What is Solid Waste?
Combustion (preferably with energy
recovery)
Solid waste means any garbage, refuse,
sludge from a wastewater treatment plant, Land filling
water supply treatment plant, or air pollution
Kinds of Waste
control facility and other discarded materials
including solid, liquid, semi-solid, or contained Solid wastes: wastes in solid forms, domestic,
gaseous material, resulting from industrial, commercial and industrial wastes Examples:
commercial, mining and agricultural plastics, bottles, cans, papers, scrap iron, and
operations, and from community activities. other trash
In 1989, the U.S. Environmental Liquid Wastes: wastes in liquid form Examples:
Protection Agency (U.S. EPA). Adopted a domestic washings, chemicals, oils, waste
hierarchy of wastes management practice to water from ponds, manufacturing industries
be used as a guideline by communities when and other sources.
they prepare waste management plans (U.S.
Bio-degradable: can be degraded (paper,
EPA 1989). The four elements of the hierarchy,
wood, fruits and others)
in order of preference, are:
Non-biodegradable: cannot be degraded
Source reduction (including reuse of
(plastics, bottles, old machines, cans,
products and backyard composting of
Styrofoam containers and others)
yard wastes).
Hazardous wastes: Substances unsafe to use
Recycling of materials
commercially, industrially, agriculturally, or
economically and have any of the following
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properties- ignitability, corrosively, reactivity & 4. Biodegradable material: any organic
toxicity. material that can be broken down by
microorganisms into simpler, more
Non-hazardous: Substances safe to use
stable com-pounds. Most organic wastes
commercially, industrially, agriculturally, or
(e.g., food, paper) are biodegradable.
economically and do not have any of those
properties mentioned above. These 5. Compost: the material resulting from
substances usually create disposal problems. com posting. Compost, also called
humus, is a soil conditioner and in some
instances is used as a fertilizer.
Basic terms related to solid waste
6. Composting: biological decomposition
1. Ash: the non-combustible solid by-
of solid organic materials by bacteria,
products of incineration or other burning
process. fungi, and other organisms into a soil-like
product.
2. Bulky waste: large wastes such as
appliances, furniture, and trees and 7. Disposal: the final handling of solid
branches, that cannot be handled by waste, following collection, processing,
normal MSW processing methods. or incineration. Disposal most often
3. Co-disposal: the disposal of different means placement of wastes in a dump or
types of waste in one area of a landfill or a landfill.
dump. For instance, sewage sludge's may
be disposed of with regular solid wastes.
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8. Environmental impact assessment (EIA): 11. Land filling: the final disposal of
an evaluation designed to identify and solid waste by placing it in a controlled
predict the impact of an action or a fashion in a place intended to be
project on the environment and human permanent. The Source Book uses this
health and well-being. Can include risk term for both controlled dumps and
assessment as a component, along with sanitary landfills.
economic and land use assessment.
12. Leachate: liquid that has seeped
9. Environmental risk assessment (ERA): an through a landfill or a compost pile and
evaluation of the interactions of agents, has accumulated bacteria and other
humans, and ecological resources. possibly harmful dissolved or suspended
Comprised of human health risk materials.
assessment and ecological risk
13. MSW: municipal solid waste.
assessment, typically evaluating the
probabilities and magnitudes of harm 14. MSWM: municipal solid waste
that could come from environmental management.
contaminants. 15. Putrescible: subject to
10. Garbage: in everyday usage, refuse decomposition or decay. Usually used in
in general. Some MSWM manuals use reference to food wastes and other
garbage to mean "food wastes," organic wastes that decay quickly.
although this usage is not common.
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16. Refuse: all kinds of wastes in solid various industries like chemical,
state excepting excreta from residential, petroleum, coal, metal gas, sanitary &
commercial and industrial area. paper etc.
Agricultural wastes: Wastes generated
from farming activities. These
Classification of wastes according substances are mostly biodegradable.
to their origin and type
Fishery wastes: Wastes generated due to
Municipal Solid wastes: Solid wastes fishery activities.
that include household garbage, rubbish,
E-wastes: Electronic wastes generated
construction & packaging materials,
from any modern establishments. They
trade refuges etc. are managed by any
may be described as discarded electrical
municipality.
or electronic devices. Some electronic
Bio-medical wastes: Solid or liquid scrap components, such as CRTs, wires,
wastes including containers, products circuits, mobile, computers etc.
generated during diagnosis, treatment &
research activities of medical sciences.
