Kitchen garbage grinder
A kitchen waste shredder (KAZ) is a device that is widespread, particularly in the USA , for shredding organic kitchen waste, which is usually attached directly to the drain in the kitchen sink . Biodegradable waste from private households and small businesses is crushed into about 2 mm particles so that it can be flushed through the sewage system into the sewage treatment plant with normal kitchen waste water.
In addition to the simple disposal route for the user, there can be an advantage in increasing the production of sewage gas in digestion towers of sewage treatment plants.
General
The waste is finely divided in the kitchen waste shredder with running water by motor power and transported as waste water via the public sewer system to the sewage treatment plants.
The first kitchen waste shredder was developed in 1927 by John Hammes in the USA and brought onto the market there in the following years by his company, which was founded in 1938. The number of shredders in use is estimated at around 75 million in the USA and around 120 million worldwide.
Features and function
The devices are about 30 centimeters high and have a diameter of 15 to 20 centimeters. They are installed between the sink drain and the siphon below the kitchen sink and operated with normal mains voltage. The water drainage is guaranteed even when the device is switched off.
Kitchen waste falls through the sink drain onto a rotating disc on which small, movable hammers are attached, which press the waste against the wall using centrifugal force, where small sharp-edged holes (about half a centimeter in diameter) crush them until they pass through them flushed down the drain. Long-fiber food waste such as B. leeks or banana peels can only be processed crosswise by some devices without interference.
The turntable typically rotates at 1400 to 2800 revolutions per minute. The power consumption of the motors is between 200 and 1500 watts.
distribution
Kitchen waste shredders are used around the world, but mostly in the US, where 50% of households owned such an appliance in 2013. They are little known in most other countries.
In Europe they are explicitly approved in some countries:
- Denmark
- United Kingdom: Citizens receive grants to buy kitchen waste grinders in some municipalities.
- Ireland
- Italy
- Norway
- Sweden
- Spain
German manufacturers offered kitchen waste shredders at least temporarily in the 1950s. The Alexanderwerk company, for example, produced a corresponding model.
Legal situation
Kitchen waste shredders can be approved in the EU . It says in EN 12056-1 Chapter 4, Paragraph 6: “The requirements for the quality and the volume flow of wastewater which is fed directly into the public sewer network are the subject of national and regional regulations and technical rules and must be observed. The ingress of substances into the system that interfere with its effectiveness or that have not been approved by the responsible authorities must be prevented. National and regional regulations and technical rules may permit the use of waste shredders ”.
In Germany , as in many EU countries, such approval is mostly refused. DIN 1986-100, No. 6.5 of October 2001: "Shredding devices for kitchen waste, rubbish, paper, etc. as well as towel dispensers with flushing devices, in which the shredded wash items can get into the drainage system, may not be connected to the sewage system," however Device no longer mentioned in the successor regulation 12056. There is no national ban in Germany, but most municipalities explicitly prohibit the discharge of kitchen waste, even in shredded form, in their drainage statutes.
In Switzerland , the Waters Protection Ordinance prohibits “disposing of solid and liquid waste with wastewater” and thus the use of kitchen waste grinders.
In Austria , the installation and operation of a kitchen waste shredder is prohibited in accordance with the Water Act (WRG) and Waste Management Act (AWG). If such offenses become known, the responsible district administrative authority must order measures to restore the legal status. In addition to the criminal proceedings to be initiated, the authority must also arrange for the proven removal of these devices.
background
In 2003 and in the years before that, Fricke carried out detailed investigations into throwaway behavior at home. The proportion of organic waste in household waste was determined to be 33–51 percent by weight. The proportion of organic waste has only decreased to 27–39%, even with the organic waste bin, and still makes up the largest proportion of residual waste.
Kitchen waste consists of up to 90% water, so it makes sense to dispose of it together with the wastewater. In addition, organic kitchen waste is often disposed of in the toilets. A previous comminution is advantageous, as comminuted particles can run off better in the sewer pipes. Just as human waste and toilet paper are composted in the digestion tower and processed into biogas, this can also be done with shredded kitchen waste.
