LITERATURE OVERVIEW
Impacts of Disposers
andFood Waste Management

Summary prepared by:Michael Keleman
Casey Furlong
Revised:December, 2020

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Table of Contents
1.0 Introduction ............................................................................................................................... 3
2.0 Food Waste Disposer Background............................................................................................ 4
2.1 Advantages ............................................................................................................................ 4
2.2 Disadvantages........................................................................................................................ 5
2.3 Disposer Specifications ......................................................................................................... 5
2.4 Food Waste Composition ...................................................................................................... 6
3.0 Food Waste Disposer Common Concerns ................................................................................ 7
3.1 Water Use .............................................................................................................................. 7
3.2 Electricity .............................................................................................................................. 8
3.3 Plumbing and Sewers ............................................................................................................ 9
3.4 Wastewater Treatment Plant Impacts .................................................................................. 12
3.4.1 Pollutant Loading ......................................................................................................... 12
3.4.2 Preliminary Treatment .................................................................................................. 14
3.4.3 Primary Treatment ........................................................................................................ 14
3.4.4 Secondary Treatment (Biological Treatment) .............................................................. 15
3.4.5 Anaerobic Digestion and Food Waste Energy Recovery ............................................. 16
3.4.6 Biosolids Handling and Disposal ................................................................................. 18
3.4.7 Effluent Characteristics ................................................................................................ 19
3.5 Fats, Oils, and Greases ....................................................................................................... 20
3.6 Septic Systems .................................................................................................................... 21
4.0 Alternative Management Comparisons................................................................................... 21
4.1 Landfills .............................................................................................................................. 22
4.2 Composting and Curbside Food Waste Collection ............................................................. 23
5.0 Life Cycle Analyses ................................................................................................................ 24
5.1 “Sustainable Food Waste Evaluation” ................................................................................ 24
5.2 “Life Cycle Assessment of Systems for the Management and Disposal of Food Waste” .. 25
5.3 “Life-Cycle Comparison of Five Engineered Systems for Managing Food Waste” .......... 26
5.4 “Assessment of Food Disposal Options in Multi-Unit Dwellings in Sydney” ................... 27
6.0 Research References ............................................................................................................... 29

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List of Acronyms
AD

Anaerobic Digestion

BNR

Biological Nutrient Removal

BOD

Biological Oxygen Demand

CO2eCarbon Dioxide Equivalent

COD

Chemical Oxygen Demand

CFWC

Curbside Food Waste Collection

FFA

Free Fatty Acid

FOG

Fats, Oils, and Greases

FW

Food Waste

FWD

Food Waste Disposer

GWP

Global Warming Potential

LCA

Life Cycle Analysis

MLE

Modified Ludzack-Ettinger

MRF

Material Recovery Facility

MSW

Municipal Solid Waste

rbCOD

Readily Biodegradable Chemical Oxygen DemandSP

Smog Potential

TKN

Total Kjeldahl Nitrogen

TN

Total Nitrogen

TSS

Total Suspended Solids

VS

Volatile Solids

VSS

Volatile Suspended Solids

WTE

Waste-to-Energy

WW

Wastewater

WWTP

Wastewater Treatment Plant

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1.0 Introduction
Food waste disposers were invented in the 1940’s, initially as a convenience for residential
kitchens and cooks. As interest developed in the post-WWII era’s housing boom, disposers were
thoroughly evaluated by municipalities to assess their efficacy with respect to local solid waste
and wastewater collection and treatment systems.
By the end of the 20th century, disposers had become a standard appliance, installed in the
majority of U.S. homes and nearly ubiquitous in new residential construction. The market forcommercial food waste disposers – in a variety of food-serving establishments, such as
restaurants, cafeterias, and markets – also has grown. International acceptance of food waste
disposers also is growing, in response to significant concerns about diverting organic food wastefrom landfills and increasing the beneficial use of food waste for land application. Everythingmunicipalities normally do with food waste is environmentally noxious: stored inside buildings(even refrigerated); piled in bags on sidewalks; collected in trucks; and shipped to distantlandfills, where it generates leachate and greenhouse gases. This process is not cheap, hygienic,
environmentally friendly, nor sustainable.
In sum, food waste disposers form an impressive part of an integrated modern waste
management system in many parts of the world.
This document reviews fifty (50) of the most recent studies and reports, three (3) executive
summaries, two (2) literature reviews, one (1) textbook, two (2) specifications and requirements,and one (1) internal calculation, for a total of fifty-nine (59) research references. All informationin this document was conducted by universities, research institutions, and government agencies
across the United States and in many countries that examine the efficacy of food waste disposers.
It compiles the findings regarding all facets of the sewage collection, treatment, and disposal
process and organizes the information according to major concerns and assumptions regarding
garbage disposers. In sum, these studies have largely determined that the impacts of disposers
are manageable, and that disposers provide a significant set of environmental benefits that merits
their acceptance and use in conjunction with (rather than in competition to) other alternatives todivert organic waste from landfills.

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2.0 Food Waste Disposer Background
2.1 Advantages
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Removing kitchen waste from compost produces cleaner and better compost [de Koning,2004].
Reduced transportation noise [de Koning, 2004].
Reduced space concerns for food waste storage [de Koning, 2004].
Renewable energy value of Wastewater Treatment Plant (WWTP) anaerobic digestion
biogas [de Koning, 2004][Hernandez, 2002, “Los Angeles Digesters”][Karlberg,
1999][Karrman, 2001][Kegebein, 2001][Rosenwinkel, 2001][Shpiner, 1997].
Reduced incidence of disease-causing vector attraction in comparison to food waste
storage/collection [de Koning, 2004][Diggelman, 1998][Shpiner, 1997][Terpstra, 1995].
Reduced truck collection, which blocks narrow streets [de Koning, 2004][Kegebein,
2001].
Natural selector of organic wastes, whereas, composting relies on the education andgoodwill of the participants [CECED, 2003].
Reduces the potential of uncontrolled biochemical processes in landfills (i.e., leachate
treatment) [Rosenwinkel, 2001].
Reduced transportation emissions and costs [Karlberg, 1999][Karrman, 2001][Kegebein,
2001].
High carbon content of food waste improves the overall WWTP nitrogen and phosphorus
nutrient removal process [Diggelman, 1998][Kegebein, 2001][Rosenwinkel, 2001][Kim,2019].
Improved hygienic environment in comparison to food waste storage/collection[Kegebein, 2001][Rosenwinkel, 2001][Shpiner, 1997]Terpstra, 1995].
Healthier Municipal Solid Waste (MSW) working environment [Karlberg, 1999].
Less expensive and complicated than source-sorting food wastes [Karlberg, 1999].
Reduced MSW garbage collection amount and frequency [Diggelman, 1998][New York
City Department of Environmental Protection, Executive Summary, 1997][New York
City Department of Environmental Protection, 1997][Shpiner, 1997].
Promotes nutrient recycling from organic wastes when WWTP biosolids are land-applied[Diggelman, 1998].
Environmentally friendly and sustainable food waste disposal option [Diggelman, 1998].
As food waste is 70% water, the WWTP is a more natural system of waste processing
than hauling the waste to a “solid waste” facility [Diggelman, 1998].
As food waste is 70% water, the WWTP system reduces leachate diverted from landfill
and compost systems, which reduces potential contamination to groundwater[Diggelman, 1998].
Most convenient and likely-used source selector of organic kitchen wastes [Diggelman,
1998].
As food waste is 70% water, the WWTP system anaerobic digestion process will produce
a viable energy source, whereas, incineration offers a very small net energy gain that also
produces contaminated emissions requiring additional treatment [Diggelman, 1998].

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As food waste is 70% water, the WWTP system is a more natural method of waste
processing than composting, which, although enhanced by the additional moisture, does
require stricter operational control to avoid anaerobic conditions, and results in the loss ofmost nutrients to the extent that the final product is of low value [Diggelman, 1998].
Ease of use [Shpiner, 1997].
WWTPs are equipped to treat food waste due to high water and organic content [Shpiner,
1997].

2.2 Disadvantages
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Increased potential loadings impact on combined sewer overflows [Rosenwinkel, 2001].
Increased water consumption [Rosenwinkel, 2001].
Increased energy consumption for both disposer use and WWTP aeration [Rosenwinkel,
2001].
High initial costs for the user (not the municipality) [CRC, 2000][Diggelman,
1998][Karrman, 2001][Rosenwinkel, 2001].
Potential grease/solids build-up in the sewer collection system, which increases
maintenance costs [Kegebein, 2001][ New York City Department of Environmental
Protection, Executive Summary, 1997][ New York City Department of Environmental
Protection, 1997].
Increased WWTP biosolids generation and disposal costs [de Koning, 1996][Karrman,
2001][ Rosenwinkel, 2001][Shpiner, 1997][Terpstra, 1995].
Increased loadings of BOD and TSS to the WWTP [Shpiner, 1997].

