosynthetic clay liner.
This system is more efficient at reducing leachate migration into the subsoil than either a clay
liner or a single geomembrane layer.
The leachate containing a high concentration of undesirable substances then
undergoes a treatment process for their safe discharge into the environment. The common
treatment processes applied to leachate are:

1. Leachate recirculation
It is defined as the practice of returning leachate to the landfill from which it has been
abstracted. The process reduces the hazardous nature of leachate and helps to wet the waste
thereby increasing the rate of biological degradation. This method of repeatedly reapplying
leachate to waste masses saves offsite disposal costs and boosts landfill gas production.
2. Biological treatment
The high concentration of volatile fatty acids (VFA) in leachate makes it easily
biodegradable. The common methods, such as aerated lagoons, activated sludge process, and
rotating biological contactors are used to remove BOD, ammonia, and suspended solids from
the leachate.

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 3. Physicochemical treatment
Physiochemical processes are generally carried out to remove different substances,
such as heavy metals and other chemicals that remain even after the biological degradation of
leachate. These processes include flocculation-precipitation, adsorption, and reverse osmosis.
Recycling Programmes
Recycling programs are formulated and carried out according to the needs and
priorities of the communities. The major elements of a recycling program include source
separation, curbside collection, material resource facilities, and full stream processing.
1. Source separation
The segregation of recyclable and reusable materials at the point of generation is
referred to as source separation. It involves voluntary or mandated separation of recyclable
materials into their own specific containers.
2. Curbside collection
Kerbside collection or curbside collection is a service provided to households for
collecting source- separated recyclables on a regular basis. Specific purpose-built vehicles are
used to pick household waste in containers prescribed by the municipality. Kerbside
collection is today often referred to as a strategy of local authorities to collect recyclable
items from the consumer
3. Material recovery facilities (MRF)
MRF is a specialized plant that receives, separates, processes and markets recyclable
materials. Generally, two different types of material recovery facilities are in use:
1. Clean MRF
A clean MRF accepts source-separated materials from municipal solid waste
generated by either residential or commercial sources. In a single-stream type of clean MRF
processing, all recyclable materials are mixed. Whereas in dual-stream MRFs, source-
separated recyclables are delivered in a mixed container stream (glass, ferrous metal,
aluminum and other non-ferrous metals, and plastics) and a mixed paper stream (corrugated
cardboard boxes, newspapers, magazines, office paper, and junk mail).
2. Dirty MRF
A Dirty MRF or Mixed-waste processing facility (MWPF) involves the manual and
mechanical separation of recyclable materials from a mixed solid waste stream. MWPFs can
recycle wastes at much higher rates than that of curbside or other waste collection systems,
and it can recover 5% - 45% of the incoming materials as recyclables, then the remainder is
sent to landfills.

Recycled
Process
Material

The waste glass cullet is sorted according to the color and melted in an oven at
Glass
1400°C. Substances such as soda ash, potassium carbonate, borax, lime, etc., are
added to enhance the hardness of glass. It is followed by refining and molding

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 steps to finally yield new, clear, green and brown glass jars and bottles.

Ferrous and non-ferrous metals are usually recycled into sanitary and gas
fittings, funnels, buckets and storage bins, reinforced steel bars, hand tools, etc.
They are initially melted in a crucible in the coal furnace and the molten metal is
Metals
cast into the desired mold to make ingots of required shapes and size. New and
melted recycled metals are mixed together in a 3:1 ratio for better quality
products.
High-density polyethylene (HDPE) and polyethylene terephthalate (PET)
plastics now hold a stronger place in the market. The uses of recycled HDPE
Plastic include non-food bottles, drums, toys, pipes, sheets, and plastic pallets, and of
PET include plastic fibers, injection molding, non-food grade containers, and
chemicals.
Battery recycling is paramount due to the concerns over toxic compound
including lead, cadmium, and mercury present in many batteries. Battery
Batteries reprocessing includes breaking open the batteries, neutralizing the acid,
chipping the container for recycling and smelting the lead to produce recyclable
lead.

