Landfills

For other uses see: Landfill (disambiguation).

Landfill is a waste disposal site for the deposit of the waste onto or into land (i.e. underground), including: Internal waste disposal sites (i.e. landfill where a producer of waste is carrying out its own waste disposal at the place of production), and a permanent site (i.e. more than one year), which is used for temporary storage of waste, but excluding: Transfer facilities where waste is unloaded in order to permit its preparation for further transport for recovery, treatment or disposal elsewhere, and storage of waste prior to recovery or treatment for a period less than three years as a general rule or storage of waste prior to disposal for period less than one year. [1]

In the U.S. each landfill falls under its States Environmental Agency, that lays down minimum guidelines; though no guideline may fall below that of the EPA. Most modern landfills require a minimum of one containment liner, consisting of a compacted clay with a minimum thickness and maximum hydraulic conductivity; compacted to 95% of maximum compaction. Others also require the addition of a layer of high density polyethelene (HDPE), as an impermable membrane.

In eras before the mid-20th century, landfills were the main method of waste management. In the late-20th century, alternative methods to waste disposal have been suggested, including recycling, converting to biodegradable products, incineration and cogeneration facilities, all of which assist in reducing the total amount of wastes disposed in to landfills.

A landfill may also refer to low-lying ground that has been filled in so that it can be used for a specific purpose, such as building houses. Soil and rocks are use to fill in the space instead of waste materials. Unless they are stabilized, these areas may experience severe shaking or liquefaction of the ground in a large earthquake.

Landfill classes

A landfill, based on the waste type that is disposed in it, can be classified as:

1. Hazardous waste landfill: waste disposal units constructed to specific design criteria and which receive wastes meeting the definition of hazardous waste.
2. Municipal solid waste (MSW) landfill: waste disposal units which receive household waste or wastes from other sources having similar composition as household waste but do not meet the definition of a hazardous waste.
3. Inert waste landfill: waste disposal units which receive industrial wastes that do not meet the definition of hazardous waste and which are chemically and physically stable and do not undergo decomposition.
4. Construction and demolition debris landfill: waste disposal units which receive construction and demolition wastes, such as sheet rock, wood, metal, roofing material.

Sanitary landfills, also called modern landfills or secure landfills, have physical barriers, such as liners and leachate collection systems, and procedures to protect the public from waste. The term sanitary landfill usually refers to municipal solid waste landfills with these sytems, but any class of landfill can be sanitary. In some countries, all landfills are sanitary landfills. A good example of a sanitary landfill can be found in Cache Creek (see Ashcroft, British Columbia) British Columbia where the Greater Vancouver Regional District in the Province of British Columbia, Canada, disposes of most of its waste.

Landfill requirements

All landfills must be constructed and operated in accord with specific requirements, which are related to:

• Location or siting requirements.
• Stability.
• Protection of soil and water through:

-Installation of liner and collection systems.

-Storm water control

-Leachate management.

-Landfill gas management.

• Nuisances and hazards management.

Landfill subsystems

A typical landfill consists of subsystems such as the:

• Bottom liner system.
• Leachate collection and management system.
• Landfill gas management system.
• Monitoring system.
• Road network.
• Drainage system.
• Final capping system.

Their function is to secure the normal landfill operations and to control the anticipated emissions generated mainly by the decomposition of organic matter, such as leachate and landfill gas.

Landfill operations

Typically, in non hazardous waste landfills, a technique is applied by which the wastes are:

1. Confined to an as small area as possible.
2. Compacted to reduce their volume.
3. Covered (usually daily) with layers of earth,

in order to meet predefined specifications.

Landfill operation. Note that the area being filled is a single, well-defined "cell" and that a rubberized liner is in place (exposed on the left) to prevent contamination by leachates migrating downward through the underlying geological formation.

Description of landfill operations

During landfill operations the waste collection vehicles or garbage trucks are weighed at a weighbridge on arrival and their load is inspected for wastes that do not accord with the landfill’s waste acceptance criteria. Afterwards, the waste collection vehicles use the existing road network on their way to the tipping face or working front where they unload their load. After loads are deposited, compactors or dozers are used to spread and compact the waste on the working face. Before leaving the landfill boundaries, the waste collection vehicles pass through the wheel cleaning facility. If necessary, they return to weighbridge in order to be weighed without their load. Through the weighing process, the daily incoming waste tonnage can be calculated and listed in databases.

Typically, in the working face, the compacted waste is covered with earth daily. Alternative waste cover materials are several foam products and temporary blankets. Foams must be sprayed on. Blankets can be lifted into place with tracked excavators and then removed the following day prior to waste placement. The space that is occupied daily by the compacted waste and the cover material is called daily cell. Waste compaction is critical to extending the landfill's life. Factors such as waste compressibility, waste layer thickness and the number of passes of the compactor over the waste affect the waste densities.

Problems during landfill operations

A number of problems can occur during landfill operations. The consequences of these problems, depending on their nature and severity, vary from fatal accidents (e.g. scavengers buried under waste piles) to minor infrastructure damage (e.g. potholes on access roads) and from environmental pollution (e.g. leak of major leachate quantities to the underground bed and/or aquifer) to simple nuisance problems (e.g. dust, noise). Analysis and advice on common landfill operational problems are available in [2].

Social issues

Some local landfill authorities have found it difficult to locate new landfills. These authorities may charge a "tippage fee" in order to discourage waste or recover the costs of site operations. Many landfills, however, are publicly operated and paid for by taxes. For many areas, a well-run landfill is a hygienic, inexpensive solution to garbage disposal. Poorly run landfills can pollute both air and groundwater.

Environmental activists dislike landfills not only because of the potential for pollution, but because they permanently remove various raw materials from economic use. All of the energy and natural resources (such as water) that were used to produce the items "wasted" are lost. This loss is said to contribute to damage of forests and agricultural areas, including in less-developed countries that derive a majority of their export revenues from raw materials. However, recycled materials compete in the marketplace with new materials. Most of the discarded materials are low in value, making it difficult to profit from their sale. This in turn reduces motivation to recycle.

Landfill history

The "Fresno Municipal Sanitary Landfill", opened in Fresno, California in 1937, is considered to have been the first modern, sanitary landfill in the United States, innovating the techniques of trenching, compacting, and the daily covering of trash with dirt. It has been designated a National Historic Landmark, underlining the significance of waste disposal in urban society. More information on landfill history in the United States can be found in [3].

See also

• list of landfills in Hong Kong

References

• Council Directive 1999/31/EC of 26 April 1999, on the landfill of waste. URL accessed on August 29, 2005.
• The Landfill Operation Management Advisor Web Based Expert System. URL accessed on August 29, 2005.
• H. Lanier Hickman Jr. and Richard W. Eldredge. Part 3: The Sanitary Landfill. A Brief History of Solid Waste Management in the US During the Last 50 Years. URL accessed on August 29, 2005.