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Waste management

Waste management is literally the process of extracting value from waste. Waste management and sewage treatment institutions normally are responsible for mass efforts to recycle wastes.

Until recently, in industrialised contries with large amounts of land, it has been customary to place garbage in landfills, or incinerate it.

Some local landfill authorities have found it difficult to locate nearby landfill areas, because of political opposition from landowners concerned about lowered property prices. Some of these areas have begun to tax garbage[?] production, and legally mandate "source reduction" to increase the lifetime of the established landfills.

Most areas in most countries have enough land for landfills. For many areas, a well-run land-fill is a hygienic, inexpensive solution to garbage disposal. Poorly run landfills can pollute groundwater, and the air. (For management methods, see landfill)

Ecological activists dislike landfills not only because of the potential pollution, but because they permanently remove raw materials from economic use. Note that this argument also applies to incineration, as well. Not only are the materials are wasted, but also all of the energy and natural resources (such as water) that are used to process them. This 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.

One of the problems is that recycled used materials compete in the marketplace with new materials. Most of the discarded materials are low in value.

However in many areas garbage has enough value to justify recycling parts of it, rather than disposing of it in a landfill. Jurisdictions with a container return-deposit law can often fund recycling industries just from collections of return deposits. In industrialized countries, the bulk of unprocessed landfills, by weight, consists of paper products. These usually include newspapers, packaging and building materials, magazines and used disposable diapers[?] and sanitary items. These items often have a small value as pulp recycling feedstocks or incinerator powerplant fuel.

In some areas, as much as 40% of landfills consist of waste from demolished buildings. These can be reduced by sustainable design.

In southern California, some waste services already separate recyclable wastes from household garbage. The separation process produces relatively pure streams of paper, plastics, glass, steel, copper and aluminum. Toxic wastes are usually easy to identify and segregate.

The process starts with the trucks, which collect garbage in cans from streets, and from dumpsters and compacting dumpsters in businesses.

The trash is dumped to a conveyor belt. Workers remove whole bottles to a special conveyor belt. Whole bottles and cans go to a machine that reads the product bar code, and sorts the container by its color of glass, metal or resin type. The bottles' return deposits are then recorded (they're being recycled, an acceptable use).

Theoretically, the resin identification code may be used to separate miscellaneous plastic materials. However the low value of most resins, and the need for expensive manual identification and disassembly currently make such recycled resin too expensive for most operators to compete with resin from new feedstocks.

Most plastic resins can be recycled by applying steam, pressure and high heat. These separate most resins into monomers that can be refined and repolymerized.

An entrepreneur recently discovered that a similar process can depolymerize and reduce (remove oxygen from) organic wastes such as paper, slaughterhouse offal, hair and feathers. The result is a light crude oil suitable for fuel or sale.

Also during manual sorting, suspicious packages, such as bottles of paint or motor oil containers, are separated into toxic waste containers.

Some operators recycle motor oil by selling it to a reclaimed motor oil company. Motor oil recyclers normally perform fractional distillation to separate usable compounds. The waste is sometimes catalytically cracked to get more motor oil, and the sludge is sold as asphalt.

The remaining waste is mostly paper, plastic and miscellaneous trash. It goes to a separator. The separator dumps the trash down a wind-tunnel that blows paper into a separate container, to be pulped. In the pulper, which is often at a separate paper plant, plastics and foreign objects are removed, chopped and run through the waste process again.

The non-paper waste goes to a hammer mill, which produces very small pieces of waste. These are run past a powerful magnet. Iron and steel waste is extracted. Conductive metal waste such as aluminum, silver and copper are pushed away from the magnet by inverse magnetic fields produced by eddy currents in the conductive materials. Nonconductive, nonmagnetic ceramic, glass, plastic and woody waste fall straight down.

Mechanisms similar to the hammer mill and separator are also used to process scrapped automobiles and appliances.

The small amount of nonconductive solid waste is inert, usually flammable and not very valuable. In California, because of extremely strict air pollution control laws, it must go to a landfill, rather than being incinerated.

A continuing problem with recycling is that common recyled materials such as paper are often of slight or negative value compared to new materials. At times, supplies of paper or plastics can swing, permitting economic recycling of paper, glass or selected plastics. A waste-management organization must track such prices and be prepared to divert its resources to higher-paying uses.

In many areas of Europe, including France, Germany, Italy and Switzerland, such low-value recyclable waste (mostly paper and plastics), is incinerated, often with some amount of added natural gas.
Incineration reduces the waste volume by 95%, and sanitizes the waste of biohazards and unpleasant smells.

Incineration is often used to produce electricity. If toxic materials (such as chlorinated plastics) are removed, and incineration is completed at controlled temperatures, little pollution is produced.

Separated trash is excellent for feeding incinerators. However, separation increases economic risks. Frankfurt, Germany is said to have experienced a power-generation crisis when it introduced waste-separation. Many of the previously-incinerated materials proved to have slightly more value as recyclable feedstocks than as electricity!

Incinerator ash is toxic, and its leachate can poison groundwater[?]. Until recently, safe disposal of incinerator waste was a major and continuing problem. In the middle 1990s successful experiments in France and Germany used electric plasma torches to melt incinerator waste into rounded glassy pebbles, valuable as concrete filler. The glassy pebbles of waste do not dissolve in water.

An alterative use for incinerator ash has been to chemically separate it into lye and other useful chemicals. This is usually done at a central national chemical plant. The processes produce unsalably small amounts of chemicals when performed on a small scale at a city. At existing plants, the unsalable toxic chemicals are released as effluent in rivers and as toxic solid wastes. It might be economical to dry and recycle unsalable fractions through plasma torches as concrete fill.

Articles about, or including aspects of, recyling:

See also:



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