Single cell protein (SCP)

Research on the concept of SCP production began during the 1960s by some oil
companies when petroleum was inexpensive and appeared to be economically an attractive
substrate for SCP growth. The term SCP is used today to include “a microbial biomass, from
uni as well as multicellular microorganisms which can be use as food as such or as a feed
additive”. Microbes used for SCP production include algae, bacteria, yeasts and filamentous
fungi. Mushroom cultivation, where basidiocarps of the fungus are eaten as such are also
included in SCP. Because of their rapid growth, high protein content and ability to utilize a
range of organic substrates of low cost and even some industrial and agricultural wastes,
microbes are potentially valuable source of animal food. The proteins of selected microbes
contain all the essential amino acids. On an average, the microbial biomass contains about 45
to 55% protein and other essential nutrients as such. Thus SCP production has several
advantages over traditional methods of protein production for food and feed. In addition to
the above mentioned characteristics of microbes (rapid growth, high protein content and
potential of utilizing a range of low cost substrates), this method is independent of seasonal
and climatic conditions. Rapid conversion rate by microbes should be clear from that a
bullock weighing 500 kg produces about 0.4 kg of protein in 24 hours, whereas under
favourable conditions, 500 kg of yeast produce over 50,000 kg of protein in the same period.
Both autotrophs and heterotrophs are used in SCP. For instance, algae like Chlorella,
Scenedesmus, Spirulina etc. have been grown in various warm ponds as a food source. Use
of solar energy by these autotrophs reduces the amount of fuel resources required for SCP.
The alga, Spirulina is cultured, dried, powdered and used as tablets. It contains 60% proteins,
vitamins and unsaturated fatty acids. Among heterotrophs, mushrooms are being cultivated
world over on different solid substrates including agricultural wastes (as straw and compost)
employing SSF (solid state fermentation) technology.

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 Yeasts are excellent candidates for commercial SCP, yeast-based SCP has a high
vitamin content. Various yeasts, including species of Saccharomyces, Candida and
Torulopsis can be grown on waste materials, recycling these into useful sources of food.
Production of bacteria from petroleum
SCP can also be generated by growing the methylotroph, Methylophilus
methylotrophus (a bacterium that grows on C1 compounds), on methanol in a single huge
fermentor. The bacterium is grown on methanol, derived from methane, and the cell crop is
harvested, centrifuged, dried and sold in pellet or granular form. The SCP product is
marketed as Pruteen.
Fuels
Synthetic fuels produced by microbes should help meeting energy-crisis world over.
Useful fuels produced by microbes include ethanol, methane, hydrogen and hydrocarbons.
Right strains are able to do the job. For microbial production of fuels, waste materials such as
sewage and municipal garbage are used as fermentation substrates.
Ethanol
Ethanol production by microbes has become very popular in those areas where plant
residues (agricultural and other wastes) are available in abundance. Brazil produces and uses
large amounts of ethanol as automotive fuel, Gasohol, a 9: 1 blend of gasoline and ethanol,
has become popular fuel in USA. Despite some problems with the ethanol-fuel, several
processes are employed for its commercial production. The most efficient microbes are
Zymomonas mobilis (fermenting carbohydrate and producing alcohol twice as rapidly as
yeasts) and Themoanaerobacter ethanolicus, a thermophilic bacterium. Corn sugar and plant
starch are used as substrates. A two-step fermentation is used for conversion of cellulose to
ethanol, (i) conversion of cellulose to sugars, generally by Clostridium spp, followed by (ii)
conversion of these sugars to ethanol by yeasts, Zymomonas or Thermoanaoerobacter spp.
Methane
Methane produced by methanogenic bacteria is also another potential energy source.
Methane is used for generation of mechanical, heat and electrical energy. Anaerobic
decomposition of waste materials produces large amounts of methane. Many sewage
treatment plants produce this fuel. Efficient generation of methane can be achieved by using
algal biomass grown in pond cultures, sewage sludge, municipal refuse, plant residue and
animal waste. Methanogens (archaebacteria) are obligate anaerobes and produce CH4 by
reducing acetate and/or CO2.

