Garbage Disposals

  •   January 12th, 2015
  •   Category: News
  •   Posted by: Ecodyger

First of all it would be more correct to call them heat sinks and not garbage disposals. In America they are known as Food Waste Disposers. Very popular in the US and partly in the United Kingdom and Sweden, they have always been considered a mysterious object or nearly in the rest of the world, where their use has often raised debates between the institutions and water and public sewer managements. Why? Simple, used on a large scale is said to clog purifiers. We will deepen the topic later.

In Italy they are known as DRA and can be installed, under the control of the managing body of the networks and systems of water purification.

It’s a real appliance, applied under the kitchen sink at the discharge of the sink.


It permits to throw the wet waste in the kitchen sink and send it into the plumbing and sewerage. Of course, any intervention should be done after checking the compatibility with your system, the ones dated do not go well because of the small diameter of the pipes used, often still in lead.

A bit of history

FWD_old version_01

Its first appearance was in 1927, invented by mr. John Hammes, an American architect of Racine, Wisconsin. His patent application then goes back to 1933 with the official release in 1935. His company InSinkErator, that over the years became very popular in the US and then in the world, put the heat sink on the market in 1940.

For the record, there was a dispute of Hammes against the US giant General Electric which introduced a system of waste disposer in 1935. In many cities of the United States in 1930 and 1940, the municipal sewage system had regulations that prohibited the emission of food waste (garbage) in the system. InSinkErator spent a considerable effort and convinced many places to lift such bans. The last resistance occurred in cities like New York, where the dispute ended only in the nineties.

How does it work?

The garbage disposal, chops and minces food scraps by a mechanical movement of special ” screeds ” ( small metal hammers ) placed at the end of the inner walls of the grinding chamber, that turn into mush what is inserted into the disposer with running water. We disclaim then the urban legend that describe the disposals equipped with sharp blades and cutting edges.


The scraps are transformed into a soggy mush which then slips away diluted with tap water, moving from the grinding chamber of the disposer to the sewer system through the exhaust ducts.



In summary, these are the actions to be taken:

  1. open the tap and let it run;
  2. turn on the waste disposer;
  3. put organic waste in the sink and make it gradually drain into the sink exhaust with water;
  4. Wait for the disposal to complete the operation to reduce the gap to a pulp ( it is perceived easily by the noise that fades );
  5. turn off the waste disposer.

What can I dispose

Fruits, nuts, fish, shellfish, mussels, vegetables, bones ( chicken and rabbit), pasta, egg shells, fruit pits, coffee grounds

What I cannot dispose

Many manufacturers of waste disposers merely indicate that ” everything that’s not organic waste is not disposable.” In reality it is known that all the fibrous vegetable / filamentary waste such as artichoke, celery, fennel, etc.. create problems because they tend to create ” fibrous bullets ” that actually clog the pipes. Also, you cannot dispel all the large bones as well as paper towels that normally go in the bin instead of wet waste collection.


It reduces the mass of food waste in house or at commercial catering activities, leaving no unpleasant odors and reducing air pollution because it would remove from the streets vehicles dedicated to the transport of wet with their CO2 emissions.

The 4 disadvantages of garbage disposal

Objectively, the device also has several disadvantages, which must be taken into account.

1) First of all implies a huge waste of drinking water to drain the shredded material. For example, to dispose of a quantity of wet waste between 100 and 500gr a domestic waste disposer employs an average of 1 minute; a normal kitchen tap disposes 10 liters of water per minute. On average, the daily use of a waste disposer involves wearing a water consumption of more than 30-35 liters.

This water consumption surely goes against the policy of “Water footprint” which is an indicator of the consumption of fresh water that includes both the direct and indirect use of water by a consumer or producer (see link)

2) At the same time there is a considerable absorption and energy consumption; domestic models have powers of up 750-1000 Watt consumption directly proportional to minutes per day and the consistency / resistance of the waste treated.

3) In addition, the disposer can not mix into very fine particles, with the risk of clogging the pipes of internal housing and those of the road sewer, not designed to carry a large amount of fluids of this type. This is especially true when trying to dispose of waste.


4) Finally, the crushed substances ranging from sink to collect the sewage system require a long process of decomposition by bacteria in the sewage system and increase the amount of sludge in municipal wastewater. This mud is quite difficult to be disposed of in landfills or by incineration.