2.3 Disposer Specifications

Association of Home Appliance Manufacturers (AHAM) provided testing specifications
to test for the criteria in the ASSE Standard #1008 in a systematic way [AHAM, 2009].
Sink mounted food waste disposer units should be designed to fit a sink with a 3.5 inch
(89 mm) nominal drain opening (this is the normal drain opening size to which sinks aredesigned) [AHAM, 2009, p. 2].
Residential Disposer Specifications as set by ASSE International [ASSE, 2006]
o Discharge not less than 6.0 GPM (0.36 L/s) at a head of 10.0 inches (254.0 mm)[ASSE, 2006, p. 3].
o Terminal outlet shall be 1.5 inches (40 mm) nominal tube size [ASSE, 2006, p. 1].
o Ground product retained on the sieve should not weigh more than 1.0 ounces (28grams) [ASSE, 2006, p. 4].
o Particles on the inside of the FWD shall not exceed 0.25 inches (6.7 mm) [ASSE,
2006, p. 5].
o For FWDs with a dishwasher connection, the water level shall not rise more than
1.0 inch (25.4 mm) above the water level in the sink [ASSE, 2006, p. 5].
o For FWDs without a dishwasher connection, the water level shall not rise above
the sink mounting flange to any degree [ASSE, 2006, p. 5].
o There shall be no evidence of leakage during or after the cycle of running theFWD [ASSE, 2006, p. 6].

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Disposers have a 600W electric motor, used on average 2.4 times/day and 30 seconds
each time [Karrman, 2001].
Approximately 98% of all particles pass through a 2 mm sieve [Kegebein, 2001].
The food waste disposer can be described as a mill rather than a cutter. It works with arotary disk in which two hammer-cheeks mobile in horizontal direction are fastened. The
disk is provided with 5 mm holes. In opposition to frequently heard prejudices, a disposer
does not contain rotating knives [Rosenwinkel, 2001].
Non-food wastes cannot be ground since the attempt will cause a resistance, which if it
becomes excessive, will cause the resistor to switch off [Rosenwinkel, 2001].
A 1400 rpm rotating disk with a number of 3-4 mm holes [Karlberg, 1999].
The energy requirement for use is 3-4 kW-h//household/yr [Karlberg, 1999].
A Japanese study found food waste particle dispersion between 2-5 mm [Karlberg, 1999].
A grinding distribution of heaviest components show 62% of particles are <1.7 mm, 86%
are <2.83 mm, and 94% are <3.36 mm [Shpiner, 1997].

2.4 Food Waste Composition
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Food Waste Composition varies depending on the culture and diets of the local
community. Therefore, it is difficult to define a uniform composition of food waste. In
some studies a “standard diet” is created in order to study local food waste compositions[Kim, 2015, p. 62].
Since the COD/N and BOD/N ratios (63 and 27, respectively) were higher than theparticulate ratios (42 and 22, respectively), this suggests that the non-settleable fraction(aqueous phase) can enhance the denitrification process and impact secondary aeration[Kim, 2015, p. 69].
Considering 50 grinded food waste samples, the relative mass ratios of COD: BOD5:
TSS: TN: TP: dry food waste was 1.21: 0.58: 0.36: 0.025: 0.013: 1 [Nakhla, 2014, p. 11].
Assuming wet food waste consists of 30% dry waste and 70% water, dry food waste isdefined by the following chemical formula: C21.53H34.21O12.66N1.00S0.07 [PE Americas,
2011, p. 19].
Assuming wet food waste is 30% dry waste and 70% water and 95% of the dry foodwaste is VS with the remaining 5% being inert, then 100kg of wet food waste would
equate to a dry food waste of 44 kg COD with a 1.54 kg COD/kg dry food waste ratio
applied [PE Americas, 2011, p. 19].
For 30 kg of dry food waste, 17 kg is TSS while the remaining 13 kg is soluble and isremoved during biological treatment [PE Americas, 2011, p. 20].
The impact of FWDs depends on the food waste composition, which depends on the typeof food waste [Thomas, 2010, p. 6].
Daily person equivalent contributions due to organic food waste through disposers is 75
g/person/day for Chemical Oxygen Demand (COD), 50 g/person/day for Total
Suspended Solids (TSS), 2.5 g/person/day for Total Kjeldahl Nitrogen (TKN), and 0.25
g/person/day for Total Phosphorus (P). This equates to a COD/TKN ratio of 30[Bolzonella, 2003].
Typical organic waste composition is 25.6% TS (74.4% water), 96.5% VS, 3.2% TKN,
0.2% P, and 1,200 mg/L COD [Bolzonella, 2003].

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Grindable food waste is about 35% of total household waste, which equates to 235
g/person/day (85 kg/person/yr.) [CECED, 2003].
Airport food waste sample analysis results were moisture 72.9%, Total Solids (TS)27.1%, and Volatile Solids (VS) 94.9% [Hernandez, 2002, “Los Angeles Digesters”].
Generated food waste is 76 kg/person/yr., with 67% able to be ground through a disposer(i.e., 50.9 kg/person/yr.) [Karrman, 2001].
Food waste generation is about 40-60 kg wet/person/yr. [Kegebein, 2001].
Average food waste generation is 182 kg/household/yr. or 0.24 kg/person/day [CRC,2000].
Lagerkvist & Karlson, 1983 and Nilsson et al, 1990 both indicate that about 20% of foodwaste suitable for composting is not suitable for disposer grinding [Karlberg, 1999].
Olsson & Retzner, 1998 indicates that 75 kg/person/yr. of food waste are generated[Karlberg, 1999].
De Koning & Van der Graaf, 1996 assume that the total amount of food waste that can beground through a disposer is 44 kg/person/yr. [Karlberg, 1999].
Nilsson et al, 1990 state that about 75% of food waste Biochemical Oxygen Demand(BOD) is in particle form and 25% in dissolved form [Karlberg, 1999].
The average person generates 0.29 lb./day of food waste with 0.21 lb./day (75%) able tobe processed through a disposer [Diggelman, 1998].
Food waste is 70% water and 30% solids [Diggelman, 1998].

Table 1 – Waste Compositions. Typical Food and Human Waste Compositions [Diggelman,
1998].
Waste Compositions
Type
C
H
O
N
S
Food Waste
50.5%
6.72%
39.6%
2.74%
0.44%
Human Waste
59.7%
9.5%
23.8%
7.0%
0%
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Food waste is 64.3% water (35.7% solids) with 75.5 g/person/day generated through adisposer [Shpiner, 1997].
Food waste moisture content is 60% with a production of 0.08 wet kg/person/day (0.048
dry kg/person/day) [de Koning, 1996].
Average household food waste disposal is 260 g/person/day [Terpstra, 1995].
Food waste is 30% dry solids (70% water) [Terpstra, 1995].

3.0 Food Waste Disposer Common Concerns
3.1 Water UseDisposers account for only about 1% of a household's daily use of water [Nakhla, 2014,
P. 6].
Estimate 1 gal/capita/day with disposer use [Nakhla, 2014, p. 6] [ New York City
Department of Environmental Protection, Executive Summary, 1997].
Disposer water usage is 3-6 L/household/day [Karlberg, 2012].
After installation of FWDs, the extra water consumption was marginal (less than 2%increase in water use) [Clauson-Kaas, 2011, p. 6].

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DeOreo et al, 2011 found that residential disposers save 13 gallons ofwater/household/day [DeOreo, 2011, p. 205].
Based on grinding food waste in the laboratory, the water usage per capita added after theuse of FWD increases only 4.45%, and the utility fee is only 0.02 Chinese Yuan (CNY)(per capita per day) [Tongji University, 2010, p. 59].
The change in water use from FWDs is trivial [Evans, 2007, p. 23].
After the introduction of FWDs, no water consumption changes were noticed [Imanishi,
2005, p. 14]. [Yoshida, “Impacts of Food Waste Disposers”].
The use of disposers does not result in a noticeable increase in the volume of wastewater[de Koning, 1996].
Nilsson et al, 1990 estimate that water consumption does not change because of disposeruse [Karlberg, 1999].
Increased water demand from disposers is 0.02% at 3% market penetration, and 0.24% at
38% market penetration (assuming a 1% disposer market growth per year). Therefore, nosignificant impacts on the city water supply from disposers are expected [New York City
Department of Environmental Protection, Executive Summary, 1997].
There is no statistical evidence that city water consumption has changed since theinstallation of disposers [New York City Department of Environmental Protection, 1997].

Table 2 – Water Consumption Rates. FWD Water Consumption Rates (L/person/day).
FWD Water Consumption Rate
Source(L/person/day)Clauson-Kaas, 2011, p. 6
3-6
CECED, 2003
3-4.5
Kegebein, 2001
3-4.5
Cooperative Research Centre, 2000
2.95
Shpiner, 1997
1.01
de Koning, 1996
4.5
Terpstra, 1995
4.48
Waste Management Research Unit, 1994
4
Average
3.99 (1.05 gallons/person/day)
3.2 ElectricityAssuming a FWD is used for 30 seconds per person daily with a power draw of 1000 W,
the estimated power consumption for FWDs is 0.008 kWh/capita/day [Leverenz, 2013, p.
11].
The power consumption for FWD is 0.119 kWh/capita/day, which equals a utility fee of
0.073 CNY/capita/day considering 0.617 CNY/kWh in Shanghai [Tongji University,
2010, p. 60].
With electricity being roughly $0.10 per kilowatt-hour and a disposer using 2.3 uses per
day with each use running for 30 seconds while the average disposer uses 500 watts
while in use, the average cost is about $0.35 per year [Strutz, 2005].
The Plumbing Foundation City of New York, 2001 indicates that using the upper time
limit for disposer usage of 2 min/day and the most common 0.5 hp motor, the disposer
consumes less than a 75W light bulb uses in 10 minutes [Marashlian, 2004].