Biogas, a mixture of different gases is produced by anaerobic microbes using

domestic and agricultural wastes. Bulk (about 50 – 70%) of biogas is methane (CH4) and
other gases are in low proportions. These include CO2 (25 – 35%), H2 (1 – 5%), N2 (2 – 7%)
and O2 (0 – 0.1%). In India a large number of gobar gas plants are already in operation in
rural areas. Left overs of these plants are good fertilizer also. Animal waste is first hydrolysed
by hydrolytic bacteria. It is followed by acid formation by a group of acetogenic bacteria,
which convert monomers into simple compounds like NH3, CO2 and H2. Finally
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methanogens reduce acetate and/or CO2 to CH4. In India, cattle dung is the chief source of
biogas.
Other fuels include hydrogen, that could be developed as a major fuel produced by
microbes in future. Photosynthetic microbes produce H2. They are able to convert solar
energy into a fuel that can be stored. The photoproduction of hydrogen is very attractive.
Some higher molecular weight hydrocarbon are produced by some algae. However, a
thorough under standing of basic mechanisms of microbial hydrocarbons formation and the
formation of petroleum deposits should permit the development of genetically engineered
microbes and fermentation processes to produce synthetic sources of petroleum
hydrocarbons.
Hazardous Wastes: These are the wastes which poses a threat or risk to public health, safety
and environment. The Hazardous waste can be further classified as under.
(i) Ignitable: Hazardous waste that is classified as ignitable includes the following:
 Liquids with a flashpoint of less than 60°C/140°F
 Solids that burn spontaneously
 Flammable compressed gas
 Oxidizers
(ii) Toxic: Wastes containing one or more of 39 specified contaminants.
(iii) Reactive: Waste that is classified as reactive includes the following:
 Materials that tend to be unstable at normal temperatures and pressures
 Water reactive materials
 Explosives
 Cyanide or sulfide bearing wastes
(iv) Corrosive: Waste that is classified as corrosive includes:
 Aqueous solutions with pH less than 2 or greater than 12.5
 Liquid that corrodes steel at a rate greater than 6.35 mm per year (0.25 inches per
year) at a test temperature of 55°C (130°F).
Due to their high toxic character hazardous waste require special precaution in its storage,
collection, transportation, treatment or disposal. A hazardous waste management plan should
comprehensively take care of all aspects from start to finish.
The important steps of the hazardous waste management plan includes the following:
 Inventorising generation and ensuring that every kg of hazardous waste generated is
accounted.
 Ensuring proper storage and transport of hazardous waste
 A disaster management plan for taking care of unexpected spillage or spread of
contaminants.
 Setting up of special treatment plants for chemical and physical treatment of hazardous.

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Treatment and Disposal
Treatment and disposal consists of physical, chemical and biological methods. The
physical methods involve pretreatment of hazardous waste using physical unit operations like
filtration, sedimentation, floatation, distillation, absorption and certain membrane processes
like dialysis and reverse osmosis.
The chemical processes involve chemical conversions which reduces the toxicity or
reactive potential of the wastes. Some examples are oxidation, reduction, precipitation, ion
exchange, neutralization etc. Biological processes like aerobic and anaerobic processes,
bacterial leaching are also in use. Offsite disposal methods include common waste treatment
facilities co disposal with municipal waste and use of secure landfill. In common hazardous
waste treatment facilities, incineration, pyrolysis, detoxification, neutralization etc. can be
carried our and the waste is further concentrated, stabilized and solidified and ultimately
disposed as a landfill. In co-disposal technique relatively small quantities of hazardous
materials are mixed with large volumes of municipal waste so that the contaminants are
diffused and diluted.
A secure landfill is a sophisticated repository for hazardous waste. In a secure landfill
the wastes are encased in more or less impermeable boundaries. The bottom of the landfill is
lined with synthetic materials over which a layer of compacted clay is applied. After filling
the waste the secure landfill is covered with synthetic membranes and clay covers. The land
fill depth should be such that it is atleast 1.5 meters above the ground water table. Proper
provisions for venting of gases generated, leachate collection and monitoring, Ground water
and air pollution monitoring are to be done.