Love them or hate them?

We have already seen in all previous articles in the blog that the issue of organic waste is complex. And if composting is the best practice for many, others argue that involves emissions. For sink waste disposers the risk is, as already mentioned above, the overload of the sewer system.

Popular in the US, almost ignored in Italy, they clog strainers, but save and produce biogas. In Italy for example, there are those who opposes sink disposals because of the discharge into public sewer of compostable material and there are those, however,who considers them friends of the environment.

Case history: Chieri (Turin, Italy)

Source: Corriere della Sera / Sette Green

The Company of underground waters in Turin ( SMAT ), between 2010 and 2011, with the chemistry department of the University of Verona and the Polytechnic University of Turin, Ato – R, the organization responsible for the waste water, the federation of industrial Ani- elp ( Union enterprises defense environment ), has created a research project on the use of sink waste disposer in the city of Chieri.

The Purpose : To evaluate the technical and economic impact of the heat sinks. In the first part of the study was defined as the residual potential of the purifier, which can be filled by waste streams of dissipated food. The purifier of Chieri is sized on about 60 000 inhabitants but it is used by 30-40 thousand, therefore, has a remaining capacity that can be used with organic waste derived from the installation of more than 4,100 food disposals.

“Chieri’s system is missing anaerobic digestion of sludge and primary sedimentation, and currently does not allow the production of biogas from organic material, collected through urban sewer,” explained the scientific director of the study. “But mixtures of sludge and organic fraction are an excellent substrate for a compost from co-digestion of high quality.”

We know that food waste of plants and animals origin in the landfill are among the causes of the production of natural gas and among the most responsible for the greenhouse effect and for that the European regulations ask the mid- nineties the reduction of organic waste disposed of in landfills

But where the collection of organic waste has not been started, the companies that manage the waste water are ready to dispose of organic waste reduced to a pulp ? We return to respond to the experience of Chieri. The managers of the water and sewerage in Turin, partner in turn in the study in question,at the conclusion of the same, have banned sink waste disposers in Turin and its surroundings.

This is their conclusion: ” The managers of water service don’t believe that at the time in the territory of Turin the discharge into the sewer system of organic waste through food waste disposers equipment can be allowed.

In Pinerolo, Turin, a warning for users states: ” The discharge into the sewer system of organic waste through the use of food waste disposers and grinders to be installed under the sink is prohibited.”

Experts don’t like them

We’ve seen that the problems that may arise are the functionality of the networks. Due to the presence of organic material, the functionality may be compromised, and the overload could result in the revision and upgrading of wastewater treatment plants.

According to experts of composting, it would not be just a matter of discharges.
“The spread of the waste disposers, not only would contribute to clogging of the drainage system, and in fact the ministerial circular speaks of preliminary technical assessment of the networks by the operator of the plant,” says the CIC, Italian Composters Consortium. ” This would cause a sharp deterioration of the quality indices of the compost produced. If the moisture that goes into the sewer system would be composted with an aggravating circumstance that would come into the system with the sludge. This would decrease the quality of the finished compost that would also contain heavy metals and organic pollutants in sludge”.

Pros and Cons

In short, according to the manufacturers, the sink waste disposer is “environmentally friendly ” because reduces into a pulp biodegradable waste that flows away through the drainage system and saves emissions, preventing that organic waste is disposed of in landfills, produces sewage sludge that can be recover in agriculture.

For Legambiente, instead, the waste disposer is not environmentally friendly. The wet waste must be sent to composting through curbside collection and not into the sewer. The plumbing underground is not equipped, and also 18 million Italians are not served by treatment plants: this means that discharges of 18 million of Italians go into rivers, lakes and sea. “

Modern solutions: Ecodyger

Leaving to you readers the feedback on the above, we like to point out how Ecodyger (see link) overlooks this difficult scenario as a more modern solution. Ecodyger is placed on top of these issues, for us, as indicated by the European Directive on Waste.
The common goal should be to make prevention and produce less waste at source and consequently collect and transport less and less.

Just so you can have a real and meaningful reduction of CO2 emissions which is the true and only goal of the entire international community.

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Image: The Flintstones