solid waste recycling lectures.pptx

WHAT IS Municipal SOLID WASTE?
• Any material that is thrown away or discarded as
useless and unwanted is considered solid waste

BACKGROUND HISTORY
• Non-existence of any National or Provincial Laws
• Solid waste Management in Pakistan is developing into an increasingly complex job
• Solid Waste Generation Rate in Pakistan Ranges between 0.283 to 0.612
Kg/Capita/Day
• Waste Generation Growth Rate is 2.4 % per year
• Collection capacity of concerned districts is lesser than the amount generated daily
• There is no proper collection of solid waste collection and Disposal System
• 54,850 tons of solid waste is generated daily
• 60 % of municipal solid waste is collected while rest remains unattended

Municipal Solid Waste
Refuse
Trash
Garbage
Highly Decomposable Food Waste
e.g. Vegetable & meat Scraps
Rubbish
Non-decomposable
Combustible
Routine Collection
A-periodic Collection
e.g old couch, tv ,
refrigerator
Waste Processing Energy
Recovery Recycling
Final Disposal
(Land Fill)
MUNICIPAL SOLID WASTE CLASSIFICATION

TYPES OF SOLID WASTES
TYPES OF SOLID
WASTE
ORGANIC INORGANIC
Agriculture Waste Kitchen Waste
Silicates, mica
Asbestos, chemicals
etc

Sources and Types of Solid Wastes
 Sources of solid wastes in a community are:
• Residential
• Commercial
• Institutional
• Construction and Demolition
• Municipal Services
• Treatment Plant Sites
• Industrial
• Agricultural

 MSW includes all the community waste with the exception of industrial
process waste and agriculture wastes
 It is important to define the various types of solid wastes that are
generated and the sources to design and operate the functional elements
associated with the management of solid waste.

Types of solid wastes
Typical facilities,
activities, locations where
wastes are generated
Source
Food wastes, paper, cardboard, plastics,
textiles, leather, yard wastes, wood,
glass, metals, ashes, special wastes
(e.g., bulky items, consumer
electronics, white goods, batteries, oil,
tires), and household hazardous wastes
Single and multifamily
dwellings
Residential
Industrial process waste, scrap
materials, etc. Non - industrial waste
including food wastes, construction and
demolition wastes, rubbish, ashes ,
hazardous wastes, ashes, special wastes
Light and heavy
manufacturing, fabrication,
construction sites, power
and chemical plants
Industrial
Table 1: Sources and Types of Solid Wastes within a Community

Typical facilities,
activities, locations where
wastes are generated
Source
Paper, cardboard, plastics, wood, food
wastes, glass, metals, special wastes,
hazardous wastes
Stores, hotels, restaurants,
markets, office buildings,
etc.
Commercial
Same as commercial
Schools, hospitals, prisons,
government centers
Institutional
Wood, steel, concrete, dirt, etc.
New construction sites,
road repair, renovation
sites, demolition of
buildings, broken pavement
Construction and Demolition
Table 1: Sources and Types of Solid Wastes within a Community (Cont’d)

Table 1: Sources and Types of Solid Wastes within a Community (Cont’d)
Typical facilities, activities,
locations where wastes are
generated
Source
Street sweepings; landscape and tree
trimmings; general wastes from parks,
beaches, and other recreational areas;
sludge
Street cleaning, landscaping,
parks, beaches, other
recreational areas, water and
wastewater treatment plants
Municipal
Services (excluding
treatment facilities)
Spoiled food wastes, agricultural wastes,
rubbish, hazardous waste.
Field and row crops, orchards,
vineyards, dairies, feedlots,
farms, etc.
Agricultural

Nature of Municipal Solid Waste
 Organic (Combustible)
 Inorganic (non-combustible)
 Putrescible
 Recyclable
 Hazardous
 Infectious

Composition of Solid Waste
The percentage distribution values for the components in MSW
vary with
 Location
 Season
 economic conditions
 population
 Social behavior
 Climate
 Market for waste materials
 Other factor

•The proportion of paper waste increases with increasing
national income; the proportion of putrescible organic matter
(food waste) is greater in countries of low income than those
of high income.
•Variation in waste composition is more dependent on national
income than Geographical location, although the latter is also
significant.
• Waste density is a function of national income, being two to
three times higher in the low-income countries than in
countries of high income.
• Moisture content is also higher in low-income countries; and
the composition of waste in a given urban center varies
significantly with socio-economic status (household income).

Physical Characteristics
• Density: Density i.e. the mass per unit volume (kg/m3) is as critical in the
design of a sanitary landfill as it is for the storage, collection and
transportation of waste. Efficient operation of a landfill requires compaction
of the waste to optimum density after it is placed.
• in high income countries, considerable benefit is derived through the use of
compaction vehicles on collection routes, because the waste is typically of
low density.
• A reduction of volume of 75% is frequently achieved with normal
compaction equipment, so that an initial density of 100 kg/m3 will readily
be increased to 400 kg/m3.

• In other words, the vehicle would haul four times the weight of waste in
the compacted state than when the waste is uncompacted.
• The situation in low-income countries is quite different: a high initial
density of waste precludes the achievement of high compaction ratio.
Consequently, compaction vehicles offer little or no advantage and are not
cost-effective.