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Table 3 – FWD Energy Consumption Estimates and Price Estimates. Prices were calculated
based on the average cost of electricity estimated at $0.10 per KWh. The energy consumption
estimates range from less than 3 to 6 KWh/home/year, which is small in comparison to theaverage household energy consumption.
SourceLeverenz, 2013
PE Americas, 2011
Tendaj, 2008, p. 11
Evans, 2007
Balzonella, 2003
Waste Management Research
Unit, 1994
Average

FWD Energy Consumption
Estimate (KWh/home/year)
4
4
5-6
2-3
4.3

Price
(US$ per home per year)
$0.40
$0.40
$0.60
$0.30
$0.43

<3

$0.30

4.1

$0.41

3.3 Plumbing and Sewers
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Most food particles discharged from disposers are between 2mm and 4mm with aunimodal range of distribution [Nichols, 2019, p. 3].
Settling velocity is always less than 0.1 m/sec, except for eggshells, which had maximum
fall velocities of 0.13 m/sec [Nichols, 2019, p. 3].
A study of 181 concrete pipes serving single family households comparing FWD usage
with sewers revealed that FWDs have an impact on the use of sewers, but the majority ofdeposits were small, indicating that the impact of FWDs on sewer performance is minor[Mattsson, 2014, p. 1].
The long-term impacts of FWDs on small diameter sewer systems of residential areas
were shown to be minor [Mattsson, 2014, p. 1].
More troubles aroused in sewers when households used food waste that was notcompatible with FWDs, such as eggshells, which suggests the importance of proper
education and use of FWDs [Mattson, 2014, p. 9].
Many of the problems observed with the use of FWDs and sewers/plumbing could be
avoided by having pipes with a steep inclination [Mattsson, 2014, p. 8].
Deposits in pipes with large inclinations could be caused by sags in the pipes [Mattsson,
2014, p. 8].
In a nine month study in PuDong, the use of FWDs did not result in sewer blockages orsedimentation [Tongji University, 2013].
Long term impacts on sewer degradation is unknown. The Sustainable Food Waste
Evaluation assumes a 5% aerobic and 10% anaerobic degradation [WERF, 2012, p. A31].
Processing food waste will not increase sedimentation and blockages since the density ofground food waste usually has a lower specific density than waste water [Clauson-Kaas,
2011, p. 57].
The PE Americas LCA assumes a negligible (0%) degradation [PE Americas, 2011, p.
113].

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The FWDs effect on the sewer system will be small [Tendaj, 2008, p. 40].
Nilsson et al, 1990 showed that a stimulated optimal usage of disposers for 15 years did
not exhibit operational problems within the plumbing system. Regular inspection andvideotaping of the piping system found a buildup of sewage was reported at water levelwith a width of 2-3 cm along the envelope surface at a thickness of 0.5-1.5 cm[Marashlian, 2004].
Some trouble could arise from increased O&G discharge in sewers. However, studies
have shown that no problems were caused [Bolzonella, 2003].
Sewage velocity is sufficient enough to maintain sewers clean. Generally, self-cleansing
velocity is in the range of 0.5-1.6 m/s for sewers with a diameter of 200-2000 mm[Bolzonella, 2003].
Study results revealed that only 16.8% of TS (from ground organic wastes) settled in
sewers, whereas, the residual 83.2% reached the WWTP. Therefore, sewers should beconsidered a feasible way to transport food waste [Bolzonella, 2003].
Another aspect to consider is to avoid disposer installations in areas where blockages orhydrogen sulfide formation already are problems in the sewage system [Karrman, 2001].
A daily minimum flow velocity of 0.5 m/s is seen as sufficient for food waste transport
free of sedimentation. The density and settling velocities of food waste particles is verymuch less in comparison to mineral particles [Kegebein, 2001].
Increased costs in sewer maintenance (from disposers) cannot be ruled out. At 100%
market penetration, a 20% increase could result [Kegebein, 2001].
At a 50% market share, disposers contribute <0.1% flow to instantaneous maximum flow
in sewer systems [CRC, 2000].
At a 50% market share, disposers increase hydrogen sulfide generation in the seweragesystem by 30% [CRC, 2000].
Up to a 15% market penetration, the use of disposers in multi-unit dwellings would havea small impact on sewage collection systems [CRC, 2000].
About 91% of solids in disposer effluent are <1 mm (0.25 in) in size, therefore, this small
size would be unlikely to clog or become deposited in sewers or plumbing pipes [CRC,2000].
De Koning and Van der Graaf, 1996 state that the concern over grease and fats (fromdisposers) clogging sewers is invalid because the use of cold water causes grease and fat
to congeal and attach to other food waste solids [CRC, 2000].
There does not appear to be any sound evidence in literature to suggest that disposers
cause clogging or deposits of solids in pipes [CRC, 2000].
In a 1993 apartment disposer use study, sewer pipes were flushed and videotaped with nodifferences observed (i.e., no additional particle, sludge, or grease accumulation) after
both 1 and 3 years following installation [Karlberg, 1999].
Disposers may cause increases in TSS and Oil & Grease (O&G) in the sewer system.
There may be an increase in sewer maintenance costs estimated at 0.61% at a 3% market
penetration and 7.6% at a 38% market penetration (assume 1% market penetration peryear) [New York City Department of Environmental Protection, 1997].
In combined sewer systems built with an adequate self-cleaning velocity (ex., sanitary
sewers 2.0-2.5 ft./sec or about 0.61-0.76 m/s and storm sewers 2.5-3.0 ft./sec), no
additional deposits are expected due to ground food waste since its specific gravity of
1.01 is less than that of sewage (1.05), and much less than the suspended solids carried by

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storm runoff (specific gravity 2.65) [New York City Department of Environmental
Protection, 1997].
In combined sewer systems, the introduction of disposers will cause increases insuspended solids of about 20% on a per capita basis, and expected to increase O&G
discharges. As a result, combined sewer systems with insufficient self-cleaning velocities
will require routine cleaning, which will increase maintenance costs [New York City
Department of Environmental Protection, 1997].
Videotaping done before and after the study detected no noticeable deposits of solids
build-up. Therefore, no potential significant adverse impacts on the sewer system are
expected from disposer use [New York City Department of Environmental Protection,
Executive Summary, 1997].
Wicke, 1987 states that a concentration of less than 1% solids (10,000 mg/L) will notcause an increase in solid sedimentation, or for every 12 gal of water (45 L) there should
be no more than 1 lb. (454 g) of ground garbage [Shpiner, 1997].
There is no literature example to prove that the use of disposers causes clogging ordeposits in sewers. Most food solids have a density about equal to water and are easilysuspended in water. Thus, it is unlikely that ground food waste contributes to sewer
clogging [de Koning, 1996].
Discharged with cold water, any grease or fat found in food waste will congeal and attach
itself to the other ground waste particles. Running cold water will prevent coating of thesewer with grease [de Koning, 1996].
Disposers pose negligible impacts on water and wastewater infrastructure [Jones, 1990, p.
14].

Table 4 – Cleaning Velocity. Cleaning Velocities/Minimum Flow Velocities
Cleaning Velocity/Minimum Flow Velocity
Source(m/s)
Evans, 2007
0.48-0.9
Bolzonella, 2003
0.5-1.6
Kegebein, 2001
0.5
New York City Department of Environmental
0.61-0.76
Protection, 1997
Average
0.94

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3.4 Wastewater Treatment Plant Impacts
3.4.1 Pollutant LoadingFigures 1-3 show estimated loading increases in TSS, COD, BOD, oil and grease,potassium, total P, inorganic P, organic P, TKN, organic N, and NH3.