Secure Landfill
Landfill Sections
Landfills may have different types of sections depending on the topography of the
area. The landfills may take the following forms: (a) above ground landfills (area landfills);

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(b) below ground landfill (trench landfills); (c) slope landfills; (d) valley landfills (canyon
landfills); and (e) a combination of the above.
Above Ground Landfill (Area Landfill): The area landfill is used when the terrain is
unsuitable for the excavation of trenches in which to place the solid waste. High-groundwater
conditions necessitate the use of area-type landfills. Site preparation includes the installation
of a liner and leachate control system. Cover material must be hauled in by truck or
earthmoving equipment from adjacent land or from borrow-pit areas.
Below Ground Landfill (Trench Landfill): The trench method of landfilling is ideally
suited to areas where an adequate depth of cover material is available at the site and where
the water table is not near the surface. Typically, solid wastes are placed in trenches
excavated in the soil. The soil excavated from the site is used for daily and final cover. The
excavated trenches are lined with low-permeability liners to limit the movement of both
landfill gases and leachate. Trenches vary from 100 to 300 m in length, 1 to 3 m in depth, and
5 to 15 m in width with side slopes of 2:1.
Slope Landfill: In hilly regions it is usually not possible to find flat ground for landfilling.
Slope landfills and valley landfills have to be adopted. In a slope landfill, waste is placed
along the sides of existing hill slope. Control of inflowing water from hillside slopes is a
critical factor in design of such landfills.
Valley Landfill: Depressions, low-lying areas, valleys, canyons, ravines, dry borrow pits etc.
have been used for landfills. The techniques to place and compact solid wastes in such
landfills vary with the geometry of the site, the characteristics of the available cover material,
the hydrology and geology of the site, the type of leachate and gas control facilities to be
used, and the access to the site. Control of surface drainage is often a critical factor in the
development of canyon/depression sites. It is recommended that the landfill section be
arrived at keeping in view the topography, depth to water table and availability of daily cover
material.
E waste
India stands fifth in e-waste generation producing around 1.7 lakhs metric tonnes per
annum. Obsolete, dysfunctional and discarded computers and computer peripherals,
televisions, VCRs, DVD players, stereo equipment, and cell phones and other electronic and
instrumentation gadgetry are commonly referred to as electronic waste or e-waste.
Management and disposal of e-waste has become a serious problem in recent times due to a
surge in the use of these items and the rate at which they become obsolete. Electronic waste
in addition to occupying valuable landfill space is also hazardous in nature. One of the major
pollutant in the electronic waste is lead which may cause lead poisoning and can be
especially harmful to young children.

 Only 22.7 per cent of the e-waste out of the total 10, 14,961.21 tonnes generated in
2019-20 in India was collected, dismantled, and recycled or disposed off.
 This e-waste is composed of 21 types of electrical and electronic equipment (EEE)
notified Under the E-Waste (Management) Rules, 2016.
 The E-Waste (Management) Rules, 2016 extend the responsibility to producers to
manage a system of e-waste collection, storage, transportation, and environmentally
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 sound dismantling and recycling through Extended Producer Responsibility (EPR)
authorisation.
 The rules also promote and encourage the establishment of an efficient e-waste
collection mechanism.
 India is the world’s third largest generator of e-waste after China and the US,
according to the UN Global E-Waste Monitor Report.
 Maharashtra generates the most e-waste among all the Indian states.
 Uttar Pradesh, Uttarakhand, Tamil Nadu, and Haryana are among the States that have a
bigger capacity to dismantle and recycle e-waste.
 E-waste typically does not feature in the list of municipal solid waste and therefore it is
not a direct mandate for the cities to collect, transport, and manage them.
Much of the focus on managing e-waste revolves around Cathode Ray Tubes (CRTs),
often called “picture tubes,” which convert an electronic signal into a visual image. Computer
monitors, televisions, some camcorders, and other electronic devices contain CRTs. A typical
CRT contains between two and five pounds of lead.
E-waste disposal and management
E-waste can be managed in various ways, depending upon its continued usability,
availability of reprocessing facilities, where it is generated, and other factors. Here are some
options:
Reduce: The principle of reducing waste, reusing and recycling resources and products is
often called the "3Rs." Reducing means choosing to use things with care to reduce the
amount of waste generated.
Recycle: Preventing waste in the first place is the preferred management option. Consider
repairing or upgrading your used electronic equipment so you can continue to use it. In some
cases, for example, adding memory to a computer or upgrading software can improve the
units’ performance and extend its usefulness. Instead of purchasing a new digital television,
consider purchasing a converter box to receive and reformat DTV signals.
Donate: Donating reusable electronic equipment to schools or other nonprofit organizations.
Reuse: In response to consumer concerns, several electronics manufacturing companies have
implemented take-back programs. Some programs allow the purchaser to pay a fee at the
time of sale to cover shipping to a reprocessing facility when the unit becomes unwanted or
obsolete. Others allow owners to ship e-waste to their facilities for a nominal fee or will
provide owners with a rebate when the unit is shipped to a participating recycling center.
Some waste management companies also offer similar management options to households
and businesses. Units may be reused or dismantled for recycling. The silver, gold, lead and
other heavy metals as well as some of the plastics and glass are recycled. Some companies
guarantee 100% of the unit is recycled while others recycle as much as possible and then
dispose of the rest.
Dispose: E wastes are disposed as secure landfill since the waste is considered to be as
hazardous due to the presence of heavy metals. Pretreatment of the waste is necessary to
reduce volume occupied. Size reduction techniques like crushing and grinding or mechanical
compaction is used.