Moisture Content
• Moisture content of solid wastes is usually expressed as the weight of
moisture per unit weight of wet material.
• Moisture Content (%) =
• Wet weight – dry weight
------------------------------ X 100
• Wet weight

• A typical range of moisture contents is 20 – 45% representing the extremes of
wastes in an arid climate and in the wet season of a region having large
precipitation. Values greater than 45% are however not uncommon.
• Moisture increases the weight of solid waste and therefore the cost of
collection and transport. Consequently, waste should be insulated from
rainfall or other extraneous water.
• Moisture content is a critical determinant in the economic feasibility of waste
treatment and processing methods by incineration since energy (e.g. heat)
must be supplied for evaporation of water and in raising the temperature of
the water vapour.
• Climatic conditions apart, moisture content is generally higher in low income
countries because of the higher proportion of food and yard waste.

Chemical Characteristics
A knowledge of chemical characteristics of waste is essential in determining the efficacy of
any treatment process. Chemical characteristics include (i) chemical; (ii) bio-chemical; and
(iii) toxic.
• Chemical: Chemical characteristics include pH, Nitrogen, Phosphorus and Potassium (N-P-
K), total Carbon, C/N ratio, calorific value.
• Bio-Chemical:, Bio-Chemical characteristics include lipids, carbohydrates, proteins natural
fibre, and biodegradable factor.
• Toxic: Toxicity characteristics include heavy metals, pesticides,insecticides, Toxicity test for
Leachates (TCLP), etc. The waste may include lipids as well.

Calorific Value
• Calorific value is the amount of heat generated from combustion of a unit weight of a
substance, expressed as kcal/kg.
• While evaluating incineration as a means of disposal or energy recovery, the following
points should be kept in view:
• Organic material yields energy only when dry;
• The moisture contained as free water in the waste reduces the dry organic material
per kilogram of waste and requires a significant amount of energy for evaporation.
• The average MSW in developed countries has a calorific value between 8 and 12
MJ/kg. Based on this property the MSW can be compared with the fresh wood or
lignite, which is low grade coal.
• Developing countries in general produce more wet waste with lower calorific value
but if dried it can easily reach above calorific values.

A knowledge of the classes of chemical compounds and their
characteristics is essential in proper understanding of the
behaviour of waste as it moves through the waste management
system. The product of decomposition and heating values are two
examples of the importance of chemical characteristics. Analysis
identifies the compounds and the per cent dry weight of each
class.
Calorific value indicates the heating value of solid waste. Chemical
characteristics are very useful in assessment of potential of
methane gas generation. The various chemical components
normally found out in municipal solid waste are described below.

• (i) Lipids:
• Included in this class of compounds are fats, oils and grease. The
principal sources of lipids are garbage, cooking oils and fats. Lipids
have high calorific values, about 38000 kcal/kg, which makes waste
with a high lipid content suitable for energy recovery processes.
•
• Since lipids in the solid state become liquid at temperatures slightly
above ambient, they add to the liquid content during waste
decomposition. They are biodegradable but because they have a low
solubility in waste, the rate of biodegradation is relatively slow.

• Carbohydrates: Carbohydrates are found primarily in food and yard waste. They include
sugars and polymers of sugars such as starch and cellulose and have the general formula
(CH2O)X. Carbohydrates are readily biodegraded to products such as carbon dioxide,
water and methane. Decomposing carbohydrates are particularly attractive for flies and
rats and for this reason should not be left exposed for periods longer than is necessary.
• Proteins: Proteins are compounds containing carbon, hydrogen, oxygen and nitrogen
and consist of an organic acid with a substituted amine group (NH2). They are found
mainly in food and garden wastes and comprise 5-10% of the dry solids in solid waste.
Proteins decompose to form amino acids but partial decomposition can result in the
production of amines, which have intensely unpleasant odours.

Natural Fibres:
This class includes the natural compounds, cellulose and
lignin, both of which are resistant to biodegradation. They are
found in paper and paper products and in food and yard
waste. Cellulose is a larger polymer of glucose while lignin is
composed of a group of monomers of which benzene is the
primary member.
Paper, cotton and wood products are 100%, 95% and 40%
Cellulose, respectively. Since they are highly combustible, solid
waste having a high proportion of paper and wood products,
are suitable for incineration. The calorific values of oven dried
paper products are in the range 12000 – 18000 kcal/kg and of
wood about 20000 kcal/kg, which compare with 44200 kcal/kg
for fuel oil.

Synthetic Organic Materials (Plastic):
In recent years, plastics have become a significant component
of solid waste accounting for 5-7%. Plastic being non-bio
degradable, its decomposition does not take place at disposal
site. Besides, plastic causes choking of drains and
Environmental pollution when burnt under uncontrolled
condition. Recycling of plastics is receiving more attention,
which will reduce the proportion of this waste component at
Disposal sites.
Non-combustibles:
Materials in this class are glass, ceramic, metals, dust, dirt,
ashes and construction debris. Non-combustibles account for
30-50% of the dry solid.

4Rs of SWM
• Source reduction, reuse, recycling, composting, and energy recovery are all
examples of resource conservation.
• Resource conservation avoids GHG emissions from common waste management
pathways, including:
• Emissions from combustion: Waste incineration produces emissions of CO2 and
nitrous oxide, a GHG that is 310 times as potent as CO2.
• Emissions from transportation: Transporting waste to disposal sites produces GHG
emissions from the combustion of the fuel used in the equipment.
• Emissions from landfills. Waste in landfills decomposes anaerobically and produces
methane, a GHG that is 21 times as potent as CO2.

