Title: Re: [GreenYes] Re: Growing Global Interest in Food Waste
Here are some other discussions:|
- Marashlian, N. and M. El-Fadel (2005). "The effect of food waste
disposers on municipal waste and wastewater management." Waste
Management and Research 23(1): 20-31.
- Konheim, C. S. and W. B. Pressman (1998). Effects of residential
food waste disposers on municipal wastewater and solid waste
management. 91st Annual Meeting and Exhibition of the Air and Waste
Management Association, June 14-18, San Diego, CA, Air and Waste
Disposal of putrescible solid wastes remains a challenge
for municipalities and local authorities. Decomposing wastes breed
odors, attract vermin, are costly to collect, transport and process,
and, if disposed of in landfills, generate leachate, organic compounds,
some toxic, and large quantities of global warming gases. Most
municipalities have sought to reduce this burden by encouraging use of
kitchen food waste disposers (FWD), integrating treatment of food and
sewage solids. In most of the United States, the proportion of food
waste in the municipal solid waste (MSW) stream has decreased over the
period 1960 to 1994 from 13.9% to 6.7% of the MSW collected(1). This is
attributed more to the growing use of food waste disposers than to the
increase in non-organic waste(2). However some municipalities are
accompanying use of FWDs with separate collection of food wastes or
mixed waste processing to produce a biosolid for land application.
Moving in a different direction, recently, two wastewater treatment
agencies have adopted policies restricting use of FWDs by commercial
FWDS are used to dispose of food wastes in about 45% of U.S.
On average, the in-sink appliances grind about half of the 0.30
lbs/capita/day of wet food waste generated in a typical household,
leaving 0.15 lbs/cap/day of food waste, 70% of which is water(4), to be
added from the FWDs via the collection system to wastewater treatment
plants (WWTPs) where they add 0.05 lbs/capita/day of food solids to
sewage solids. The remaining 0.15 lbs/cap/day of wet food waste are
added to MSW.
- Ketzenberger, B. A. (1995). Part 1 - Water Use by Kitchen Food
Waste Disposers in Households. Part 2 - Effect of Ground Food Wastes
on Septic Tank/Soil Absorption Fields - Critical Review of Literature.
Civil and Environmental Engineering. Madison, University of Wisconsin:
134. Master Thesis.
- Evans, T. (2007). Environmental Impact Study of Food Waste
Disposers, Tim Evans Environment: 53.
This study examines the financial and environmental impacts of food
waste disposers (FWD) and finds that they provide a cost-effective,
convenient and hygienic means of separating putrescible domestic
kitchen food waste (KFW) at source and diverting it from landfill. The
study also finds that this route costs less and has a smaller global
warming potential than the routes comprising kerbside collection
followed by centralised composting or landfill.
Home composting is ideal for garden waste because of both treating and
also using the treated material where it is generated (the proximity
principle). Bokashi treatment and wormeries have enthusiastic
followings but users still need to have somewhere to use the treated
material. Some householders are unable (e.g. apartment dwellers) or are
not inclined to practise home composting.
In terms of Best Value Performance Indicators, FWD reduce BV84
(kilograms of household waste collected per head of population), BV86
(cost of household waste collection per household) and BV87 (cost of
waste disposal per tonne municipal waste).
The National Audit Office concluded that England will not achieve the
Landfill Directive targets without a step change in plans and that
emphasising recycling alone is unlikely to be the answer. Part of the
problem is lack of infrastructure for treating biodegradable municipal
waste and this is linked with the delays consequent on the planning
process. H&W (Herefordshire Council and Worcestershire County
Council) have been pioneering in promoting installation of FWD. FWD
have the benefit of separating at source a difficult fraction of
biodegradable MSW (because it is wet and malodorous) and diverting it
using existing infrastructure and without entailing any regulatory
The net global warming potential1 (GWP) of separate collection and
treatment of KFW by composting is -14 kgCO2e/tKFW allowing for
fertiliser offset and carbon sequestration when the compost is used on
land. For households with FWD feeding to wastewater treatment works
where sludge is treated by anaerobic digestion, the biogas is used as
renewable energy and the biosolids are used on land (which is the
pathway for Severn Trent Waterﾒs works in H&W and Welsh Waterﾒs
works in Herefordshire) the GWP is better than -168 kgCO2e/tKFW2. In
contrast, landfill is +743 kgCO2e/tKFW.