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 The compacted waste is encased in synthetic membrane containers and are placed
inside a secure landfill.
Fly Ash
Fly Ash is the fine particulate residual outcome of pulverized coal burning obtained
primarily from the coal-based electricity generation plants. Considering the exponential
increase in population around the world, the electrical energy demand as of now is at an all-
time high and coal-based power plants are responsible for satisfying major part of this
demand especially in developing countries. Owing to this extra load on coal-based plants,
there is a significant increase in the production of fly ash from these plants and the disposal
of fly ash which is considered a deleterious product for environment is becoming a concern
for everyone.
Since 1920, coal is being used as a basic fuel for power generation and billions of tons
of fly ash and other by-products have been created till now and the improper disposal of these
by-products has had a considerable negative influence on the environment. Fly ash, if not
managed properly pollutes water, air and soil, however the recent advancements in
engineering have made it a useful resource in many areas especially in construction industry.
When pulverised coal is placed in combustion chamber of boiler it immediately ignites
producing mineral residue which is in molten state. After extracting heat from the boiler, the
molten residue cools, hardens and ash is formed. The coarser part of this residue referred to
as bottom ash falls to the bottom of combustion chamber while as the finer ash particles
remain suspended within the flue gas and these finer particles are removed by particulate
emission control devices like electrostatic precipitors (ESPs). The Indian coal is low grade
and has high ash content (30-45%) as compared to imported coals (10-15%), so large
quantities of fly ash are generated, 217.04 Million tons in 2018-19. The generated fly ash
requires large areas for disposal as well as remains a source of environmental pollution.
Fly Ash Properties: Physically, fly ash occurs as very fine particles having minute
average diameter, and has low to medium bulk density, high surface area and light texture.
Chemically, Fly Ash is considered as amorphous and mixture of Ferro-alluminosilicate
minerals. However, the chemical and physical properties of fly ash depend on the type of coal
used, combustion methodology adopted, and temperature regulation during combustion and
method of collection. Following are some of the physical and chemical properties of fly ash:
 Even though there is some degree of variability of constituents owing to the
variation in coal source, however, more often the primary constituents are SiO2,
CaO, Al2O3, Fe2O3 along with some amounts of MgO, Na2O, etc.
 Fly ash particles generally fall in silt range and are typically finer as compared to
lime and Portland cement.
 The size of fly ash particles varies from 10 to 100 microns having a spherical shape.
 Colour of fly ash principally depends on the mineral composition of coal source, it
may have a dark or black shade or tan colour.
 The specific gravity of fly ash depends on the degree of coal pulverization, particle
shape, and coal type. It varies considerably from 1.6 to 3.1.