Figure 1 – Estimated Loading Increase from Disposers (TSS, COD, and BOD) [Metcalf, 2014]

Figure 2 – Estimated Loading Increase from Disposers [Metcalf, 2014]

Figure 3 -- Estimated Percent Increase in Loading from Disposers [Metcalf, 2014]

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The experimentally determined COD and BOD of food wastes were 22% lower than thetheoretical values, suggesting that the impact of food wastes on the WWTP is lower thanoriginally supposed [Nakhla, 2014, p. 11].
Installing FWDs will not affect hydraulic load of the WWTP [Clauson-Kaas, 2011, p.
58].
WWTPs are designed to treat biodegradable material suspended in water, i.e. similar tothe output of FWD [Evans, 2007, p. 4].
Additional pollutant loading due to disposer use is 66 g/person/day BOD, 60
g/person/day TSS, 2.1 g/person/day TKN, 0.3 g/person/day P, and 2.5-5% biosolids [deKoning, 2004].
The effect of disposers on WWTP processes is very limited [de Koning, 2004].
At a 15-20% disposer market share, loadings do not result in significant variations in thecharacteristics of sewage. At a 20-35% disposer market share, an increased WWTP
system energy consumption is observed due to greater respiration of the active biomass
and a larger production of excess biosolids. Beyond a 35-40% disposer market share,
additional works must be done at the WWTP. European Union (EU) market levels will
not exceed 15% in 25-30 years, thus, normal WWTP upgrades will allow for an
accommodation of increased disposer loading [CECED, 2003].
Disposer discharge to a WWTP equates to 73 g/person/day dry matter, 25 g/person/day
BOD, 0.25 g/person/day phosphorus, and 1.3 g/person/day nitrogen [Karrman, 2001].
At 100% disposer market share, additional loadings from disposers are 3-5% for flow, 510% for screenings, 5% for grit, 10-25% for BOD, 40-60% for TSS, 5-10% for TKN, 714% for P, 50-70% for primary sludge, 10-40% for waste activated sludge, 30-50% fordigested sludge, and 90-100% for biogas [Rosenwinkel, 2001].
The additional loads for wastewater treatment and sludge digestion can be estimated very
well and, due to slow market penetration, will not lead to uncontrolled overloading to the
WWTP “overnight” [Rosenwinkel, 2001].
At a 50% disposer market share, increases in sewage flows are very small (additional
0.5% to the mean average daily flow) [CRC, 2000].
At a 15% disposer market share, no operational problems should be caused in terms of
BOD, TSS, or O&G loadings [CRC, 2000].
Up to a 15% disposer market share, the use of disposers in multi-unit dwellings would
have a small impact on sewage treatment systems. Beyond this figure are increasing
impacts, with potentially significant impacts at a 50% market share. However, this levelof market share is unlikely in the near future [CRC, 2000].
No operational problems are expected for market levels up to 15% in regard to BOD andO&G loadings, or up to 20% market for additional TSS loadings [CRC, 2000].
Up to a 50% disposer market share, the transport and treatment of disposer effluent
would require an additional 0.5% energy, and total WWTP costs would increase 0.5%
[CRC, 2000].
Up to a 50% disposer market share, additional loadings from disposers are <1% for TSS
and nutrients, and <2% for BOD [CRC, 2000].
At a 100% disposer market share, flows would increase 0.4%, biosolids production
would increase 18.1%, BOD would increase 16.5%, and nutrients would increase 3.0%
for TKN and 4.6% for P [Waste Management Research Unit, 1994].

14
3.4.2 Preliminary Treatment






Using FWD to divert food waste results in a waste stream that is fairly free fromcontaminants and debris, so it is not subject to additional processing, cleaning, andpreliminary treatment at the WWTP [Leverenz, 2013, p. 10].
It is expected that food waste will contain no grit [Hernandez, 2002, “Hyperion Digestion
Pilot Program”].
With disposer usage, WWTP screens and grit chambers will only be affected to a small
extent [Rosenwinkel, 2001].
Screenings are not expected to be added by food waste disposers [New York City
Department of Environmental Protection, 1997].
Grit was assumed to be 5% of TSS. A method to evaluate scum or grit production impact
could not be determined [New York City Department of Environmental Protection,
1997].

3.4.3 Primary Treatment


Fractionation of food waste was 40% soluble, 0% colloidal, 60% particulate of the total
COD; N and P were predominantly in the particulate form; settling over 3 hours removes
59-62% of TSS, 46-53% of BOD5, and 49-56% of COD [Chowdhury, 2016, p. 664].
The large particulate fraction of FW tends to be removed in primary sedimentation while
the soluble fraction of FW in primary effluent can be utilized for nutrient removal [Kim,2015, p. 68].

Table 5 – Particulate Fractions. Particulate Fractions in 50 grinded food waste samples [Kim,2015, p. 69]
Parameter
Particulate Fraction
COD
58%
BOD5
67%
TN
74%
TP
100%
Table 6 – Percent Removal. Removal percentages of TSS, BOD5, and COD after a 3 hour (180minute) time period [Nakhla, 2014, p. 11]
Percent Removal
Parameter
after 3 hours
TSS
59-62%
BOD5
46-53%
COD
49-56%


During primary sedimentation, 80% of the solids and 90% of ground food waste areremoved [PE Americas, 2011, p. 26].
FWD use increases COD and TSS by 12% and 24% respectively, still in the allowable
range for municipal sewers [Tongji University, 2013].

15






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

The use of FWDs increases the COD in the sewage, as well as the C/N and C/P ratios,
therefore sewage treatment will benefit with improved biological nitrogen andphosphorus removal [Tongji University, 2013].
Thomas’s study in 2010 noted that when the food waste settled in buckets (in order tosimulate primary clarification), the results indicated roughly 62% TP and 90% ammonia
were in the supernatant while 77% and 90% of the TSS and RSS were in the sediment
fractions [Thomas, 2010, p. 7].
Battistoni, 2007 did not find any solid sedimentation [Battistoni, 2007, p. 896].
Primary settling food waste removal is 20% BOD, 90% TSS, 5% TKN, and 10% P [deKoning, 2004].
The average settling velocity of food waste is 13.2 m/hr. (43.3 ft./hr.) [Bolzonella, 2003].
According to lab experiments, 75% (of disposer food waste) is assumed to be settled in
the pre-sedimentation step [Karrman, 2001].
With disposer usage, most of the particulate food waste fraction will settle in the WWTP
primary clarifier [Rosenwinkel, 2001].
Disposer solids settle readily under gravity. Sinclair Knight, 1990 state that the additionof disposer solids enhances the settling characteristics of sewage [CRC, 2000].
The portion of BOD from disposer use that does not settle in primary treatment wasdetermined using filtrate BOD. The portion of BOD from food waste that settled was
68.7% [New York City Department of Environmental Protection, 1997].
According to literature, over 90% of food waste is removed in primary sedimentation[Shpiner, 1997].
Brillet et al., 1986 reported that sedimentation removed 80% BOD and 90% TSS from
disposer waste [Shpiner, 1997].
Nilsson et al, 1990 reported that 75% of TS in wastewater and 90% of solids from
disposer grinding are removed in primary sedimentation, thus, overall removal is 80%[Shpiner, 1997].
Normal wastewater TSS removal is 58-64% and the food waste mixture TSS removal is78-86% [Shpiner, 1997].
The majority of additional BOD/COD and nutrient from disposer loading is concentrated
in settled primary sludge [de Koning, 1996].

3.4.4 Secondary Treatment (Biological Treatment)The additional soluble food waste fraction will lead to higher BOD/COD loading within
the biological treatment steps, which on one hand will cause a higher oxygen demand, buton the other can serve as a cheap and continuously available carbon source (for nutrient
reduction). A basic condition for the appropriate biological nitrogen and phosphorus
removal is a sufficient supply of easily degradable substrate (i.e., carbon) [Rosenwinkel,
2001].
At a 25% disposer market share, influent BOD would increase 12%, TKN and P would
increase 2% [Karlberg, 1999].
After a decade of city-wide disposer distribution, costs would increase $4.1M for themost expensive N-control measure (a 0.27% increase). This represents a de minimis

16




impact [New York City Department of Environmental Protection, Executive Summary,1997].
Brillet et al., 1986 reported that at a 100% disposer market share, biological treatment
loading increased 9.5-16% BOD and 7.5-10% TSS [Shpiner, 1997].
Increased loading to the biological processes from disposer usage is negligible (at 10%
market share) [de Koning, 1996].

3.4.5 Anaerobic Digestion and Food Waste Energy RecoveryFood waste sent to plants with AD and biological nutrient removal results in a net energy
gain, lower nitrogen and phosphorus in treated effluent, and lower overall costs fortreatment [Kim, 2019, p. 358].
The efficiency of converting the potential chemical energy contained in food waste toelectrical energy is estimated to be about 20% [Leverenz, 2013, p. 17].
Typical observed values for biogas yield from various food waste digestion studies are
157 and 600 m3/MT for a wet and dry basis, respectively [Leverenz, 2013, p. 18].
The power generated from biogas is derived to be approximately 80 kWhe/d [Leverenz,
2013, p. 37].

Figure 4 –Change in Energy. Change in Energy in three different wastewater treatment
processes at 50 and 100% disposer usage [Leverenz, 2013].

17




In a comparison of five studies regarding anaerobic digestion, four found an increase inproduction of biogas and one study found that BNR was enhanced as the carbon to
nutrients ratio increased after FWD were introduced [LGA, 2012, p. 23].
Upon reviewing 82 studies regarding end of life management methods for source
separated organics, it was found that anaerobic digestion and aerobic composting have alower climate impact than waste-to-energy and landfilling [Morris, 2012, p. 6].
The town of Surahammar, Sweden had a 0-50% increase in market penetration rate in aten year period. Digesters produced 46% more biogas after FWDs were installed [Evans,
2010, p. 1].