Assuming that KFW is 17.6% of household waste, the cost of collecting
and disposing KFW via the solid waste route in H&W averages £18.63
per household*year and the quantity is 180 kgKFW per household*year
(2005/06 actuals). This is the approximate annual saving for each
installed FWD. The saving will increase, and the payback period will
decrease, as the cost of treating KFW increases with ABPR compliant
treatment replacing landfilling. For example, letsrecycle.com estimates
the current gate fee for composting KFW at a site that complies with
the Animal By-Products Regulations is £42-52 /t. By February 2007, 640
FWD had been installed under the H&W cashback scheme at a total
cost of £39,650, i.e. £62 per FWD, which is a payback period [at direct
cost current savings] of only 3 years and 4 months. The ground KFW is
transferred to the wastewater collection and treatment system and
therefore adds somewhat to the costs of the water company.
The value to H&W could be even greater when LATS (Landfill
Allowance Trading Scheme) is factored into the equation. The LATS
penalty is currently £150 per tonne of biodegradable municipal waste
landfilled in excess of that permitted by allowances held. There could
be additional penalties in the target years 2010, 2013 and 2020. The
Local Government Association has warned that prices for allowances
could be high from 2008/09 onwards, with a "serious deficit" of
allowances potentially arising after 2009/10.
Water companies are understandably concerned about changes that might
adversely affect demands on water resources or that would increase
sewer blockages; field trials in several countries (none has yet been
undertaken in the UK) have shown that FWD do not affect water usage or
accumulation in sewers significantly. Wastewater treatment works (WwTW)
are designed to treat biodegradable material suspended in water, i.e.
similar to the output of FWD. Ground KFW has been found actually to
improve the composition of wastewater for the advanced nutrient removal
processes that are now being demanded of WwTW (this is because it has
more carbon in relation to nitrogen or phosphorus than normal sewage).
The additional cost for water companies depends on the route for
treating and using or disposing the sewage sludge; for the route most
usual in H&W it would be about £0.68 per household*year, this is
only 4% of the cost of the MSW-landfill route. However, the cost could
be as much as £8.38 for a WwTW that incinerates its sludge and does not
generate electricity (not the case in the H&W area).
Overall, food waste disposers appear to be a very cost effective means
of separating putrescible kitchen waste at source and diverting it from
landfill. The carbon footprint of FWD feeding to a WwTW with anaerobic
digestion (AD) and electricity generation (CHP)3 is competitive with
separate collection of KFW delivering to centralised AD with CHP and
significantly better than centralised composting. They are convenient
and hygienic for householders but do not discourage home composting.
They avoid the problems of odour and vermin that can be associated with
separate collection via the solid waste route.
Kendall Christiansen wrote:
comment/request, at http://www.insinkerator.com/environmental.shtml
you will find six contemporary studies – beginning with the UWisconsin
(’98) which Carol Diggelman conducted (later published in “Waste
Management and Research”) and ending with last year’s report (exec
summary) on the “Sink Your Waste” initiative in
Herefordshire/Worcestershire County cited in the WSJ article – along
some commentaries. The study from Sydney
also independently assessed four options for food scrap management.