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  Fly ashes sourced from bituminous coals tend to be acidic and those from sub-
bituminous tend to be alkaline, this is heavily dependent on the chemical
composition of ash.
Even though fly ash has greater surface area but the Cation Exchange Capacity (CEC)
is on the lower side due to the non-plastic nature, however, CEC can be increased by
modifying the fly ash. Also, lower CEC signifies lesser water absorption and this property
can be and has been used favourably while stabilizing expansive soils.
Fly Ash Classification
 Class C Fly Ash has high cementing abilities and these are formed from the burning
of subbituminous coal. This kind of fly ash has lime in excess of 20% and also does
not need an activator (based on ASTM C 618 standards) for the formation of
cementitious compounds.
 Class F Fly Ashes are generated from the combustion of bituminous and anthracite
coals. These ashes have less than 10% lime content and need an activator (based on
ASTM C 618 standards) like Portland cement, quick lime, etc. for the formation of
cementitious compounds.
Fly Ash Production and Utilization in India
As of now, in India 72% of the total electricity is produced by the coal-based
electricity generation plants and this production rate and dependence on such plants is
expected to remain the same in the coming years. The fly ash generation during 2018-19 was
217.04 million tonnes due to combustion of 667.43 million tonne Coal/Lignite and fly ash
utilization was around 168.40 million tonne which suggests an effective usage of 77.59%
respectively. Presently, fly ash is used in the construction industry on a large scale like in the
manufacturing of Portland pozzolana cement, construction of roads, dams, stabilization of
slopes, etc.
Utilization of Fly Ash in diverse field
 Utilization of fly ash in construction industry
 Usage of fly ash in portland cement concrete
 Usage of fly ash in building materials like brick
 Fly ash in stabilized base course
 Fly ash in pavements
 Application of fly ash in agriculture: Soil properties, as influenced by fly-ash
application, have been studied by several workers for using it as an agronomic
amendment. Physical and chemical properties of soil due to fly-ash amendment vary
according to the original properties of soil and fly ash and therefore, the mode of use in
agriculture is different and depends on the characteristics of soil or soil type According
to the CEA 2018-19 report, agriculture use of fly ash is 1.38 billion tons’ sums up to
0.63% of total fly ash generation.
 Fly ash utilization with special reference to geotechnical engineering