Factors That Contribute To the Solid Waste Generation

Solid Waste:
“Heterogenous mass of discarded material”
SOLID WASTE MANAGEMENT
The discipline associated with the control of generation, storage, collection, transfer and
transport, processing and disposal of solid waste in manner that is accordance with the best
principles of public health, economic, engineering, conservation, aesthetics and
environmental consideration.
INTEGRATED SOLID WASTE MANAGEMENT ?
The selection and application of suitable techniques, technologies and
management programs to achieve specific waste management objective and
goals

Classification of Wastes according to their
Properties
Bio-degradable
can be degraded (paper, wood, fruits and others)
Non-biodegradable
cannot be degraded (plastics, bottles, old machines,cans,
styrofoam containers and others)

Classification of wastes according to their
origin and type
• Municipal Solid wastes: Solid wastes that include household garbage, rubbish, construction
& demolition debris, sanitation residues, packaging materials, trade refuges etc. are
managed by any municipality.
• Bio-medical wastes: Solid or liquid wastes including containers, intermediate or end
products generated during diagnosis, treatment & research activities of medical sciences.
• Industrial wastes: Liquid and solid wastes that are generated by manufacturing & processing
units of various industries like chemical, petroleum, coal, metal gas, sanitary & paper etc.
• Agricultural wastes: Wastes generated from farming activities. These substances are mostly
biodegradable.
• Radioactive wastes: Waste containing radioactive materials. Usually these are byproducts of
nuclear processes. Sometimes industries that are not directly involved in nuclear activities,
may also produce some radioactive wastes, e.g. radio-isotopes, chemical sludge etc.
• E-wastes: Electronic wastes generated from any modern establishments. They may be
described as discarded electrical or electronic devices. Some electronic scrap components,
such as CRTs, may contain contaminants such as Pb, Cd, Be or brominated flame retardants.

SOURCES AND OTHER TYPES
OF WASTE
Source Typical Waste Generators Types of solid wastes
1:Residential Single and multifamily dwellings
 Food wastes
 Paper
 Cardboard
 Plastics
 Textiles
 Leather
 Yard wastes
 Wood
 Glass
 Metals
 Ashes
 Special wastes
(e.g bulky items, consumer electronics,
white goods, batteries, oil, tires), and
household hazardous wastes.)

2: Industrial Light and heavy manufacturing,
fabrication, construction sites, power
and chemical plants.
 Housekeeping wastes
 Packaging
 Food wastes
 Construction and demolition
materials
 Hazardous wastes
 Ashes
 Special wastes.
3:Commercial Stores, hotels, restaurants, markets,
office buildings, etc.
 Paper
 cardboard
 plastics
 wood
 food wastes
 glass
 metals
 special wastes
 hazardous wastes
4: Institutional Schools, hospitals, prisons, government
centers.
Same as commercial.
Made by Sahrish (BS Hons in Environmental Science)
International Islamic University, Islamabad

5:Construction and demolition New construction sites, road repair,
renovation sites, demolition of buildings
 Wood
 steel
 concrete
 dirt etc.
6:Municipal services Street cleaning, landscaping, parks,
beaches, other recreational areas, water
and wastewater treatment plants.
 Street sweepings
 landscape and tree trimmings
 General wastes from parks
 Beaches
 Recreational areas; sludge.
7:Process (manufacturing etc.) Heavy and light manufacturing,
refineries, chemical plants, power plants,
mineral extraction and processing.
 Industrial process wastes
 Scrap materials
 Off-specification products.
8:Agriculture Crops, orchards, vineyards, dairies,
feedlots, farms.
 Spoiled food wastes
 Agricultural wastes
 Hazardous wastes (e.g., pesticides).

Waste hierarchy refers to 3 Rs Reduce, Reuse, Recycle
Waste hierarchy

REUSE
- Reuse corrugated moving boxes internally.
- Reuse office furniture and supplies, such
as interoffice envelopes, file folders, and paper.
- Use durable towels, tablecloths, napkins,
dishes, cups, and glasses.
- Use incoming packaging materials for
outgoing shipments.
- Encourage employees to reuse office
materials rather than purchase new ones.
REDUCE
- Reduce office paper waste by implementing a
formal policy to duplex all draft reports and by
making training manuals and personnel
information available electronically.
- Improve product design to use less materials.
- Redesign packaging to eliminate excess
material while maintaining strength.
- Work with customers to design and
implement a packaging return program.
- Switch to reusable transport containers.
- Purchase products in bulk.

Solid Waste
Disposal Path
•Waste Collection
•Waste Reception &
Transfer
•Waste disposal
Solid Waste Disposal Methods
•Open dumping
•Sanitary landfill
•Incineration
•Composting
•Pyrolysis
•High-temperature
•Size reduction (shredding,
grinding pulverizing)

8R’s CONCEPT OF
WASTE MANAGEMENT

Waste hierarchy
Waste hierarchy refers to 4 Rs
Reduce, Reuse, Recycle and Recovery

Waste
• Minimizing solid waste
 Minimizing packaging
 Recycleable
Paper, plastics, metals, glass,
wood
 Reusable ?
Textiles, leather, rubber,
metals, wood
 Compostable
Yard trimmings, food scraps
(vegetable)

“By recycling almost 8 million tons of metals (which includes aluminum, steel, and mixed
metals), we can eliminate greenhouse gas (GHG) emissions totaling more than 26 million
metric tons of carbon dioxide equivalent (MMTCO2E). This is equivalent to removing more
than 5 million cars from the road for one year.”

It is estimated that food wasted by the US and Europe could feed the world
three times over.
Food waste contributes to excess consumption of freshwater and fossil
fuels which, along with methane and CO2 emissions from decomposing
food, impacts global climate change.
Every ton of food waste prevented has the potential to save 4.2 tones of
CO2 equivalent. If we all stop wasting food that could have been eaten, the
CO2 impact would be the equivalent of taking one in four cars off the road.

