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A 'garbage disposal', 'waste disposal unit', or 'garburator' (Canada) is a device, usually electrically-powered, installed under a kitchen sink between the sink's drain and the trap which shreds food waste into pieces small enough to pass through plumbing. Garbage disposal units are widely used in North America. The European Union does not authorize food waste disposals per EN 12056-1, § 4.6, but countries or counties may do so, which they rarely do.^[1] There are regulations on their installation and use in many countries. Some say that sewage treatment plants cannot cope with the extra load of kitchen waste disposal units. However the scientific literature does not give any proof about this.
Many standard disposal units allow a dishwasher to be connected, and some dishwashers are equipped with a small built-in garbage disposal unit, making it unnecessary to scrape plates before washing them.

Contents

History

Operation

Selection

Environmental impact

Cultural References

External links

References

History

The garbage disposal was invented in 1927 by John W. Hammes. Mr. Hammes was an architect working in Racine, Wisconsin. After eleven years of development, his In-Sink-Erator company put his disposer on the market in 1938.
In many cities in the United States the municipal sewage system had regulations prohibiting running food waste (garbage) into the system. In-Sink-Erator spent considerable effort, and was highly successful in convincing many localities to rescind these prohibitions.^[2] Many localities mandated the use of disposers.^[3] For many years, garbage disposals were illegal in New York City because of a perceived threat of damage to the city's sewer system. The ban was rescinded on September 11, 1997 by local law 1997/071 which amended section 24-518.1, NYC Administrative code.^[4]
Garbage disposal units became popular in American kitchens of the better-off in the 1970s and 1980s. The EU prohibited the use generally with the option for member countries to make exceptions, but there are only few countries allowing its use, and local authorities generally emphasize the prohibition: the reason is supposedly the additional load on sewage treatment plants which would make sewage treatment more expensive than the composting of kitchen waste.^[5] Forty-seven percent of U.S. homes, but 6% in the United Kingdom, had disposal units as of 2007.^[6]

Operation

A high-torque, insulated electric motor, usually rated at 200–750 watts (¼ to 1 horsepower) for a domestic unit, spins a circular turntable mounted horizontally above it. Induction motors rotate at 1,400–1,800 rpm and have low starting torque; commutator motors rotate at higher speeds (about 2,800 rpm), have high starting torque, and are usually lighter^[7]. However commutator motors are noisier than induction motors, partially due to the higher speeds, and partially because the commutator brushes rub on the slotted armature^[8]. The higher starting torque of those appliances with a permanent magnet motor secures in most cases that there will be no blockage.
The added weight and size of induction motors might be of concern. Many models have some degree of sound insulation.
The turntable is surrounded by a shredder ring, which has sharp slots. The food waste sits on the turntable, and through centrifugal force is forced to its perimeter and through the shredder ring. The turntable has a number of swiveling lugs—similar to little hammers attached to its topside, which assist in forcing the waste through the shredder. Except for special models, most of the Food Waste Disposers do not have any sharp blades or scissors.
Waste is fed into a chamber above the turntable and drops on the turntable. The chamber may have a rubber partial closure through which waste can be pushed without letting cutlery and other objects fall in, but essentially the chamber is open at the top, and there is access to the turntable. This is useful in the case of a jam: the turntable can be forced round by pushing with a wooden spoon handle or similar object until the jam clears. Waste which cannot be ground successfully can be removed manually.
Most units are of the continuous-feed type, allowing waste to be added as the unit runs. Batch-feed models are also available with a lid which must be locked before operation, making it impossible to run the machine when a user is trying to clear a jam by hand, and preventing cutlery, etc. from falling in.
Some commercial and high-end domestic disposals also have an undercutter blade which revolves below the turntable and chops the ground waste, including fibrous material which could cause a drain clog, finer. These disposals can handle fibrous waste such as artichoke leaves which cannot be successfully ground in a standard disposal.
Waste disposal units may jam, but can usually be cleared either by forcing the turntable round from above, or by turning the motor using a hex-key wrench inserted into the motor shaft from below. Very hard objects accidentally or deliberately introduced, such as metal cutlery, can damage the waste disposal unit and become damaged themselves. More problematical are drain blockages caused by shredded waste which is fibrous (artichoke leaves) or starchy (potato peelings).
Some higher-end units have automatic reversing. By using a slightly more-complicated centrifugal starting switch, the split-phase motor rotates in the opposite direction from the previous run each time it is started. This can clear minor jams, but is claimed to be unnecessary by some manufacturers as since the late 1970s most disposal units have swivel impellers which make reversing unnecessary.^[9]
Another kind of garbage disposal unit is powered by water pressure rather than electricity, and does not pose an electrical hazard.^[10] Instead of the turntable and grind ring described above, machines like the hydromaid (from the company with the same name) are water-powered units have an oscillating piston with blades attached to chop the waste into fine pieces.^[11] Because of this cutting action, they can handle fibrous waste and even glass (not recommended). If an item too hard to process falls in, e.g. cutlery, no harm comes to it or the unit as the blades just stop. Water-powered units take longer than electric ones for a given amount of waste, and need fairly high water pressure to function properly.
Cold water should always be kept running when the disposal is switched on to prevent damage to the blades and wash away the chopped waste without allowing it to build up and clog the drains. Hot water tends to dissolve easily-flushed solid shredded pieces of fat, which can then solidify and block the drain.
Provision must be made to supply and switch power to the waste disposal unit. A conventional electric switch can be used, which requires wiring to be installed and poses a potential electric shock hazard if used with wet hands. An air switch which delivers a puff of air to operate an electric switch remote from the operator is safer. Alternatively, a wireless remote control switch can be used.

