Chapter 17 - HCC Learning Web

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Environmental Science
A Study of Interrelationships
Twelfth Edition
Enger & Smith
Chapter 17
Solid Waste Management and Disposal
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Solid Waste Management and Disposal
Outline
 Kinds of Solid Waste
 Municipal Solid Waste
 Methods of Waste Disposal
Kinds of Solid Waste
 Solid waste is generally made of objects or
particles that accumulate on the site where they
are produced.
• They are typically categorized by the sector of the
economy responsible for producing them.
Kinds of Solid Waste
 Mining wastes are generated in three ways:
• Waste material is left on the surface
• Milling tailings are dumped on the land or stored in
ponds.
• Waste or tailings drainage often contains hazardous
materials.
 Agricultural waste
• Includes waste from raising animals as well as crop
and tree harvesting.
– 90% is used as fertilizer or other forms of soil
enhancement.
Kinds of Solid Waste
 Industrial solid waste consists of solid waste other
than mining.
• Estimated to be between 200-600 million metric tons
annually.
– Demolition waste
– Sludge
– Combustion ash
 Municipal solid waste consists of all the materials
people in a region no longer want.
– 210 million metric tons annually.
Municipal Solid Waste
 In modern society, many products are discarded
when they are broken or worn out, while others
only have a temporary use.
 Those that have only temporary uses make up
the majority of solid waste.
Municipal Solid Waste
 The Unites States produces about 210 million metric
tons of municipal solid waste annually.
• This equates to 2 kg (4.4 lbs) of trash per person per day.
– Per capita waste has increased 70% since 1960.
Municipal Solid Waste
Municipal solid waste generation rates
Municipal Solid Waste
 Nations with a higher standard of living tend to
produce more municipal solid waste per person
than less-developed countries.
 Large metropolitan areas have the greatest
difficulty dealing with solid waste.
Municipal Solid Waste
Waste generation and lifestyle
Methods of Waste Disposal
 In the past, the favored means of waste disposal
was to dump solid wastes outside of city or
village limits.
 To minimize the volume of waste, the dump was
often burned.
 This practice is still employed in remote or
sparsely populated areas in the world.
Methods of Waste Disposal
 Five techniques are now used in waste disposal:
•
•
•
•
•
Landfills
Incineration
Source reduction
Composting
Recycling
Methods of Waste Disposal
 Landfills
• A municipal solid waste landfill is typically constructed
above an impermeable clay layer, lined with an
impermeable membrane.
• It includes mechanisms for dealing with liquid and gas
materials generated by the contents of the landfill.
• Traditionally this has been the primary method of waste
disposal.
– Cheap and convenient
• Problems associated with poorly designed landfills have
been recognized, and substantial efforts are made to
reduce the amount of waste entering landfills.
Methods of Waste Disposal
 New landfills have complex bottom layers to trap
contaminant-laden leachate.
 Monitoring systems are necessary to detect
methane gas production and groundwater
contamination.
 In some cases, methane is collected and used to
generate electricity.
 New landfills currently cost up to $1 million per
hectare to prepare.
Methods of Waste Disposal
A well-designed modern landfill
Methods of Waste Disposal
 The number of landfills is declining.
• Many small landfills that were not meeting regulations
have been closed.
• Capacity has been reached.
 New landfills often resisted due to public concerns
over groundwater contamination, odors, rodents,
and truck traffic.
• Politicians are often unwilling to take strong positions
that might alienate constituents.
Methods of Waste Disposal
Reducing the number of landfills
Methods of Waste Disposal
 Incineration is the process of burning refuse in a
controlled manner.
 Currently, about 15% of U.S. municipal solid waste
is incinerated.
• Most incinerators are designed to capture heat, which is
then used to make steam to produce electricity.
• The production of electricity partially offsets disposal
costs.
• Most incinerators burn unprocessed municipal solid
waste. This process is referred to as mass burn
technology.
Methods of Waste Disposal
 Incinerators drastically reduce the amount of
municipal solid waste.
• Up to 90% by volume and 75% by weight.
 Primary risks of incineration involve air quality
problems and toxicity and disposal of ash.
• Toxic substances are more concentrated in ash.
Methods of Waste Disposal
 Even with modern pollution controls, small
amounts of pollutants are still released into
environment.
 The cost of land and construction for new
incinerators are also major concerns facing
many communities.
 Construction costs in North America in 2000
ranged from $45-$350 million.
Methods of Waste Disposal
 U.S. EPA has not looked favorably on
construction of new waste-to-energy facilities.
 It has encouraged recycling and source
reduction as more effective solutions to deal with
solid waste.
Methods of Waste Disposal
Disposal methods used in various countries
Methods of Waste Disposal
 Mulch is organic material used to protect areas
where the soil is disturbed, or to control growth
of unwanted vegetation.
 Organic materials such as large branches and
bark are chopped or shredded into smaller
pieces.