Table 7 – Added Sludge, Biogas, and Electricity. Various penetration rates’ effects on sludge
volume, biogas volume, and electricity gain [Tongji University, 2010].
Added Sludge
Added Biogas
Electricity Gain
Penetration Rate
Volume (t/d, 80%
Volume (m3/d)(kWh/day)water content)
1%
18
493
68
5%
91
2465
4437
10%
182
4930
8875
100%
1818
49304
88748
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





At a disposer market share of 10%, biogas production increased about 3% [Tendaj, 2008,
p. 40].
Biogas production from food waste is 1.15 m3/day of digested organics with a content of
22,000 kJ/m3 of biogas [de Koning, 2004].
The use of disposers will increase electric self-supply from 72% (at 0% disposer market
share) to 82% (at 10% market share). Profits gained in electrical supply will cancel out
additional biosolids treatment costs [de Koning, 2004].
Food waste (with 90% settling in primary treatment sludge) contains a high percentage ofeasily digestible organics (i.e., 80% VS) [de Koning, 2004].
The potential energy value from food waste by anaerobic digestion was assumed
insignificant [Marashlian, 2004].
At a 60% disposer market share, an increase of additional energy potential due toanaerobic digestion in the range of 54-73% was observed [Bolzonella, 2003].
Food waste Volatile Solids Destruction (VSD) is 83.7% (for thermophilic digestion at
55°C and food waste fruit and vegetables ground to a slurry) [Hernandez, 2002,“Hyperion Advanced Digestion Pilot Program”]
The optimum digester operating temperature was found to be 55°C and 57°C
(thermophilic digestion). As the temperature increased from that point, VSD and gas
production decreased and volatile acids increased [Hernandez, 2002, “Los Angeles
Digesters”].
The value of the biogas produced from food waste anaerobic digestion appears to exceed
the cost of processing the food waste and disposing of the residual biosolids (based on a
LAX Airport proposal to divert 8,000 tons/year of bulk food waste) [Hernandez, 2002,“Los Angeles Digesters”].
Methane gas generated in the anaerobic digesters is transported to a city-owned power
generation steam plant, which is used as a supplemental fuel and burned in the production

18

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




of steam and electrical energy (15 scf of digester gas produced per lb. of VS destroyed).
In digesting fruits and vegetables only, the value of the biogas appears to exceed the costof processing the food waste and disposing of the biosolids [Hernandez, 2002, “LosAngeles Digesters”].
The food waste disposer system generates more energy than consumed through thedigestion (biogas) [Karrman, 2001].
Food waste fermentation (anaerobic digestion) has an energy potential of 300
MJ/person/yr., which contributes about 25 kW-h/person/yr. to electric supply (about theelectrical usage of 1 WWTP) [Kegebein, 2001].
As most of the food waste from disposers settles in the WWTP primary clarifier, themajority will reach the anaerobic digester and cause an increase in biogas production anda regenerative energy source [Rosenwinkel, 2001].
Diverting food waste through a disposer to a WWTP should be encouraged when solids
handling systems are adequate, methane is combusted (through anaerobic digestion) to
produce energy, and effluent and/or sludge (biosolids) are returned to soil. Food waste iseffectively being recycled [Diggelman, 1998].
Additional gas production is generated from the volatile portion of food waste loading (7ft3 of gas is produced per lb. of VS that enter the digester) [New York City Department ofEnvironmental Protection, 1997].
Anaerobic digester gas production averaged 346 m3/day before disposer usage and 417
m3/day after disposer usage for an increase of 20.2% (at 65% methane, this equates to160,000 kW-h/yr.) [de Koning, 1996].

3.4.6

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




Biosolids Handling and Disposal

Biosolids have a chemical formula: C5H7NO2 with a carbon content of 53.1% and anitrogen content of 12.4% by mass [PE Americas, 2011, p. 30].
For every 100 kg wet food waste, there are approximately 7.3 kg biosolids for theconventional treatment with anaerobic digestion[PE Americas, 2011, p. 30].
Concerns about increased biosolids generation persist, and its potential environmental
and economic implications may differ with location [Marashlian, 2004].
Disposer usage showed minimal to no impact on the WWTPs total biosolids production
and handling processes as the high VSD from food waste yielded a minimum amount ofsolids in the residue [Hernandez, 2002, “Hyperion Advanced Digestion Pilot Program”].
Bench-scale jar testing showed food waste dewaters easily and used less polymer than
primary sludge/thickened waste activated sludge [Hernandez, 2002, “Hyperion Advanced
Digestion Pilot Program”].
Food waste appears to possess a natural settling capability [Hernandez, 2002, “LosAngeles Digesters”].
Before disposers are installed in large scale a long-term solution for the use of sludge
should be agreed, because disposers will increase sludge production [Karrman, 2001].
It is unlikely that biosolids produced by disposer usage would affect the contaminantlevel or reuse options of biosolids [CRC, 2000].
Ground food waste will significantly increase the quantity of biosolids, however, Nilsson
et al, 1990 notes that these biosolids will decompose easier than regular wastewaterbiosolids and more gas can be produced [Shpiner, 1997].

19
Table 8 – Disposer Market Share Effects. Various sources reporting on effects at certain
disposer market share values are presented.
SourceDisposer Market Share
EffectSolids to thickeners andde Koning, 199610%
digesters increase of 5%
Terpstra, 1995
10%5% more biosolids
No adverse effects to solids
CRC, 2000
25%
processing
Karlberg, 1999
25%
Sludge volume increase of 4%
Sludge increase is 7.2%, aKarrman, 2001
50%
10% increase compared to no
FWD useTerpstra, 1995
100%
50% more biosolids
3.4.7 Effluent CharacteristicsThe soluble and colloidal fraction of food waste that passes through primary treatment
has a positive impact on the removal of nitrogen and phosphorus from wastewater[Leverenz, 2013, p. 6].
The effluent total N was determined to range from 8.9 to 13.0 mg/L, decreasing as thepercent of FWDs in use increased [Leverenz, 2013, p. 25].
The effluent total Phosphorus was determined to be around 6.7-7.0 mg/L, decreasing as
the amount of FWDs in use reached 100 percent [Leverenz, 2013, p. 25].
Compared to no FWD usage, FWD usage can increase TN removal by 7 to 12 percent forthe biological nutrient removal (BNR) process with 50 and 100 percent FWD usage,
respectively, and TP removal could be increased by 52 to 74 percent in the BNR processwith 50 to 100 percent FWD usage, respectively [Leverenz, 2013, p. 30].

Figure 5 – Change in total Phosphorus. The influent and effluent TP in three wastewater
scenarios [Leverenz, 2013].

20

Figure 6 – Change in Nitrogen. The influent (TKN) and effluent (TN) in three wastewater
scenarios [Leverenz, 2013].


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


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



Both the COD removal and total nitrogen removal increased. The rbCOD/COD ratio
increased from 0.20 to 0.25 and the COD/TN ration increased from 9.9 to 12 with a
specific denitrification rate of about 0.06 kg NO3-N/(kg MLVSS day) [Battistoni, 2007,
p. 893].
The COD and total nitrogen removal increased, creating a denitrification efficiency of
85% and a 39% reduction of energy requirements [Battistoni, 2007, p. 893].
The composting system does not impact the waterborne wastewater system, while thefood waste disposer system is estimated to cause some minor increases in discharges ofnutrients and heavy metals to water. All impacts in both systems are rather small[Karrman, 2001].
At a 50% disposer market share, disposers are unlikely to affect biosolids reuse, themarine environment, or energy consumption [CRC, 2000].
The BOD increase in the effluent due to disposer usage equates to a 0.01 mg/L dissolved
oxygen decrease in New York Harbor in 10 years (de minimis impact) [New York City
Department of Environmental Protection, Executive Summary, 1997].
Combined sewer overflow total stream BOD concentration increased 5% and TSS 2%
over baseline from disposer usage. In the worst case area, the 4 mg/L minimum dissolved
oxygen standard was exceeded by 1.5% over the baseline. This increase is considered to
be de minimis [New York City Department of Environmental Protection, Executive
Summary, 1997].
At a 20% disposer market share, effluent quality can be maintained through operative
WWTP adjustment. A higher market share will necessitate plant expansion, but will takemany years to occur [Shpiner, 1997].

3.5 Fats, Oils, and Greases

FOG accumulation in sewer lines has become a global challenge for the management

21

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

and sustainability of sanitary sewer systems [He, 2017, p. 1212].
FOG deposits are formed through saponification between calcium and FFAs andaggregation of excess calcium or FFAs [He, 2017, p. 1212].
A small number of FOG deposits were found in pipes connected to upstream FWDs.
However, FWDs were not the major contributors to the formation of FOG deposits[Mattsson, 2014, p. 8].
Williams, 2012 research identified two possible mechanisms that may affect theformation and properties of FOG deposits in sewers [Williams, 2012, p. 6327]
o Transformation of fatty acids from unsaturated to saturated form [Williams, 2012,
p. 6327].
o Biocalcification where higher levels of water hardness lead to harder deposits
with higher melting points [Williams, 2012, p. 6327].
An introduction of FWDs will probably not lead to a significant increase in fat in thesewer system considerably [Clauson-Kaas, 2011, p. 57].
FFAs are likely to react with calcium ions by means of van der Waals forces orelectrostatic repulsion (DLVO theory) [He, 2011, p. F].
The primary lipid reacting in the FOG deposits was palmitic acid (C16H32O2). Other lipids
commonly found include oleic (C18H34O2) and linoleic acid (C18H32O2) [He, 2011, p. C].
Deposits are likely formed primarily from free fatty acids (FFAs) reacting with ions suchas calcium [He, 2011, p. F][Keener, 2007, p. 2241].
The saturated fats and calcium levels in the FOG deposits are higher than backgroundlevels, suggesting that a chemical process is responsible for deposit formation [Keener,
2007, p. 2246].