Recycling is the best way to solve solid waste management problem. This process
exists in all cities . However, the recycling system differs from developing countries
and developed countries .
 Developed countries have well organized source separation and recycling system
while in the developing countries the system of recycling is not effective because it
is still in the hands of informal sectors.

Types of Materials Recovered from MSW
 Aluminum
 Paper
 Plastics
 Glass
 Ferrous Metals (Iron and Steel)
 Nonferrous waste
Yard waste collected separately
 Construction and demolition wastes

Concept of Recycling
• Recycling is the method of transforming waste materials into new objects or
materials. In other words, recycling is the process of reusing materials instead
of throwing them away as waste.

Recycling- The only way the earth can became
survivable
• For centuries man has strived tremendously to make things easier,
without which life would’ve been such a mess. Recycling is one of
the many ways by which life on earth is made bearable. When the
things that are wasted and thrown away are processed and then put
to reuse, the phenomenon is known as recycling.
• Ability to recycle is the best kind of mercy that nature has ever had
on our environment. Without it, we all would be surviving in
landfills and incinerators and the world would’ve been a hub of
pollution and diseases, so much so that there would be time when
there wouldn’t be any safe place to live on earth with more garbage
and less people in any given locality.
• But now when industrialization has brought to the environment
mess and pollutants, it has also acquired ways to recycle which in
turn have controlled the pollution caused by the industries.

How does recycling prevent pollution?
• Since the processed products like plastics, metals etc. are
reprocessed, they don’t have to go through the manufacturing
process all over again, which as a result saves raw materials and
energy and prevents pollution.
• No smoke, land and sea waste is produced because no
manufacturing takes place and the polluting extraction process of
raw materials is omitted as well from the production process.
• It’s like we have the processed product in hand which causes harm
to the environment only for once and all during the production
cycle. Afterwards it will be of the same utility to the public and it
will drive the same profits and benefits without having to be
reproduced ever again but there is just the need to reprocess it
which hardly causes any pollution.

Recycling generates employment and saves
money
• The economy would suffer unemployment had not there been
recycling. This is because the waste management process requires
hundreds and thousands of dollars which would lead any industry
to economic depression. Today we’re saving money and at the
same time investing much lesson employing personnel and workers
to conduct recycling activities.

Initiative on the side of the State
• Due to recycling, people are encouraged not to litter.
Dust bins and garbage cans are placed everywhere with
the recycling sign (chasing arrow symbol). From trash, the
recyclable stuff is picked and reprocessed.

History of recycling
• Recycling is not new to the world. It dates back to the
time of Plato when worn out and broken pottery (ceramic)
items and tools were reused because there was dearth
(shortage) of raw materials. When recycling is as old as
Plato, it wouldn’t be wrong to say that people have always
been genius.

Initiatives on our part
• Now that we know recycling is one of the most profound achievements
of mankind, we must promote it to the best of our abilities.
• Do you know that the amount of energy which is saved on one recycled
glass bottle because of not having to reproduce it is sufficient to light a
bulb for four hours? Imagine how many hours of energy we’re saving on
daily basis. And of course, if we fully implement the recycling programs
in the world, including the underdeveloped countries, everything would
be so beautified and awesome without any trash and garbage.

Recycling Basics
• Recycling is the process of collecting and processing materials that
would otherwise be thrown away as trash and turning them into
new products. Recycling can benefit your community and the
environment.

Benefits of Recycling
• Reduces the amount of waste sent to landfills and incinerators
• Conserves natural resources such as timber, water and minerals
• Increases economic security by tapping a domestic source of materials
• Prevents pollution by reducing the need to collect new raw materials
• Saves energy
• Conserves valuable resources
• Helps create jobs in the recycling and manufacturing industries in the United
States

Steps to Recycling Materials
• Recycling includes the three steps below, which create a continuous loop,
represented by the familiar recycling symbol.
• Step 1: Collection and Processing
• There are several methods for collecting recyclables, including curbside
collection, drop-off centers, and deposit or refund programs.
• After collection, recyclables are sent to a recovery facility to be sorted, cleaned
and processed into materials that can be used in manufacturing. Recyclables are
bought and sold just like raw materials would be, and prices go up and down
depending on supply and demand in the United States and the world.

Step 2: Manufacturing
• More and more of today's products are being manufactured with recycled
content.
• Common household items that contain recycled materials include the
following:
• Newspapers and paper towels
• Aluminum, plastic, and glass soft drink containers
• Steel cans
• Plastic laundry detergent bottles
• Recycled materials are also used in new ways such as recovered glass in
asphalt to pave roads or recovered plastic in carpeting and park benches.

Step 3: Purchasing New Products Made
from Recycled Materials
• You help close the recycling loop by buying new products made from recycled materials. There are
thousands of products that contain recycled content. When you go shopping, look for the following:
• Products that can be easily recycled
• Products that contain recycled content
• Below are some of the terms used:
• Recycled-content product - The product was manufactured with recycled materials either collected from a
recycling program or from waste recovered during the normal manufacturing process. The label will
sometimes include how much of the content was from recycled materials.