Selection

Selection of a garbage disposal unit should be based on quality and performance. Motors are relatively trouble-free, and unlikely to fail during a reasonable life-span. Metal parts in contact with waste and water (turntable, lugs, chamber, shredding ring) are very prone to corrosion, and should be made of stainless steel or similar corrosion-resistant material rather than non-stainless steel, even if galvanized. The length of manufacturers' warranties gives some indication of quality, but most units should last very much longer than their warranty period.
The size of the chamber and power of the motor (in horsepower or watts) determine the amount of waste processed per unit time. Soundproofing to reduce the noise of operation adds cost.
Induction and commutator motors each have advantages and disadvantages. Feed can be continuous or batched.
Some manufacturers use standard mountings for all their models, making it very easy to replace a unit by any model of the same brand.

Environmental impact

Use of garbage disposal units diverts the impact of garbage from methods such as landfill or incinerators to effluent disposal systems. The advantages and disadvantages need to be weighed for each area.
It is often said that the vast majority of organic waste would be better used for composting, an option not open to many city-dwellers.
Energy usage is not high; typically 500 to 1500 watts of power are used, but only for a short time.
Daily water usage varies, but is typically comparable to flushing a toilet a couple of times[1].

Cultural References

★ A garbage disposal features prominently in an opening scene of Robert Redford's 1980 movie ''Ordinary People''.

★ A garbage disposal is featured in 1981's ''The Incredible Shrinking Woman'' when Lily Tomlin's character "Pat Kramer" falls down the drain and is almost chopped to bits by her family.

★ The character of Claire Bennet on the TV series ''Heroes'' severely (and intentionally) mangled her hand in an active garbage disposal unit in the series pilot. This led to a lawsuit by the makers of the particular brand.

External links

★ Page with garbage disposal research

References

1. European Norm EN 12056, §4.6, Brussels:CEN 1986
2. Cox of In-Sink-Erator dies of cancer at 84, Contractor, July 1999
3. Insinkerator on its heritage
4. NYC Council Issue 1997
5. German MP replies why the disposer is not allowed in the EU, p. 37
6. Guardian, August 6, 2006, Two Counties allow Food Waste Disposal
7. Garbage Disposal power on Nettally.com
8. Noise from universal motors vs. induction motors at howstuffworks.com
9. Magnet and induction motors in Commodore Disposers
10. Specifications of a water-powered food disposer
11. New Garbage Disposal Runs on Water Power, LA Times, April 5, 1998