3.6 Septic Systems
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

People in rural settings should be able to have the same appliances as those living incities, including garbage disposals, but proper design of the septic system is important[Seabloom, 2004, p. 41].
The increase of the organic strength of the wastewater from garbage disposals may havean impact on the performance of the septic tank [Seabloom, 2004, p. 41].
In-sink garbage disposal devices increase scum accumulation by approximately 34
percent but increase sludge only 2 percent [Seabloom, 2004, p. 41].
It is unclear whether septic tanks must be larger to accommodate garbage disposals[Seabloom, 2004, p. 41].
COD increase in the effluent may have an impact on the performance of the septic system[Lin, 2019, p. 7].
Increases in TN and TP were minimal [Lin, 2019, p. 7].
FW substantially increased the depth and volume of the scum layer in the experimenttank [Lin, 2019, p. 7].
FW more biodegradable and accumulates more in the scum layer [Lin, 2019, p. 7].
Addition of FW on septic performance and pumping frequency will be insignificant or
negligible [Lin, 2019, p. 7].

4.0 Alternative Management Comparisons

22
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


Integrating disposers in a developing economy with a high fraction of food waste is a
viable option to reduce emissions for carbon trading; carbon emissions are reduced by
42%; cost savings of ~28%; economic savings attractive even after adding wastewaterand sludge management costs [Maalouf, 2017, p. 461].
New disposer owners typically process 30% of their food waste with disposers[InSinkErator, 2016, p. 2].
Using a disposer in combination with advanced wastewater treatment results in the lowest
primary energy demand and a lower global warming potential as compared to alternative
food waste management methods [InSinkErator - Executive Summary “Systems for theManagement and Disposal of Food Waste,” 2011, p. 2].

4.1 Landfills
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

According to the EPA, after MSW has been recovered by recycling and composting, foodwaste is the largest component of MSW discarded to the landfill in the US at 21.1%[EPA, 2013, p. 7].
FWDs would decrease the amount of moisture in the garbage by 10%. This reduction ofmoisture in the garbage results in a 16% higher calorific value for incineration from15,345 kJ/kg to 17,783 kJ/kg [Tongji University, 2013].
In a study in PuDong, the use of FWDs reduced the amount of wet waste in garbage by
10%. Based on current waste generation rates, this could equate to a reduction of over1000 tons per day in Shanghai [Tongji University, 2013].
If organic waste is removed from garbage collection, the amount of garbage is reduced byapproximately 20-30%, which also results in fewer odor problems and better hygiene forworkers who collect the garbage [Clauson-Kaas, 2011, p. 59].
Food waste is the single largest component of municipal solid waste sent to landfills andmany communities worldwide are focusing efforts to divert this organic waste in order toreduce greenhouse gas emissions at landfills [InSinkErator - Executive Summary“Systems for the Management and Disposal of Food Waste,” 2011, p. 2].
Using a disposer in conjunction with any of the eight wastewater treatment systems
results in lower global warming potential than alternative landfilling options[InSinkErator - Executive Summary “Systems for the Management and Disposal of Food
Waste,” 2011, p. 2].
Using a wastewater treatment route rather than a landfill in an area with 30,000
households would result in a carbon footprint reduction of 1.9 million kg, which is theequivalent of not driving 4.6 million miles [InSinkErator - Executive Summary “Systems
for the Management and Disposal of Food Waste,” 2011, p. 2].
A study in Surahammar, Sweden, reported that the waste diverted to landfills decreased
from 3600 tons/year in 1996 to 1400 tons/year in 2007, after the installation of FWDs
increased from 0-50% [Evans, 2010, p. 1].
Characteristics of Collected Garbage in landfills as compared to cases with no FWD use[Yang, 2009, p. 17]
o Dry ratio of food waste declined by more than half [Yang, 2009, p. 17]
o Moisture content decreased at least by half [Yang, 2009, p. 17]
o Combustible matter increased about at least 1.7 times [Yang, 2009, p. 17]
o Lower heating value increased about at least 2.0 times [Yang, 2009, p. 17]

23
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
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

Lower heating value of flammable garbage collected after FWD installation increased to12,500 kJ/kg [Yang, 2009, p. 23].
Raising the lower heating value leads to less fuel needed for the incineration process ofwaste [Yang, 2009, p. 23].
Raising the lower heating is more suitable for use as a solid fuel, rather than being solid
waste [Yang, 2009, p. 23].
Flammable garbage with a higher lower heating value (greater than 12,560 kJ/kg) andlower moisture content is best for use as a solid fuel, and the presence of food waste
disposers provides these conditions [Yang, 2009, p. 23].
According to Yang (2007), through field surveys regarding the use of FWDs in a villageof 327 people with a 97% disposer penetration, the average reduction rate of garbage
being sent to landfills was 31% [Yang, 2009, p. 24].
Using FWDs causes a decrease in the generation rate of garbage being sent to landfills, so
a cost-savings benefit in terms of garbage collection and transportation can be obtained
and materials recycling and thermal energy recovery will become easier [Yang, 2009, p.
24].
In this study, the introduction of food disposers into the waste and wastewater
management systems led to net economic benefits that ranged between 7.2% and 44.0%
of the current solid waste management cost. Food waste disposers can constitute a viableoption (economically and environmentally) that could reduce the load on the solid waste
stream and minimize the amount of end waste requiring landfilling [Marashlian, 2004].
The neuslavage study shows increased upper respiratory infections for garbage collectors
than supervisors related to microbiological exposure during work [CRC, 2000].
The Department of Sanitation recognizes the potential of disposers to make a positive
impact in New York City residential waste management. Benefits include reduced odors
and pest attraction, and better separation of recyclables [New York City Department ofEnvironmental Protection, 1997].
At a 38% disposer market share, grinding 50% of the food waste through disposers willsave $4 M in solid waste export costs [New York City Department of Environmental
Protection, Executive Summary, 1997].

4.2 Composting and Curbside Food Waste Collection

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




FWD can be used in conjunction with curbside food waste collection (CFWC) tomaximize the overall diversion. Therefore, FWD and CFWC are complementary, rather
than competing technologies [Leverenz, 2013, p. 4].
FWD eliminates the need for additional processing at the wastewater treatment plant,
unlike CFWC. CFWC requires additional processing besides grinding to eliminate theadditional debris and contaminants in the food waste [Leverenz, 2013, p. 10].
Total cost for composting facility is estimated at $40 per ton [WERF, 2012, p. A23].
Based on several steps for the compost alternative, such as transportation to compost
facility, ventilation, handling, turning, composition, land application, application as
fertilizer the total CO2 emissions for composting is 1050 tons/year [WERF, 2012, p.
A25].
The GWP for composting is -14 kgCO2e/tKFW whereas the GWP for using a FWD in
conjunction with AD is -168 kgCO2e/tKFW [Evans, 2007, p. 4].

24
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


FWDs are not meant to discourage composting. Rather, FWDs can be seen as aconvenient and hygienic method to divert food waste from landfills [Evans, 2007, p. 5].
The main difference between using a FWD with AD and composting is that using a FWD
creates energy (renewable fuel from the CH4), whereas the composting method consumes
energy [Evans, 2007, p. 42].
Food waste collection followed by anaerobic digestion and biogas utilization in power
plants has been judged more positive than separate collection followed by composting [deKoning, 2004].
The food waste disposer is designed to grind only food waste. Materials other than foodwaste (ex., bottle caps, textiles, etc.) will lead to device jamming. Thus, the disposer is anatural selector of food waste. In contrast, composting largely depends upon the
education and goodwill of participants as to the quality of collection [CECED, 2003].
The food waste disposer system appears to be slightly less costly than central composting
when only the costs for water and refuge handling are considered, and the user pays forthe purchase and installation of the disposer themselves [Karrman, 2001].
The food waste disposer alternative causes 3 times less global warming than thecomposting alternative, due to the reduction of truck transport [Karrman, 2001].
Concentrations of bacteria and molds that can interfere with human health and wellbeing
are greater when there are organic waste buckets and bins used for composting purposes[CRC, 2000].
Most people are unwilling to separate food scrap for Department of Sanitation pickup[New York City Department of Environmental Protection, 1997].
Home composting produces a high strength (BOD) leachate when food waste is present.
There is no readily available mechanism to manage this leachate [Waste Management
Research Unit, 1994].
Methane has a much greater greenhouse effect (on the environment) than the equivalentof carbon dioxide. Environmentally, therefore, it is desirable to minimize methane
release. There is no readily available mechanism for achieving this with householdcomposting. In contrast, landfills and sewage treatment works can be constructed tomaximize methane recovery as a fuel [Waste Management Research Unit, 1994].