Methods of Waste Disposal
 Composting is using natural decomposition to
transform organic material into compost, a
humus-like product with many environmental
benefits.
• With proper management of air and water,
composting can transform large quantities of organic
material into compost over a short period of time.
• Small-scale composting can be accomplished in the
backyard, mixing green materials (grass clippings,
vegetable scraps, etc.) and brown materials (dry
leaves, twigs, soiled paper towels).
Methods of Waste Disposal
Diverting waste through composting
Methods of Waste Disposal
 About 3,800 composting facilities are currently in
use in the United States.
 Most municipal programs involve one of three
composting methods:
• Windrow systems
• Aerated piles
• Enclosed vessels
Methods of Waste Disposal
 The simplest way to reduce waste is to prevent it
from ever becoming waste in the first place.
 Source reduction is the practice of designing,
manufacturing, purchasing, using and reusing
materials so that the amount of waste or its toxicity
is reduced.
Methods of Waste Disposal
 Design changes
• Since the 2-liter soft drink bottle was introduced in 1977,
weight has been reduced by 25%.
• As a result, 250 million pounds of plastic have been
kept out of the waste stream.
 Manufacturing processes reduce waste and
increase efficiency.
 Purchasing decisions
• Choose reduced packaging and plan quantities
accordingly.
Methods of Waste Disposal
 Using materials to avoid waste generation
• Reduce use of hazardous materials.
• Follow label directions carefully and use the smallest
amount necessary.
 Reusing items
• Delay or prevent entry of items into waste collection
stream.
Methods of Waste Disposal
 Most businesses and manufacturers have a strong
economic incentive to ensure they get the most
from all materials they use.
• Any activities that reduce the amount of waste
produced, reduce the:
– Cost of waste disposal
– Amount of raw materials needed
– Amount of pollution generated
Methods of Waste Disposal
 Recycling is one of the best environmental
success stories of the late 20th century.
 In the United States, recycling (including
composting) diverted about 30% of solid waste
stream from landfills and incinerators in 2007.
• Benefits:
– Resource conservation
– Pollution reduction
– Energy savings
– Job creation
– Less need for landfills and incinerators
Methods of Waste Disposal
Recycling percentage for
selected materials (2007)
and recycling rates from
1960-2007.
Methods of Waste Disposal
 Container laws provide an economic incentive to
recycle.
• Requires a deposit on all reusable beverage containers.
• A national “bottle bill” would reduce litter, save energy
and money, create jobs, and help conserve natural
resources.
 Mandatory recycling laws provide a statutory
incentive to recycle.
Methods of Waste Disposal
 Curbside recycling provides a convenient way for
people to recycle.
• In 1990, 1,000 U.S. cities had curbside recycling
programs.
• In 2008, 11,000 cities had curbside recycling programs.
• Cities with curbside recycling tend to have higher
recycling rates than cities that lack such programs.
Methods of Waste Disposal
 In the U.S., curbside pick-up of recyclables is
increasingly the norm, but rates remain low.
 Recycle Bank was founded in 2004.
• Families on a garbage route are issued a container
with a computer chip. Recyclables are weighed and
the family earns points redeemable at merchants like
CVS pharmacy.
• Recycle Bank launched in Philadelphia in 2006.
– Recycle rates rose from 7% to 90%.
• In 2008 Recycle Bank started a pilot program in N.Y
at Columbia University.
– Students recycle and claim their points.
Methods of Waste Disposal
 There are many technical and economic
problems associated with recycling.
• Plastics are recyclable, but technology differs from
plastic to plastic.
– Milk containers tend to be high-density polyethylene
(HDPE), while egg containers are polystyrene (PS), and
soft-drink bottles are polyethylene terephthalate (PET).
Methods of Waste Disposal
Increasing amounts of plastic in trash
Methods of Waste Disposal
 The plastics industry is researching new
technologies.
 Economics of recycling are of concern.
• Unless demand for products keeps pace with growing
supply, recycling programs will face an uncertain
future.
Methods of Waste Disposal
 The long-term success of recycling programs is
tied to other economic incentives such as taxing
issues, and the development of and demand for
products manufactured from recycled materials.
 Government subsidies artificially lower cost of
virgin forest materials compared to recycled
materials.
 Demand for recycled products must grow if
recycling is to succeed on a large scale.
Methods of Waste Disposal
Recycling composite prices
Summary
 Municipal solid waste is managed by landfills,
incineration, composting, waste reduction, and
recycling.
 The most fundamental way to reduce waste is to
prevent it from ever becoming waste in the first
place.
 About 30% of the waste generated in North
America is handled through recycling.
Summary
 Future management of municipal solid waste will
be an integrated approach involving landfills,
incineration, composting, source reduction, and
recycling.
 The degree to which any option will be used
depends on economics, changes in technology,
and citizen awareness and involvement.
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