• Post-consumer content - Very similar to recycled content, but the material comes only from recyclables
collected from consumers or businesses through a recycling program.
• Recyclable product - Products that can be collected, processed and manufactured into new products after
they have been used. These products do not necessarily contain recycled materials. Remember not all
kinds of recyclables may be collected in your community so be sure to check with your local recycling
program before you buy.
• Some of the common products you can find that can be made with recycled content include the following:
• Aluminum cans
• Car bumpers
• Carpeting
• Cereal boxes
• Comic books
• Egg cartons
• Glass containers
• Laundry detergent bottles
• Motor oil
• Nails
• Newspapers

Recycling Creates Jobs
• EPA released significant findings on the economic benefits of the recycling industry with an
update to the national Recycling Economic Information (REI) Study in 2016. This study
analyzes the numbers of jobs, wages and tax revenues attributed to recycling. The study
found that in a single year, recycling and reuse activities in the United States accounted for:
• 681,000 jobs
• $37.8 billion in wages (pay); and
• $5.5 billion in tax revenues.
• This equates to 1.17 jobs per 1,000 tons of materials recycled and $65.23 in wages and
$9.42 in tax revenue for every ton of materials recycled.

Solid Waste Reduction, Reuse and Recycling
• Introduction
• In every aspect of human life unwanted materials are generated and then discarded simply
because they are considered to be wastes.
• Think about preparing a meal; there will be vegetable peelings and fruit cores, there may be
skin and fat trimmed off fish and meat, and, if canned or bottled ingredients are used, there
will be the empty bottles and cans.
• Households, businesses, industries, the healthcare system and public organizations all
produce wastes that need to be processed.
• We will learn how the waste hierarchy can be applied to help reduce, reuse or recycle the
solid wastes that we produce.

Waste reduction
• At the top of the hierarchy is waste reduction. This is the best option because the most
effective way to limit the health effects and environmental impacts of a waste is not to
create waste in the first place.
• Making any new product requires materials and energy.
• Raw materials must be extracted from the Earth and processed, and the product must be
manufactured, packaged and transported to wherever it will be sold.
• Each of these stages may produce solid waste as well as liquid wastes and air
pollutants. If we can find ways of making a particular item whilst producing less waste
in the process, this is one of the most effective ways to reduce pollution, save natural
resources, protect the environment and save money.
• Industry has a major part to play in waste reduction.
• If more efficient manufacturing processes were adopted, greater quantities of products
could be made without increasing the use of raw materials.
• Industry can also work to incorporate less material into its products – so for example,
an item could be packaged using less cardboard than before.

• Waste reduction is also important at household level.
• In Ethiopia a number of waste reduction initiatives have been put in place in big
cities like Addis Ababa and Mekelle by informal organizations and private sector
enterprises. These initiatives frequently involve several different stakeholder groups
including urban Health Extension Workers (HEWs), civil society, private sector
enterprises and organised women’s development groups.
• The local kebele administration and appropriate experts from the Woreda Health
Office and Greenery and Beautification Office are also likely to be involved.

• The Ministry of Health has produced some teaching aids and promotional materials
aimed at educating communities on how to reduce and minimise waste at household
level. Educational campaigns can raise awareness of the individual economic
incentives and can also be used to reduce the stigma attached to working with waste.
• Part of your role as an urban WASH (WASH is an acronym that stands for "water,
sanitation and hygiene ) worker may be to help educate householders, through
home visits and at community gatherings, about better ways to manage their domestic
waste. This can result in behavioral change among the community members and
increase their active participation in waste reduction (and reuse) at the household
level.

There are many possible ways of reducing the amount
of waste produced at home that could be suggested to
householders.
• These include educating and encouraging them to:
• Buy products that use less packaging. Buying in bulk, for example, can reduce
packaging and save money. Where households cannot afford to pay large sums of money
up front, it may be possible for neighbors to club together and buy a large quantity of a
basic foodstuff between them.
• Make use of reusable rather than disposable items. For example, use refillable containers
where possible; washable rather than disposable nappies; cotton handkerchiefs rather
than paper tissues; rechargeable batteries and refillable ink pens.
• Use their own shopping bags, preferably made of cloth or other recycled material rather
than plastic bags.
• Minimize food scraps or feed these scraps to animals, if appropriate.
• Repair and maintain items such as clothing so that they last longer.

Waste reuse
• Reuse can be defined as using a waste product without further transformation
and without changing its shape or original nature. This is the second option in
the waste hierarchy. Different types of solid wastes can be reused, such as
bottles, old clothes, books and anything else that is used again for a similar
purpose to that originally intended. Reuse means that less solid waste is
produced. It brings other benefits by taking useful products discarded by those
who no longer want them and passing them to those who do.

• The informal waste management sector does a lot to promote reuse and
recycling. Individuals (known as korales) buy reusable bottles and jars
and recyclable materials from householders and sell them on to small
shopkeepers and merchants. Bjerkli (2005) estimated that around 5000
korales were working in Addis Ababa.

Figure 8.2 Collecting and selling reusable plastic bottles.

Benefits of reducing and reusing solid waste
• Waste is becoming a bigger problem in urban areas each year. Households are
producing more waste, so disposal sites are filling up and new sites are further
away from residential areas. Where waste is collected and transported to a
disposal site, this is becoming more expensive. Where householders have to
dispose of waste themselves, they have to spend more time doing this. Anything
that reduces the amount of waste that has to be disposed of helps to reduce these
problems.
• Some other advantages of waste reduction and reuse are summarized below.
• Community benefits
• Reuse can be very helpful for people who cannot afford to buy new goods. These
could include clothing, building materials, and business equipment. Reuse
centers that collect and distribute reusable goods can also provide community
benefits by engaging in job-training programs and general training for the long-
term unemployed, disabled people and young people.