Landfilling of untreated waste has been largely banned in the EU since mid-2005. In Germany there is hardly any landfilling anymore. The so-called residual waste is incinerated. With the help of the KAZ, the volume of residual waste could be significantly reduced. Cost advantages for the citizen are conceivable if organic bins can be saved.
The immediate disposal of biowaste in the shredder prevents the formation of molds , the mycotoxins of which can be absorbed via the lungs and especially harm allergy sufferers and other health-prone people (see also organic waste bin ) .
Some sewage treatment plants suffer from a poor C / N ratio and, in order to achieve the limit values for nitrogen required by law , have to add carbon to the wastewater in order to be able to carry out denitrification . Today this is mostly done by adding carbon sources such as B. methanol , sugar , acetic acid, etc. achieved. Due to the carbonaceous kitchen waste, the addition can be unnecessary. Sewage treatment plants with a high proportion of nitrogen-containing urine in the wastewater add partially shredded biowaste to the wastewater.
Especially in large cities without fully and reliably functioning garbage disposal systems, the disposal of organic waste via the sewer system can contribute to the containment of animal disease carriers that feed on improperly disposed organic waste. Disposal via wastewater seems to be advantageous in many cases from an environmental point of view, as long as composting is not possible and the municipal sewage sludge is sensibly recycled.
Advantages over composting organic waste
Wet organic waste must often be mixed with green waste for composting, because in the composting in the compost heaps otherwise anaerobic zones and greenhouse gas (mainly methane form). Alternatively, this can also be prevented by frequent repositioning of the windrows during rotting, which however usually requires the use of fossil energy (e.g. diesel fuel for the tractor). Electrical energy is used in drum systems.
The municipal waste management department charges an average of 50 euros per year for the regular disposal of the contents of a bio bin.
The so-called co-fermentation is being operated in German sewage treatment plants with increasing tendency . Decomposable waste with a high water content and a sufficiently high energy content is fermented together with the sludge from the primary clarifier in the digester. The resulting biogas ( called sewage gas in sewage treatment plants ) with a high proportion of methane is converted into electricity in the plant. The waste heat is used to heat the company building and digester.
Conventional composting inevitably produces greenhouse gases such as B. methane. The energy content of 3.9 MJ per kg of kitchen waste, on the other hand, can be made usable in the context of co-fermentation in the digester of the sewage treatment plant by using these gases to drive gas turbines.
In 2007 around 6 million tons of bio-waste were collected nationwide, for which the citizens were charged fees of around 800 million euros at an average cost of 100 EUR / ton. If kitchen waste grinders were used, these sales would be severely reduced. Citizens would not only save garbage fees, the wastewater fees could also fall, since in many cases sewage treatment plants could become energy self-sufficient because they used the energy from the bio-waste.
disadvantage
The use of kitchen waste shredders also results in a higher consumption of tap water. In areas in which the sewage treatment plants do not have primary treatment or digestion , shredded kitchen waste causes a considerable increase in the energy requirement in the aeration tank . This is especially true for smaller sewage treatment plants in rural areas.
Even in a sewage treatment plant with primary clarification and digestion, some of the shredded kitchen waste will go into solution and cannot be separated from the water in the primary clarification tank. These additional dissolved substances will trigger an increased need for oxygen and thus also energy in the aeration tank.
The accumulation of sewage sludge will increase considerably. Sewage sludge treatment has become very expensive at many plants, especially since in more and more areas the sludge can no longer be used for agricultural purposes.
The formation of additional deposits in the sewer network is also possible. In Germany around half of all sewer systems are still operated as a mixed system for rainwater and wastewater. As a result, in the event of heavy rain, the organic waste is discharged via the discharge systems into the receiving waters . In separation systems , there is this effect less.
The temporary ban on the discharge of kitchen waste into the sewer systems of American cities after the Second World War appeared to be based primarily on the described pollution of the receiving waters during heavy rain and the fear that the existing systems could be overloaded. After positive research results, lobbying work by device manufacturers and modernization of the sewer networks, the bans were lifted almost everywhere.