Industrial wastes: Liquid and solid
wastes that are generated by
manufacturing & processing units of
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Municipal Solid Waste Changes in MSW
MSWotherwise known as trash or Urbanization, (i.e., the flux of people to
garbageconsists of everyday items metropolitan areas) affects living habits
such as product packaging, grass and consequently waste characteristics.
clippings, furniture, clothing, bottles, Also, with more people, the areas
food scraps, newspapers, appliances, and requiring solid waste collection have
batteries. Not included are materials that expanded and site for waste disposal are
also may be disposed in landfills but are farther away.
not generally considered MSW, such as
Industrialization, because it generates
construction and demolition materials,
inexpensive, laborsaving products, has
municipal wastewater treatment
created a throwaway society. During
sludge's, and non-hazardous industrial
1960 and 1970, new products appeared
wastes.
in abundance. Cans, bottles, plastic
The two root cause for the increasing containers, appliances, tires, and many
urgency of solid waste problems are other items were considered to be
urbanization and industrialization. cheaper to throw away than reclaim.
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Example:
In 1920, five trucks were required to collect
5800 tones (6400 tons) per year of residential
and commercial waste from the municipality
of 20,000 people. By 2000, when the
population is expected to reach 100,000:
a) How would the annual quantity of
refuse collected have changed if
special wastes were not included in the
annual amounts?
b) Neglecting lost time because of vehicle
breakdown and maintenance, how many
trucks of 4.5 tones (5 tons) capacity,
operating 5 days per week, would be
required for twice-weekly collection if
trucks averaged 2 loads/day at 80%
capacity?
c) How did the quantity of paper change
during the 80-years period?
Figure 1
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collected may be less than that
generated. In this chapter, differences
between the quantities generated and
collected are ignored because variations
due to other factors are much more
significant.
Quantities Characteristics
In wet areas, because of moisture Composition. In addition to the variation
absorbed by the solid waste, the amount in quantity, wide differences in waste
collected may exceed the amount composition can also occur. Factor
generated, which is usually reported on a influencing the composition of MSW
dry basis. On the other hand, with the include such things as:
use of home grinders, on-site storage of
recyclable materials, and other
conservation measures, the amount
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Climate. In wet areas such as Sao Paulo, wide use of packaging has increased the
Brazil, the moisture content of solid paper content of solid waste.
waste is typically 50%
Degree of urbanization and
Frequency of collection. More frequent industrialization of the area. Because of
collection tend to increase the annual the composting, recycling, and recovery
amount collected. Since the amount of possible in rural areas and areas with
organics is relatively constant, perhaps single-family dwellings, solid wastes from
with more pickups there is a tendency such sources may be less in quantity and
for residents to discard more paper and of different constituents than that from
rubbish. industrialized metropolitan areas with
multiple-family housing.
Prevalence of home garbage grinders.
Grinders reduce, but do not eliminate,
food wastes.
Social customs. Some ethnic areas use
few convenience foods, so less paper and
more raw food waste result.
Per capita income. Low-income areas
produce less total waste but with higher
food content.
Acceptability of packaged and
convenience foods. In north America,
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Density. The density of municipality solid
waste varies with waste composition and
the degree of compaction. Typical values,
shown in Figure 14-2, range from an
compacted density of 150 3 to 800 3
for landfilled, pulverized refuse. Un
compacted densities for the various
components (as collected are noted in
Table 14-4.
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each 14,100 kJ/kg. The energy content
shown for each material is its heat of
combustion. In comparing solid waste
with other fuels, the energy required for
shredding and classification of the refuse
should be considered, as should the
difference in operating efficiency
between the incinerator and other type
of furnace
Energy content. Municipal solid waste
contains about 50% volatile
(combustible) matter, the balance being
roughly equal proportions of moisture
and inert solids. Because of the volatile
content, the waste is often burned as a
means of disposal and occasionally
utilized as a source of energy. Table 14-5
indicates typical energy contents for
various combustible materials, including
un-compacted solid waste, which may
have an energy content from 9300 to for
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consisting of 50% paper and 20% metal, glass,
and ash, with the balance being food and
other organic wastes.