5.0 Life Cycle Analyses
5.1 “Sustainable Food Waste Evaluation”
Water Environment Research Foundation (WERF)
The Life Cycle Analysis is a comparison of five systems for the processing wastes based on arepresentative community of 100,000 people in North America. The five systems are:
1.
2.
3.
4.
5.

Mixed Material Recovery Facility (MRF)
Landfill
Wastewater Treatment Plant (WWTPP)/HauledComposting
Wastewater Treatment Plant (WWTP)/Sewered

25
The LCA analyzed capital and operating costs, carbon footprint, space footprint, labordemands, diesel fuel demand, electricity demand, and water demand for each of the fivesystems.
Capital and Operating Costs: The costs of the five systems ranked from highest to lowest
cost are: Mixed material recovery facility, landfill, WWTP/hauled, composting, andWWTP/sewered.
Carbon Footprint: The carbon footprint (CO2e) from the five food waste management
options ranked from highest to lowest is: landfill, mixed MRF, WWTP/sewers, compost,
WWTP/hauled. The lower carbon footprint in the WWTP/hauled method is probably due tothe electricity generation from biogas produced by the digesters. The WWTP/sewered
alternative has a relatively high carbon footprint, probably due to the uncertainty of themethane released in the sewers. Additionally, since there is little information known about
the anaerobic decomposition that occurs in the sewers, so the CO2e emissions for the
WWTP/sewered alternative provides a large degree of uncertainty.
Space Footprint: The space footprint, or area requirements, of the alternative methods
ranked from highest to lowest are: composting, landfill, mixed MRF, WWTP/hauled,
WWTP/sewers.
Diesel Fuel Demand: The diesel usage for the five systems ranked from highest usage tolowest is: composting, mixed MRF, landfill, WWTP/hauled, WWTP/sewered.
Water Demand: The water demand for the five systems ranked from highest water demand
to lowest water demand (measured in Mgal/year) is: WWTP/sewers, WWTP/hauled, mixed
MRF, composting, landfill.
Overall, the use of a FWD has the lowest cost of all other alternatives studied, a small space
footprint, and low diesel requirements. However, the use of a FWD does require water. Thereis a greater electricity use to account for the aeration necessary to process the addition of thefood waste, but there is also additional energy production due to anaerobic digestion.
[WERF, 2012]

5.2 “Life Cycle Assessment of Systems for the Management and Disposal of Food
Waste”

26
PE Americas
The Life Cycle Analysis (LCA) is a comparison of a total of twelve end-of-life disposal
options, including two landfilling options, eight wastewater treatment options that occur inconjunction with a FWD, one incineration system, and one composting system. The twelve
systems are:
1. Landfill with Generation
2. Landfill with Flare
3. Extended Aeration
4. Extended Aeration/Landfill
5. Extended Lime/Slab6. Conventional Treatment/Incineration
7. Conventional Lime Slab
8. Conventional Treatment/Anaerobic Digestion/Flare
9. Conventional Treatment/Anaerobic Digestion/Boiler
10. Conventional Treatment/Anaerobic Digestion/Cogeneration
11. Incineration
12. CompostingThis LCA found that using a disposer in conjunction with any of the eight wastewater
treatment systems results in lower global warming potential than both landfilling options.
Additionally, using a disposer in combination with advanced wastewater treatment results inthe lowest primary energy demand as compared to the landfill systems as well as the wasteto-energy and emissions-controlled composting systems.
[PE Americas, 2011]
5.3 “Life-Cycle Comparison of Five Engineered Systems for Managing Food Waste”
Dr. Carol Diggelman, University of Wisconsin
The Life Cycle Analysis (LCA) is a comparison of five systems for the processing of 100 kg
of food waste. The five systems are:
1.
2.
3.
4.
5.

Food Waste Disposer/Wastewater Treatment Plant (FWD/WWTP)
Municipal Solid Waste Collection/Landfill (MSW/L)
Municipal Solid Waste Collection/Compost (MSW/C)
Municipal Solid Waste Collection/Incineration (MSW/I)
Food Waste Disposer/On-Site Septic System (FWD/OSS)The LCA analyzed land requirements, total system energy, total system materials, total
emission to the environment, and total system cost for each method. The ranking forthese areas were:Total land requirements: FWD/WWTP < MSW/I < MSW/L < MSW/C < FWD/OSS

27
Total system energy requirements: FWD/WWTP < MSW/L < MSW/C < MSW/I <FWD/OSS
Total system materials: MSW/C < MSW/I < FWD/WWTP < MSW/L < FWD/OSS
Total flows to environment: MSW/C < MSW/L < MSW/L < FWD/WWTP < FWD/OSS
Total system costs: MSW/L < MSW/C < FWD/WWTP < MSW/I < FWD/OSS
Overall, of the five systems, the FWD/WWTP has the lowest municipality cost (systemcost due to disposer cost, which is paid by the homeowner); least air emissions; converts
food waste to a recycled resource; is the most convenient system of food waste disposal;
is the most likely system for organic source separation; and overall is the mostenvironmentally friendly and sustainable option.
[Diggelman, 1998]
5.4 “Assessment of Food Disposal Options in Multi-Unit Dwellings in Sydney”
CRC for Waste Management and Pollution Control Limited
The Life Cycle Analysis (LCA) is a comparison of four systems for the processing of 182
wet kg of food waste. The four systems are:
1.
2.
3.
4.

Food Waste Disposer/Wastewater Treatment Plant (FWD/WWTP)
Home Composting (HC)Co-Disposal or Municipal Solid Waste Collection/Landfill (MSW/L)
Centralized Composting or Municipal Solid Waste Collection/Compost (MSW/C)

The research was undertaken as five separate but interlinked studies examining technicaland operational, environmental, economic, social acceptance, and microbial risk impacts.
[Note: The beneficial use of by-products (i.e., compost and biosolids) was not part of thestudy. Also, the amount of recovered energy is uncertain should biogas be used forenergy recovery. Electricity generation from biogas can lead to high environmental
improvements for the FWD/WWTP and Co-Disposal (MSW/Landfill) systems. However,
little biogas was being recovered at the WWTP (Bondi STP) that was used in the study.
In addition, the Bondi STP is a “high rate primary” plant, thus, nutrients (nitrogen andphosphorus) are released to treated effluent, which caused a poor eutrophication rating
for the FWD/WWTP system.]
Environmental Impacts: Home Composting has the smallest environmental impacts.
The FWD/WWTP system ranked second in terms of energy consumption, global
warming potential, and eutrophication potential; but fourth in terms of human, aquaticand terrestrial toxicity potential. Co-Disposal ranked second highest in toxicity potentialand eutrophication potential; ranked slightly behind FWD/WWTP for energy
consumption and acidification; and had the lowest ranking for global warming potential.
Centralized Composting has a relatively poor environmental performance due to its
energy intense collection activities, ranking fourth for energy and acidification; and third
in the remaining categories.

28

System Cost Comparison: Home Composting is the least expensive option for multiunit residents; then Centralized Composting; Co-disposal; and FWD/WWTP is the mostexpensive (due to a high initial unit and installation cost paid by homeowner). From asystem point-of-view, the FWD/WWTP system was again the most expensive; CoDisposal (the current system utilized by Sydney) has landfill space and does not require
capital investment; Centralized Composting would necessitate capital investment. The
FWD/WWTP system may require capital investment beyond a 25% market share.
Health Risk Comparison: The FWD/WWTP system may only marginally increase therate of sanitary sewer overflows during periods when the sewer is flowing at 100%.
Home Composting without pet fecal waste or meat products addition should result in
acceptably low infection rates for all pathogen groups. Centralized Composting(including human fecal waste) should be satisfactory from the point of no significant
pathogen risks. Overall vector-based diseases were not considered significantly different
due to the operation of food waste disposal units and domestic composting containers.
Social Impact Comparison: Disposal of food with municipal waste was judged as theleast satisfactory option (current Sydney system). Home Composting was judged
impractical for multi-unit dwellings. FWD/WWTP and food waste collection with
Centralized Composting were much more appropriate, provisional on the level oftreatment that would enable reuse of the waste residuals (which was not studied).
[CRC for Waste Management and Pollution Control Limited, 2000]