• Economic benefits
• By reusing materials rather than creating new products from raw materials, there
are fewer burdens on the economy as a whole – especially if reuse results in a
reduction in raw material and product imports. Reuse is an economical way for
many people to acquire the items they need. It is almost always less expensive to
buy a used item than a new one.
• Environmental benefits
• Reusing something uses little or no water, energy or other resources and is
unlikely to cause pollution. As well as these benefits, reuse eliminates the
environmental damage that would have been caused if the item had been
disposed of, rather than reused. In contrast, manufacturing a product from raw
materials (and, to a lesser extent, recycling) consumes resources, causes
pollution and generates wastes.

Waste recycling
• Recycling waste means that the material is reprocessed before being used to make
new products. The reprocessing activities can have an impact on people’s health and
the environment, but these impacts are usually lower than those from making the
product from new, raw materials. Recycling means treating the materials as valuable
resources rather than as waste. It has many benefits but it is important to have a
market for the end product, otherwise the process will not be economically
sustainable.
• The options for recycling depend on the type of waste. For example, waste paper can
be broken down to its fibres in a process called pulping. The pulp is cleaned and then
formed into new paper to be used for printing or packaging. Waste metals and glass
can also be recycled by melting them down into new raw materials. Sheet metals can
be beaten and reformed into new products (Figure 8.3). Plastic bottles can be ground
down and used to make plastic rope or plastic coating for electric wires. For some
wastes, recycling involves complex technical processes and requires specialized
machinery, but others can be recycled more simply and on a small scale. All types of
organic waste can be recycled by composting, which can be carried out at home or on
a larger scale.

Figure 8.3 Large metal containers can be cut and reformed into
new products like these sieves and stoves.

Waste separation
• It is difficult to recycle materials once different wastes have been mixed together,
so the first stage of the recycling process is to separate the materials into different
categories. This is called waste segregation or separation at source and should be
done by the householder when the waste items are finished with and discarded.
Waste is separated by placing the different categories of waste into different bags
or containers.
• The degree of separation required will depend on the recycling opportunities that
are available, but it is important to separate ‘dry’ and ‘wet’ materials. The simplest
method of separation is to keep food waste separate from the remaining materials
so that the food waste can be composted or used to make biogas. If korales are
active in the area, they may ask householders to keep all their recyclable materials
(paper, metals, plastics and glass) together, or ask for just one or two materials to
be separated.

• If waste is not separated at the source, it ends up at a disposal site where all the waste is
mixed up so separating the different types becomes much more difficult and hazardous.
• In many developing countries, including Ethiopia, collecting waste for recycling is often
conducted by the informal sector.
• Such work can be done in a very labour-intensive, unsafe and polluting way, and for very
low income. Often young children are employed as collectors.
• Part of a WASH team’s job is to help put the recycling industry on a more formal basis.
This is another aspect of waste management that requires collaboration among
stakeholders, including the informal sector and other concerned partners, to help improve
the working conditions and provide protective equipment and training to the korales and
other waste collectors.

• It is possible to set up a more formal scheme to collect recyclable materials
where the collectors provide separate receptacles (containers) for recyclable and
non-recyclable wastes. Although separation has the advantage of promoting
recycling, it also has the disadvantages of higher collection costs and needing
special equipment and additional workers to collect each type of material.
Therefore, in most urban and peri-urban areas, recycling collections are carried
out by the informal sector.
• Once separated materials have been collected from householders by the korales
or by the more formal sector, they are passed on to merchants and eventually to
the industrial operations that transform the wastes back into useful raw materials
or products. Much of this part of the recycling chain falls outside the work of a
local WASH team, but team members can still help people to become more
aware of the importance of waste recycling and encourage them to separate
materials for collection.

Composting
• Composting is the process where biodegradable organic wastes (food and
garden waste) are converted into compost in a natural biological process.
Composting can be done by individual householders and community groups or
on a commercial scale.
• On the larger scale, the waste from an entire town or city could be composted if
sufficient land, labour and equipment is available. The benefits of composting
are not only the reduction of waste, but also the production of compost which is
a valuable soil improver.
• Soils treated with compost are better able to withstand droughts and are more
fertile because plant nutrients are returned to the soil, which reduces the need
for manufactured fertilizers.
• It is possible to add a certain amount of animal manure to residential waste for
composting, which may help with other waste problems in the community and
adds to the amount of useful soil improver that is made.

The composting process.
As an urban WASH worker you may be required to help individuals or communities set up and operate composting processes. The stages in the composting process are ou

1.Separation of compostable materials: It is important to begin with an uncontaminated input to
the process. Nearly all organic wastes can be composted, but if a composting pile attracts
rodents and other scavenging animals it may be better to exclude meat products and cooked
food from the process and just collect garden waste and raw vegetable waste.
2.Grinding or shredding: To speed up the composting process it may be necessary to shred the
raw waste before placing it in the compost pile. Shredding is normally required if a significant
proportion of the waste has particles greater than about 50 mm. On a domestic scale this can be
achieved simply by cutting up the waste into smaller pieces.
3.Blending or proportioning of materials: Composting works best with the right mixture of wastes
so that the moisture content and the proportions of the chemical elements carbon and nitrogen
are suitable. Generally, the ideal mix for composting is three parts (buckets, for example) of
‘brown’ waste (such as leaves, hay, straw, eggshells, shredded paper, card and woody material),
with one part ‘green’ material (such as grass, food waste and animal manure). ‘Brown’ waste
contains a higher proportion of carbon and ‘green’ waste, contains more nitrogen and has a
higher moisture content. Thus the ratio of brown waste to green waste is 3:1.
4.Composting: Composting is normally carried out in a pile. For larger scale composting
processes, piles are in the shape of long rows of waste, normally with a triangular cross-section.
The ideal pile is 1.5–2 m wide and about 1.5 m high. The length of the pile is determined by the
space and the amount of waste available. On the domestic scale the pile will be much smaller,
forming a rounded heap. The pile can be built up as waste becomes available, but it is important
to have enough material present to allow the biological processes to take place reasonably
quickly, so as a guide a domestic compost heap should be at least 1 cubic metre to start the
process.