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  Fly ash mix as a replacement for earthen/sand backfilling
 Fly ash utilization in fills/embankments
 Fly ash for stabilization of expansive soils
Environmental benefits: Fly ash utilization, especially in concrete, has significant
environmental benefits including:
 Increasing the life of concrete roads and structures by improving concrete durability
 Net reduction in energy use and greenhouse gas and other adverse air emissions when
fly ash is used to replace or displace manufactured cement
 Reduction in amount of coal combustion products that must be disposed in landfills
 Conservation of other natural resources and materials.
Disposal of Fly Ash Notification (1999) the main objective of which is to conserve the
topsoil, protect the environment and prevent the dumping and disposal of fly ash discharged
from lignite-based power plants. The salient feature of this notification is that no person
within a radius of 50 km from a coal-or lignite-based power plant shall manufacture clay
bricks or tiles without mixing at least 25% of ash with soil on a weight-to-weight basis.
Plastic wastes
As per the annual report of the Central Pollution Control Board (CPCB) for the year
2018-19, India produced over 3.3 million metric tonnes of plastic, an increase of over more
than 1 million metric tonnes compared to 2017-18; the major generation came from
Maharashtra (12%), Tamil Nadu (12%), Gujarat (11%), West Bengal (9%), Uttar Pradesh
(8%), Karnataka (8%) and Delhi (7%). The 4,773 registered plastic recycling units, including
7 biodegradable facilities, and 1,084 unregistered plastic recycling enterprises, were
employed to manage such a massive amount of plastic rubbish (CPCB 2019). 60 per cent of
all manufactured plastic is recycled. The remaining 40 per cent of plastic becomes waste if it
is not cleaned and segregated, and it is either landfilled or pollutes streams or groundwater
resources. India, a rapidly rising non-industrial country with a population of 137 billion
people, ranks twelfth in the world economy in terms of GDP (Gross Domestic Product).
Furthermore, India ranked third in the world in terms of PPP (purchase power product) (US
EPA 2015).
Plastics are classified as thermoplastics or thermosetting plastics based on how their
physical and chemical properties change before and after heat treatment. Thermoplastics are
heat-susceptible plastics such as polyethylene (PE), polyvinyl chloride (PVC), polypropylene
(PP), polystyrene (PS), polycarbonate (PC), and polytetrafluoroethylene (PTFE) can be
softened or melted into any shape under heating conditions and solidified when cooled, which
can be repeatedly deformed with typical plasticity. Thermosetting plastics such as epoxy
resin, phenolic resin, urea formaldehyde resin, and organo silicon resin do not undergo plastic
deformation when heated; instead, they would decompose when the temperature continues to
rise between 250-300 ⁰C. Thermoplastics account for up to 80 per cent of all plastics
produced worldwide, while thermosets account for the remaining 20 per cent. Thermoplastics
are easily recyclable and pose no risk, whereas thermoset plastics such as epoxy resin and
polyurethanes are not. Clear polyethylene terephthalate (PET) bottles and natural high-
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density polyethylene (HDPE) bottles can be recycled successfully, while PVC, PS, and PP
are not routinely recycled from post-consumer waste. Approximately 50 per cent of plastics
are used for single-use disposable applications, such as packaging, agricultural films, and
disposable consumer items, and between 20 and 25 per cent for long-term infrastructures,
such as pipes, cable coatings, and structural materials, and the remainder for durable
consumer applications with intermediate lifespan, such as electronic goods, furniture,
vehicles, and so on, and are made of PVC, PS, or PP, which have low recycling rates and thus
are not suitable for reuse; thus contributing significantly to plastic waste. India's plastic waste
processing capability is only 15 per cent of the total waste generated, and because it is a land-
scarce country with a high population density, dump yards, and landfill sites are
overburdened.

Phasing out or ban Encouraging the use of

single use plastics less ecofriendly and
than 100 microns biodegradable products

Promoting innovations
Incentivize the
like bioplastics and
business of recycling
PVAs for packaging

Making rules and Plastic waste Segregate the waste at

guidelines for EPR
Management source
simple and enforeable

 Reused plastic wastes in construction purposes

 Recycling of PET bottles into textile fibers
 Biodegradable Leaf plates as an alternative to disposable plastic plates
 Bamboo as an alternative to plastic bottles
 PVA as an alternative to plastic packaging

Role of bioplastics

Bioplastics are polyesters manufactured by a range of microorganisms cultivated

under varying nutrient and environmental conditions. These polymers are mainly lipid-based
and are collected as storage resources (in the form of mobile, amorphous, liquid granules),

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facilitating microbial survival in stressful situations. Among the many biopolymers,
polyhydroxyalkanoates (PHAs) have received interest for industrial-scale manufacturing not
only due to their biodegradability and compostable features but also due to their facile
conversion to diverse forms, possessing required characteristics as plastic materials. PHA is
the only bioplastic that is entirely produced by microorganisms, with more than 30 per cent
produced by soil-inhabiting bacteria. Many microorganisms in activated sludge, on high seas,
and in the harsh cold environment are also capable of generating PHA. In the last 10 years,
PHA has been developed fast enough to find applications in numerous fields. Best researched
microorganisms include Ralstonia, Pseudomonas, Halomonas, Burkholderia,
Rhodospirillum, etc. able to utilize a variety of carbon sources and create different forms of
PHA.
The stressed environment of salinity off the Gujarat coast, India in which the cyanobacteria
Spirulina subsalsa thrives nearly overrides the contamination problem and can minimize the
sterility requirements of a production facility, thus, decreasing the investment cost. The
possible use of these microalgae for PHA generation from sludge, industrial effluent, or other
wastewater which has a high salt content can be the way forward. The capacity of Spirulina
subsalsa to flourish in salinity makes them ideal for industrial and bioremediation
applications.
THE 5 R'S: Refuse, reduce, reuse, repurpose, recycle

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