MANAGING OUR WASTES: A SUSTAINABLE APPROACH

 

Ÿ         The United States is by far the World's leader in GARBAGE and the world's leader in Hazardous waste generation.

Ÿ         By one estimate, the US produces an estimated 200 to 250 million metric tons of hazardous waste each year. This translates into approximately 1 metric ton for every man, woman and child in the country.

Ÿ         In 1990, American cities and towns produced 175 metric tons of Garbage, or MUNICIPAL SOLID WASTE from homes and businesses (not industries). Added to this was over 70 million metric tons of solid waste that is produced annually from industries.

Ÿ         Complicating matters further, the Municipal solid waste production is increasing at a rate of 2% to 4% a year. This will result in the Doubling of the Garbage Output in 35 years.

 

PER CAPITA WASTE GENERATION RATES IN SELECTED CITIES - 1996

 

Developed Countries

 

SELECTED CITIES

KILOGRAMS PER DAY

Los Angeles

3

New York

1.8

Tokyo

1.38

Paris

1.1

Singapore

0.87

Hamburg

0.85

Rome

0.69

 

Developing Countries

 

Lahore, Pakistan

0.6

Tunis, Tunisia

0.56

Calcutta, India

0.51

Kano, Nigeria

0.46

 

 

 

 

Problems posed by Solid Waste Disposal:

 

·    It is expensive. For example, the US currently spends over $300 million a year just to landfill disposable diapers. In many cities, waste disposal is the second largest expenditure after education.

·    Solid waste disposable often takes up valuable and costly land. In the absence of a landfill space, waste haulers must ship garbage many miles at huge expense.

·    Landfills pollute groundwater while incinerators cause air pollution

·    Garbage disposal and incineration represent a waste of valuable resources. Aluminum cans and other metals when recycled could be a valuable resource. Throwing away these resources thus cause the exploitation of more resources

 

Sustainable management of Solid Wastes:

 

Three approaches can be adopted to attain a sustainable management of Solid Wastes. These include:

     a)  Reduction Approach - which calls for lower levels of material consumption in society.

b)         Reuse and …

c)           Recycling Approach - which attempts to maximize the life span of a material in the production-consumption cycle.

 

Reduction Approach:

 

This approach calls for reduction in the per capita consumption of natural resources through one or more of the following approaches.

·    Purchase more durable items

·    Buy more efficient products - automobiles, houses and appliances.

·    Cut consumption by reducing luxury items.

·    Manufacturers can reduce the sizes of their products so to cut down on material used per unit

 

Reuse and Recycle Approach

 

Ÿ         Japan, Mexico, North Korea and Netherlands are leaders in Paper Recycling.

Ÿ         Advocates of the Reuse approach calls for a continuous use of materials in an attempt to cut down on the consumption of new resources. For example, boxes, clothes, appliances that may be trash-bound could be donated to others for reuse.

Ÿ         Recycling is another form of Reuse but usually involves some form of conversion from one state of the material to another. For example, in recycling, a glass will have to be crushed and melted before it will be used to make a new glass.

 

Composting: a form of recycling that occurs when organic matter such as kitchen wastes, yard waste (leaves and branches) and even paper and cardboard are allowed to decompose.

 

EVOLUTION IN METHODS OF URBAN WASTE DISPOSAL

 

1) Waste Dumps

Dumps are open sites where trash are deposited and occasionally burned to reduce the volume of the accumulating garbage. Earliest form of waste disposal currently abandoned in economically advanced countries but common in poor developing countries.

 

Problems:

1.           Attracts rats and flies

2.           Wind shifts brings an odorous smell to offend residents living close to the dump

3.           Burning the garbage causes black smoke, filled with toxic byproducts from burning

rubber, plastic etc to fill the air.

4.           Rain and snow melt trickle through the garbage and carry materials into surface and

groundwater supplies

 

2)  Sanitary Landfills

A sanitary landfill is an excavation, or a hollow in the ground in which garbage is dumped, compacted and covered daily with a fresh layer of dirt.

Advantages:

·    It reduces odors caused by the rotten garbage and prevents air pollution caused by periodic burning of waste in an open dump.

·    Because a soil layer is placed over the trash, compacted, and then generally sloped to reduce water percolation into the garbage, groundwater contamination can be greatly reduced.

·    The protective layer of soil also reduces insects and other pests that could carry disease.

·    The garbage can also be reclaimed - returned to some previous use. For example, a stadium or a shopping mall can be built on the site. In Denver - Colorado, a shopping mall, stadium and a park have been constructed on former landfills.

 

Disadvantages:

·    If the soil or rock is permeable, there could be a considerable seepage that would lead to groundwater pollution.

·    Rotten debris produces methane, which is a potentially explosive gas.

·    Requires large tracts of expensive land

 

3)  Incineration

 

It is a system in which unseperated trash - containing plastics, metals, paper, yard waste and glass - is burned and the heat produced during combustion is often used to generate steam for industrial processes, home heating or electrical power generation.

 

Advantages:

·    It captures energy that would otherwise be lost.

·    It requires less land than landfills and Dumps.

 

Disadvantages:

·    Incinerators that burn plastics and other materials containing chlorine emit a dangerous class of compounds called Dioxins that have been linked to cancer and weakens the immune system.

 

MANAGING HAZARDOUS WASTES

 

Like municipal wastes, hazardous wastes can be dealt with in three basic ways:

a)  Reduction Approach  b) Reuse & Recycling, and c) Discard Approach

 

1.  Reducing Hazardous wastes:

·    Modify or redesign the manufacturing process that create hazardous wastes

·    Substitute safe materials (e.g. biodegradable) for more harmful ones

 

2.  Reusing & Recycling Hazardous Wastes

 

3.  Detoxification:

Some toxic wastes cannot be reused or recycled but are amenable to biological, chemical and physical detoxification. For example, organic wastes such as DDT, PCB's and even Dioxin can be burned in high-temperature incinerators to convert the harmful organic substances into relatively harmless carbon dioxide.

 

4.  Secured Landfills

It is usually a clay-lined pit designed to hold hazardous wastes

 

5.  Deep Injection Wells

Deep wells are drilled in the earth’s crust into porous rocks sandwiched between impermeable rock layers. In theory, the hazardous material is believed to remain in place forever but this may not always happen.