29

6.0 Research References
ASSE International. June, 2006. “Performance Requirements for Plumbing Aspects ofResidential Food Waste Disposer Units – ASSE Standard #1008.”
Association of Home Appliance Manufacturers (AHAM). 2009. “Food Waste Disposers.”
Battistoni, Paolo, Francesco Fatone, Daniele Passacantando, and David Bolzonella. Water
Research, 2007. “Application of Food Waste Disposers and Alternate Cycles Process in SmallDecentralized Towns: A Case Study.”
Bolzonella, David, Paolo Pavan, Paolo Battistoni, and Franco Cecchi. Department of Scienceand Technology. University of Verona. 2003. “The Under Sink Garbage Grinder: A Friendly
Technology for the Environment.”
CECED – European Committee of Manufacturers of Domestic Appliances. Spring 2003. “Food
Waste Disposers – An Integral Part of the EU’s Future Waste Management Strategy.”
Chowdhury, M.M.I., M. Kim, B.M. Haroun, G. Nakhla, and M. Keleman. 2016. Water
Environment Research. “Flocculent Settling of Food Waste.”
Clauson-Kaas, Jes and Janus Kirkeby. DANVA, August, 2011. “Food Waste Disposers: Energy,
Environmental and Operational Consequences of Household Residential use.”
CRC for Waste Management and Pollution Control Limited. December, 2000. “Assessment ofFood Disposal Options in Multi-Unit Dwellings in Sydney.”de Koning, Dr.ir. J. Delft University of Technology. July 2004. “Environmental Aspects of Food
Waste Disposers.”
de Koning, Dr.ir. J. and Prof.ir. J.H.J.M. van der Graaf. Delft University of Technology. April
1996. “Kitchen Waste Disposer Effects on Sewer System and Wastewater Treatment.”
Diggelman, Dr. Carol and Dr. Robert K. Ham. Department of Civil and Environmental
Engineering – University of Wisconsin. January 1998. “Life-Cycle Comparison of Five
Engineered Systems for Managing Food Waste.”
DeOreo, William. Aquacraft, Inc. Water Engineering and Management, July 2011. “California
Single-Family Water Use Efficiency Study.”
EPA – US Environmental Protection Agency. June, 2013. “Advancing Sustainable Materials
Management: 2013 Fact Sheet.
Evans, Tim. June, 2007. “Environmental Impact Study of Food Waste Disposers."

30
Evans, Tim, Per Andersson, Asa Wievegg, and Inge Carlsson. Water and Environment Journal,
2010. “Surahammar: A Case Study of the Impacts of Installing Food Waste Disposers in 50% ofHouseholds.”
He, Xia, et al. Environmental Science and Technology. April, 2011. “Evidence for Fat, Oil, andGrease (FOG) Deposit Formation Mechanisms in Sewer Lines.”
He, Xia, L. Reyes III, J. Ducoste. 2017. Critical Reviews in Environmental Science andTechnology. “A critical review of fat, oil, and grease (FOG) in sewer collection systems:
Challenges and control.”
Hernandez, Gerald L., Kenneth R. Redd, Wendy A. Wert, An Min Liu, and Tim Haug. BioCycle
Magazine. January 2002. “Los Angeles Digesters Produce Energy From Airport Food
Residuals.”
Hernanadez, Gerald L., Kenneth R. Redd, Wendy A. Wert, An Min Liu, and Tim Haug. 2002.
“Hyperion Advanced Digestion Pilot Program.”
Imanishi, Akio. National Institute for Land and Infrastructure Management, March 2005.
“Report on Social Experiment of Garbage Grinder Introduction.”
InSinkErator. July 2011. “Executive Summary – Systems for the Management and Disposal of
Food Waste.”
InSinkErator. 2016. “The Food Waste Disposer as a Municipal Tool for Waste Diversion.”
Jones, P.H. 1990. “Kitchen Garbage Grinders - The Effect on Sewerage Systems and Refuse
Handling.”
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.”Karrman, Erik, Mattias Olofsson, Bernt Persson, Agneta Sander, and Helena Aberg. Recycling
Board of Goteborg, Sweden. 2001. “Food Waste Disposers – A Solution for Sustainable
Resource Management? A Pre-Study in Goteborg, Sweden.”
Keener, Kevin M, Joel Ducoste, and Leon M. Holt. December, 2007. “Properties Influencing
Fat, Oil, and Grease Deposit Formation.”
Kegebein, Jorg, Erhard Hoffmann, and Prof. Hermann H. Hahn. Institute for Municipal Water
Treatment, University of Karlsruhe, 2001. “Co-Transport and Co-Reuse – An Alternative to
Separate Bio-Waste Collection?”
Keleman, Michael. 2013. “Let’s Clear the FOG.”
Kim M. G. Nakhla, M. Keleman. Journal of Environmental Management. February 2019.
“Modeling the Impacts of Food Wastes on Wastewater Treatment Plants."

31
Kim, M, M.M.I. Chowdhury, G. Nakhla, and M. Keleman. Bioresource Technology, February,
2015. “Characterization of Typical Household Food Wastes from Disposers: Fractionation ofConstituents and Implications for Resource Recovery at Wastewater Treatment.”
Leverenz, Harold and George Tchobanoglous. May 2013. “Energy Balance and Nutrient
Removal Impacts of Food Waste Disposers on Wastewater Treatment.”
LGA (Local Government association). October 2012. “The Potential of Food Waste Disposal
Units to Reduce Costs.”
Lin, Hongjian, Y. Wang, L. van Lierop, C. Zamalloa, C. Furlong, M. Keleman, and B. Hu. 2019.
Waste Management & Research. “Study of Food Waste Degradation in a Simulated Septic
Tank.”
Maalouf, Armani, M. El-Fadel. 2017. Waste Management. “Effect of a Food Waste Disposer
Policy on Solid Waste and Wastewater Management with Economic Implications ofEnvironmental Externalities.”
Marashlian, Natasha and Mutasem El-Fadel. American University of Beirut, Lebanon. October
2004. “The Effect of Food Waste Disposers on Municipal Waste and Wastewater Management.”
Mattsson, Jonathan, Annelie Hedstrom, and Maria Viklander. May 2014. Environmental
Technology. “Long-Term Impacts on Sewers Following Food Waste Disposer Installation in
Housing Areas.”
Metcalf and Eddy. 2014. “Wastewater Engineering. Treatment and Resource Recovery.”
Morris, Jeffrey, Scott Matthews, and Clarissa Morawski. Waste Management, 2012. “Review
and Meta-Analysis of 82 Studies on End-of-Life Management Methods for Source Separated
Organics.”
Nakhla, Dr. George. Department of Chemical and Biochemical Engineering, Western University,
London, Ontario, Canada, September 2014. “Settleability and Detailed Organics
Characterization of Food Wastes.”
New York City Department of Environmental Protection. 1997. “Executive Summary - The
Impact of Food Waste Disposers in Combined Sewer Areas of New York City.”
New York City Department of Environmental Protection. June 1997. “The Impact of Food
Waste Disposers in Combined Sewer Areas of New York City.”
Nichols, Andy, Simon Tait, and Abbi Legge. December 2019. University of Sheffield. “Food
Waste Disposer Particle Characterisation.”
PE Americas. February 2011. “Life Cycle Assessment of Systems for the Management andDisposal of Food Waste.”32
Rosenwinkel, K.H. and D. Wendler. Institute for Water Quality and Waste Management,
University of Hanover (ISAH), 2001. “Influences of Food Waste Disposers on Sewerage
System, Wastewater Treatment and Sludge Digestion.”

Seabloom, Robert W., T. Bounds, T. Loudon. 2004. “University Curriculum Development for
Decentralized Wastewater Management.”
Shpiner, Ram. Submitted to the Senate of the Technion – Israel Institute of Technology. January
1997. “The Effect of Domestic Garbage Grinding on Sewage Systems and Wastewater
Treatment Plants.”
Strutz, Bill. Internal Information, October, 2005. “Electricity Use of Food Waste Disposers.”
Tendaj, M, et al. 2008. “Kitchen Disposal Units (KDU) in Stockholm, Stockholm Water’s PreStudy on the Preconditions, Options, and Consequences of Introducing KDUs in households inStockholm.”
Terpstra, Prof. drs. P.M.J. Agricultural University Wageningen. April 1995. “Kitchen Waste
Disposal Treatment: An Evaluation.”
Thomas, Philip. Water and Environment Journal, 2010. “The Effects of Food Waste Disposers
on the Wastewater System: A Practical Study.”
Tongji University. 2010. “Environmental and Economic Cost Benefit Analysis of Food Waste
Disposers.”
Tongji University. 2013. “Report for Food Waste Disposer Pilot Program in PuDong andEnvironmental Impact Assessment.”
Waste Management Research Unit – Griffith University. August 1994. Executive Summary.
“Economic and Environmental Impacts of Disposal of Kitchen Organic Wastes Using
Traditional Landfill – Food Waste Disposer – Home Composting.”
WERF – Water Environment Research Foundation. Executive Summary – Cost Affective,
Sustainable Alternatives to Landfills for Managing Food Waste.
WERF – Water Environment Research Foundation. 2012. Sustainable Food Waste Evaluation –Final Report.
WERF – Water Environment Research Foundation. 2015. “A Guide to Net-Zero Energy
Solutions for Water Resource Recovery Facilities.”
Williams, J.B, C. Clarkson, C. Mant, A. Drinkwater, and E. May. Water Research, 2012. “Fat,Oil, and Grease Deposits in Sewers: Characterization of Deposits and Formation Mechanisms.”

33
Yang, Xinmi, Takao Okashiro, Katsuhiko Kuniyasu. Japan Education Center of Environmental
Sanitation, August 2009. “Impact of Food Waste Disposers on the Generation Rate andCharacteristics of Municipal Solid Waste.”
Yoshida, Ayako, et al. National Institute for Land and Infrastructure Management, Ministry ofLand, Infrastructure and Transport, Japan. “Impacts of Food Waste Disposers on Sewage
Systems.”