Composting process: mixed waste is piled in long rows.

• Composting is an aerobic process, so the pile needs to be turned regularly to
introduce air. This means dismantling (breaking) it, mixing the waste to
introduce air and then rebuilding the pile. The first turning-over of the heap
should be done after two to three weeks and then every three weeks or so. The
composting process will be complete within three to six months. The
composting process generates heat, so it is normal to see steam coming out of
the pile.
• The process is complete once the pile no longer heats up after mixing and
rebuilding. The final product should be brown and crumbly (powdery) and
look like a good soil. If it still contains identifiable items, the process is not
complete.

Energy recovery
• The fourth option in the waste hierarchy is recovery. Recovery is about finding
other uses for wastes that enable some value to be extracted or recovered from
them, usually by using them as a source of energy.
• Recovering energy from waste on a large scale using an advanced incineration
plant is a high-technology, high-cost option that is common in many developed
countries. However, it needs a highly developed infrastructure (a reliable source
of waste, good roads, a reliable waste collection service, a power distribution
grid, etc.) and large amounts of waste. This technology is currently rarely used
in low- and middle-income countries, but as cities develop there is great
potential for energy-from-waste in the future in Ethiopia and many other
countries (Scarlat et al., 2015).

Biogas production
• This technology can be used to treat food waste on its own or in combination
with human excreta or animal manure.
• Biogas recovery from organic waste can be done at the kebele or household
scale, where the biogas can be used for cooking and heating water. The sludge
from the digester can be used as a fertiliser and soil improver. Another benefit
of biogas production is the reduced use of fuel wood, which improves living
conditions by reducing indoor air pollution. Additionally, biogas contributes to
the reduction of greenhouse gases. The use of biogas as a cooking fuel will
mainly benefit women because it will reduce their overall workload by
providing energy for the household without requiring labour-intensive fuel
collection.

Figure 8.6 A biogas instructional poster from the Biogas Pilot Program (BPP).
Biogas production needs more equipment than composting, so it is more expensive to
install. It also requires greater expertise than composting to operate and the
equipment must be maintained. Small-scale biogas is well established in China and
India, but this method is still relatively uncommon in Ethiopia (Rajendran et al.,
2012).

Waste-to-energy (Municipal Solid Waste)

How waste-to-energy plants work
• Waste-to-energy plants burn municipal solid waste (MSW), often called
garbage or trash, to produce steam in a boiler that is used to generate
electricity.
• MSW is a mixture of energy-rich materials such as paper, plastics, yard
waste, and products made from wood. For every 100 pounds of MSW in the
United States, about 85 pounds can be burned as fuel to generate electricity.
Waste-to-energy plants reduce 2,000 pounds of garbage to ash weighing
about 300 pounds to 600 pounds, and they reduce the volume of waste by
about 87%.
• There are different types of waste-to-energy systems or technologies. The
most common type used in the United States is the mass-burn system, where
unprocessed MSW is burned in a large incinerator with a boiler and a
generator for producing electricity (see illustration below). Another less
common type of system processes MSW to remove most of uncombustible
materials to produce refuse-derived fuel (RDF).

A mass-burn waste-to-energy plant

The process of generating electricity in a
mass-burn waste-to-energy plant has seven
stages:
1.Waste is dumped from garbage trucks into a large pit.
2.A giant claw on a crane grabs waste and dumps it in a combustion
chamber.
3.The waste (fuel) is burned, releasing heat.
4.The heat turns water into steam in a boiler.
5.The high-pressure steam turns the blades of a turbine generator to
produce electricity.
6.An air pollution control system removes pollutants from the combustion
gas before it is released through a smoke stack.
7.Ash is collected from the boiler and the air pollution control system.

INCINERATION
• Is a process in which MSW is burnt under suitable temperature for
specific period of time in a designed furnace
• It is a chemical process
• Reduces the weight & Volume considerably
• Weight is reduced by 75 % & Volume by 95 %
• It requires high energy
• It increases the cost of MSW management
• It also requires highly skilled personals

INCINERATION
Oxidation: MSW burns in presence of oxygen. As
a result of oxidation process water and CO2 is
formed. The process is called oxidation.
For complete Oxidation Process, sufficient
amount of air is mixed with MSW

• Temp. of a typical furnace 815 °C or (1500 ° F)
• For some other Furnaces, temp. may rise to 1400 °C
or (2550 °F)
Resource Recovery:
It is a system where heat energy produced during the
incineration process is used for production of steam
or elecricity

Incinerator Residues & Emissions
• Bottom Ash:
• it is solid residue of MSW incineration. Its volume
is usually 5% of total MSW volume.
• Fly Ash:
• It is very small and finer particles of ash matter
which are carried along with combustion air
stream.
• It contains very small particles like mineral dust
etc
• It may contain a good concentration of heavy
metals like lead & cadmium

•TEST:
•a test is carried out at incineration
plants to determine whether the
bottom ash or fly ash may be
treated as hazardous waste?
•Treatment of Ash:
• Fly ash or residual ash may be
treated with water or lime. This will
form cement like hard substance
and heavy metals are immobilized.