As a result of the ongoing trend towards reducing water consumption, problems arise in many sewer systems due to inadequate flushing, which can increase with increased entry of solid matter.
Rinsing out the shredded kitchen waste usually increases water consumption by an average of around 3 liters per person. The energy consumption of the device is around 3 to 4 kWh per year.
With the introduction of kitchen waste shredders, it is usually not possible to dispense with organic waste bins, as these are required, for example, to dispose of shrub cuttings and other waste that cannot be processed in the waste shredder.
The majority of the sinks installed in Germany are equipped with smaller drain openings than are necessary for installing a waste shredder. The assembly of the device then requires the replacement of the sink.
Individual evidence
- ↑ Shpiner, Ron. "The Effect of Domestic Garbage Grinding on Sewage Systems and Wastewater Treatment Plants". Submitted to the Senate of the Technion - Israel Institute of Technology, January 1997
- ↑ 66901 thousand from 132832 thousand = 50%. Source: Table Heating, Air Conditioning, and Appliances from the American Housing Survey 2013
- ↑ Erna Horn : The modern household, Kempten 1953, p. 320 u. Fig. On plate 53.
- ↑ (DIN) EN 12056-1, CEN (European Committee for Standardization), 1986 1 , 2001, Chapter 4, Paragraph 6, p. 5; therein also: "An EN has the status of a German standard ". Installation see p. 10
- ↑ Franz-Josef Heinrichs: New European drainage standard - What changes does it bring for the sanitary specialist? in IKZ-Haustechnik, edition 8/2001, p. 27 ff.
- ↑ DIN, Water Management Standards Committee, 1986-100: 2002-03, 6.5, Berlin 2002, p. 18
- ↑ Examples: The Weimar Drainage Statute , as of 2012, prohibits the discharge of shredded kitchen waste in Section 15, as does the Braunschweig Wastewater Statute , as of 2014, in Section 11. The Braunschweig statutes also prohibit the installation of "waste shredders" in Section 7 (13).
- ↑ SR 814.201 Water Protection Ordinance of October 28, 1998 (GSchV). Retrieved March 21, 2020 .
- ^ Austrian Water Law Act (WRG) - version of June 14, 2020
- ↑ Austrian General Waste Water Emissions Ordinance (AAEV) - version dated June 14, 2020
- ↑ Kitchen waste chopper. (PDF; 123 kB) "The use of these devices is prohibited". In: Water Management Styria. April 24, 2015 .
- ↑ Fricke, Goedecke, Einzmann: The Separate Collection and Recycling of Biowaste - Inventory 2003 ( page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. (PDF; 319 kB); In: “The future of the separate collection of organic waste”, series of publications by ANS 44, Orbitverlag, Weimar, pp. 11–64; Section 3.1.1
- ↑ Leo Hickman: Leo Hickman: Is it OK ... to use a food waste disposer | Money | The Guardian , Money.guardian.co.uk. August 21, 2006. Retrieved April 23, 2011.
- ↑ kompost.de: More than 6 million tons of bio-waste ( page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.
- ^ The Impact of Food Waste Disposers in Combined Sewer Areas of New York City (PDF) Retrieved April 23, 2011.
- ↑ MYRNA OLIVER: Robert Cox; Popularized Use of Garbage Disposers (en-US) . In: Los Angeles Times , June 24, 1999. Retrieved July 23, 2018.
- ↑ Michael Specter: Only in New York: Garbage Disposers, Banned, Stir Debate . In: New York Times . June 22, 1992. “Most major cities banned garbage disposers after World War II, driven by worries that ground food would clog sewer pipes beneath their booming neighborhoods. ... But a series of studies from universities and the not completely disinterested plumbing industry showed that the additional waste from ground food scraps would rarely harm a city sewage system. "
- ^ New York City Department of Environmental Protection. June 1997. "The Impact of Food Waste Disposers in Combined Sewer Areas of New York City".
- ^ Karlberg, Tina and Erik Norin. VA-FORSK REPORT, 1999-9. "Food Waste Disposers - Effects on Wastewater Treatment Plants. A Study from the Town of Surahammar".