Solution:
An outline of the procedure for estimating the
energy content of solid waste is given in the
following table
Consideration in S0lid Waste
Example:
Management
Base on the energy content of the
components of MSW as collected (table 14-5), As with every engineering decision,
determine the energy content in refuse economic considerations are a major concern
in solid waste management. However, the
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protection of public health and environmental
Compaction of waste to at least 600
3
conservation must not be neglected
(1000 ) to reduce insect breeding
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place and rodent access
Protection of Public Health and the Processing within 2 days (since fly larvae
become flies in a few days)
Environment
Shredding of waste to promote aerobic
Under warm, moist conditions,, organic decomposition, which is a heat-
waste become ideal breeding places for producing process and therefore
disease-causing organisms. Pathogens, even if unattractive to insects and vermin
absent initially, have easy access to the waste
The generation of harmful organisms and
via vectors. With solid wastes, the usual
vectors (carriers) for disease transmission (i.e., their transmission is not the only health
water, air, and food) are not important; flies, related concern. Many potentially harmful
rodents, and mosquitoes are the primary materials, such as solvent and pesticide
vectors. The major diseases of concern containers, medical wastes, and asbestos
associated with flies and mosquitoes are debris, even though prohibited, may already
gastroenteritis, dysentery, hepatitis, and
be present in the waste when it is collected.
encephalitis (Pfeffer, 1992). Wilson (1977) has
suggested the following measures to reduce
vermin-related health hazards:
The use of tightly closed containers for
organic waste
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Source Reduction 2. The passing of laws that minimize the
use of virgin materials in consumer
Source reduction, define as a reduction in the products
amount and/or toxicity of waste entering the
waste stream, is distinguished from recycling, 3. The adoption by communities of rate for
composting, and other recovery practices, waste management services that
which all occur after generation of the waste. penalize generators for increasing waste
Source reduction is the highest ranking quantities
component of the solid waste management
hierarchy because it represents the most
effective means of reducing the economic cost Recycling
and environmental impacts associated with After source reduction, recycling is the most
handling waste. important practice within the solid waste
Three key requirements for management hierarchy. However, over the
past 250 years, the proportion of domestic
implementing a source reduction
waste that has been recycled has declined
program: steadily from over 90% to about 7% in 1970.
1. The adoption of industry standards for since then, interest in recycling has been
product manufacturing and packaging revived, and in 1987 New Jersey passed the
using less material first state wide mandatory recycling
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legislation. Under this law, residence in the capacity, and the cost of composition
states 567 communities were required by due to processing during recovery mean
1989 to recycle 25% of the solid waste that these materials are usually inferior
generated and all towns were required to in quality and thus lower priced than
compost leaves. virgin materials
Aluminum Recycling. Due to the high cost
of imported aluminum ore (bauxite) and
Markets for Recycled Materials the development of an extensive
A successful recycling program requires collection processing infrastructure,
the existence of a reliable nearby market aluminum is the most successful recycled
for the recovered materials. Although commodity
the recovery of certain materials such as Paper and Cardboard Recycling. Although
aluminum cans and large plastic bottles paper and cardboard combined
can be profitable, this is not the case for represent the largest category of MSW
most other recycling programs, which efforts to recycled the various type of
must be subsidized and/or legislated by paper have met only limited success. This
government. has been attributed to three factors
Market development will depend on the
quality of the materials, overall industry
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1. The abundance of relativity cheap materials, compacted, and detained prior
virgin fiber in the United States and to reuse.
Canada
2. The long distances between many
urban centers and the processing mills
Recovery of Energy
3. Limited mill capacity to deink and The two principal ways to use the energy
reuse post consumer paper contained in municipal solid wastes are (1) to
Glass Recycling. Because recycled use the material as fuel and (2) to recover
crushed glass melts at a lower material for reuse, thus saving the energy
temperature that the raw materials used needed for processing and transporting virgin
in glass production. material.
Plastic Recycling. The production of
plastic has increased dramatically in the Fuels from solid wastes
past 20 years, due primarily to its Solid waste may be burned directly in
increased use in packaging and as incinerators (a process called mass-burning) or
container material. converted to more efficient refuse-derived
Ferrous metal recycling. Tin cans, the fuel (RDF). The controlled burning of either
major category of recycled ferrous metal, municipal solid waste or RDF can produce hot
must be separated from non-ferrous water or steam for heating, or steam for
driving turbines to generate power.
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