Use of Air Pollution Control Systems
Location: Air Pollution control systems are located after the
incinerator and before the chimney/stalk e.g Fabric filters, acid gas
scrubbers & electrostatic precipitators
Height of Chimney/Stalk:
Ranges between 6o m – 180 m
The height of chimney helps in dilution of pollutants

Factors affecting Air Pollution Control Systems
• Temperature of Incinerators
• Burning time of MSW
• Composition of MSW
• Sufficient air supply during the incineration process

Design & Operation of Incinerators
• Cont-Feed-operation: There is always a cont. supply of refuse which
allows for uniform furnace temperature
• Batch Feed Operations: It is an intermittent feed operation

Design of a Typical Incinerator
• Refuse Storage Pit/tipping Area:
• it provides volume of MSW for at least one
day
• Refuse is lifted with crane with grub bucket,
deposited into charging hopper and chute
• Then it is released from chute onto a
charging grate or stoker
• Various types of mechanical grates are
available to agitate and allow the burning
material through furnace

Phases of Combustion in a furnace
• Two phases
• Primary Combustion
• Secondary Combustion
• Primary Combustion:
• Moisture is driven off, burnable waste is volatized and
ignited
• Secondary Combustion:
• Remaining unburned gasses and particulates are
entertained in air stream after primary combustion by
oxidation process.
• It eliminates odors and unburned particulates in
exhaust air

•The furnaces of incinerators that are
not used for energy recovery are
typically built with refractory materials
which resist the effects of very high
combustion temperatures.
•Refractroy bricks are made up of
aluminia, magnesia, silica and kaolin
•Thickness of refractory walls is 225 mm
(9 inches)

Energy Recovery
•Recovery of heat given off by burning
refuse in an incinerator is accomplished
by refractory lines furnace followed by a
boiler.
•The boiler converts the from combustion
into steam or hot water
•Energy component of refuse can be
recycles and put into beneficial use

• Water Tube Walled Furnace:
• It is lined with closely spaced welded steel tubes
arranged vertically to form continuous walls
• Insulation on the outside walls reduces the heat
loss
• Heat is absorbed by water and it circulated
through the tubes, this heated water is used to
produce steam
• An advantage to this type of system is that water
is also used to control the temperature of the
furnace

•MASS BURNING:
•When unprocessed solid waste is used as a
fuel directly into a heat recovery type of
facility, the process is referred to as “mass
burning”
•Refuse Derived Fuel:
•When the refuse is fed after processing i.e.
by shredding or by separation of non-
combustible waste materials before being
fed to the incinerator, the MWS is called
Refuse Derived Fuel or RDF.

Important Features of Energy Recovery System
•It is an attractive option for MSW
management with environmental and
ecological perspective
•It is very costly to install and operate
•It is comparatively very attractive
option as compared to land fill

Pyrolysis
•It is a high temperature thermal
process that can provide an
alternative to incineration
•It needs low or no oxygen and
produces by products that can be
used as fuels
•Natural gas is required to start
process of Pyrolysis

•Instead of Oxidation a complex
series of decomposition and other
chemical reactions take place
•It can be used for processing of
rubber tyres
•Rubber is reduced to oil and
methane gas which can be sold

COMPOSTING
• Is a process in which organic portion of MSW is allowed to
decompose under carefully controlled conditions.
• It is a biological process
• Decomposition of organic matter is achieved by a combine
activity of bacteria, viruses, fungus and other organisms
• By controlling temp. moisture and air, a compost plant can
reduce the size of MSW as much as 50 % of the actual size
of MSW

PROCEDURES OF COMPOSTING
It includes;
• Sorting
• Separating
• Shredding
• Pulverizing
• Digestion
• Product up-grading
• marketing

•Sorting & Separating;
•It includes isolating organic and
decomposable material from metals,
plastics, glass and other non-degradable
wastes
•Shredding & Pulverizing:
•Add to reduce the size of MSW
•Result in relatively uniform mass of matter
•Helps in optimizing bacterial activity and
increasing the rate of decomposition
PROCEDURES OF COMPOSTING

Digestion by using open wind rows
•A wind row is a long, low pile of
the prepared organic waste,
usually about 3 m wide at base and
about 2 m high
•Windrows are conical in cross
section and about 50 m in length
•Composting waste is aerated by
periodic turnings

•Turnings can be done manually by
pitch fork or by specially designed
machinery
•Open field windrow composting 5
weeks for digestion or stabilization
of waste material
•An additional 3 weeks may be
required some times to ensure
complete stabilization

•Tem. In aerobic windrow may
reach 65°C because of natural
metabolic action of thermo-
phylic bacteria
•Relatively high temp. may
destroy most of pathogens
•Open field windrow requires
large land areas

Digestion in closed vessels
•It may reduce the required time to 1
week
•The closed vessels or tanks may be
equipped with rotating plows etc for
mixing
•In some systems compressed air is
blown into the vessel for aeration

Marketing of Compost
Before marketing one may upgrade the quality
and appearance of compost by;
•Drying
•Screening
•Granulating or pelletizing
•Compost can increase the nutrient content of
the soil and improving texture and porosity of
soil.

Co-composting
•Co-composting is adding of sewerage
sludge with organic wastes of MSW
•Sewerage sludge adds nitrogen,
phosphorus and other trace elements
•Sludge is first de-watered
•De-watered sludge is thoroughly mixed
with the MSW

Static Aeration Method
•When sludge is co-composted with the MSW,
Static aeration method or mechanical agitator
method is used
•In this method, compressed air is either forced
up through composting waste or pulled down
through it
•A perforated pipe about 6 inches in diameter is
located under the windrow
•Air is forced in or out for 5 minutes at 15
minutes interval

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