Additional studies and commentaries are available from me, upon
request, as is
a comprehensive document summarizing findings – by topic, to make it
to find particular answers – from seventeen (17) studies, for those who
really want to dive into this topic.
worth noting that in the U.S. food waste
disposers daily divert millions of tons of food scraps from solid waste
transport and disposal systems. Probably fair to say that even in the
Area that disposers daily divert a significant amount of residential
scraps – and have done so for decades. After all, not much
difference between food and human waste – both @ 70% water, with
chemical composition. Plenty of studies of impacts/benefits re
treatment systems, but there’s also substantial evidence in the form of
the ‘wisdom of crowds’ of nearly all municipalities in the U.S.
chosen to allow disposers for decades. Dave Biddle’s Philadelphia is
example, where commercial disposers have been encouraged for @ 15
part to reduce odors and vermin caused by food waste stored in
point of the WSJ article is that where
disposers are not common for historical reasons, and pressure is
find effective answers, that municipalities are now making informed
about how best to manage food scraps, with some choosing to trade
in/reliance upon wastewater treatment plants and biosolids processing
collection and the challenge/cost of siting/operating composting
The article didn’t mention it, but that’s essentially the analysis
that led NYC in 1997 – after a decade of study – to fully permit
residential disposers (previously legal only in newer areas), and is
now in the
midst of studying the efficacy of commercial disposers for the same
albeit with a new imperative: of reducing GHG emissions from whatever
system is pursued, vs. continuing to ship 5,000 TPD of residential and
food waste to distant landfills.
As to Dan’s
concern about sewer
overflows, that issue exists with or without disposers; the added flow
disposers is less than 1% per daily household water
In mass balance terms, using NYC as an example, its WWTPs daily handle
billion gpd; if ALL 3 million homes had and used a disposer, the added
would be perhaps 5 million gpd, or a de minimis impact – in the words
February 28, 2008
To: David Biddle
Cc: Dan Knapp; Kendall
Growing Global Interest in Food Waste Disposers
Note that the WSJ article, which I read, was not a glib endorsement but
just a descriptive report of what's happening in Malmo, Sweden
- and a few other European cities. The garbage disposall was invented
in the US
marketed here wth the post-WW2 housing boom - 50% mkt penetration now.
never had much mkt in Europe but now is being positioned as a green
there as limits of successful backyard composting are being reached in
like Germany that have done it for a while. The article reports on a
Carol Diggelman in '98 looking at 5 different ways of managing food
concluded that disposals that fed to water treatment plants w/
recovery had a more benign enviro. footprint than trucking food waste
to LFs or
even to compost fcilities. anyone have a copy of tha study? Would love
the discussion in that.
David Biddle wrote:
Kendall-I would love a copy
of the WSJ
Dan- It seems to me that the problems that biosolid systems are having
country are more a function of a dilapidated or under-sized
that this issue calls forth the need to seriously examine that
Also, in your climate backyard composting is probably a bit more doable
northern climates like Philadelphia, Boston, Chicago,
etc. In addition, in many cities people don’t have space, literally.
in Philly the majority of backyards are postage size. Finally, in
seen, while the residential food waste component is high, the
institutional fraction is much higher. Short of daily collection of
carts, what is a Hilton Hotel supposed to do with their 2,000+ pounds
scrap and sauces?
I’m advocating (and Kendall and I have talked about this often) for a
very careful and thorough analysis of all the options for really
problem, especially for the commercial sectors. If it means that cities
look at renovating with $200 million bond options or privatizing their
or whatever, then so be it. Certainly, if the Bay Area is struggling
you say it is, this process must already be underway. I would hope all
Waste-Heads their are looking to be a part of the solution.
David Biddle, Executive
Commercial Recycling Council
Philadelphia, PA 19118
on 2/28/08 4:16 PM, Dan Knapp at firstname.lastname@example.org
that sewage treatment plants in the San Francisco Bay Area would not be
enthusiastic about the WSJ's glib endorsement of garbage disposals to
solid waste. I have read several articles in the local press about how
these plants are so maxed out that they are sometimes forced to dump
sewage into streams that drain to the Bay. In late January one major
sewage release in Marin County amounting to millions of gallons was one
lead stories on the evening news for a couple of weeks. Following that
spill, lots of dead shorebirds were found in the area, although no
link was established. Also, sewage treatment facilitiy operators are
advising customers via mailings never
to put grease into the sewage system at all, since it creates pipe
not to mention lots of Biological Oxygen Demand.
The best option is to compost food in your own backyard along with all
trimmings, food paper, and other organics such as cotton clothing.
done it for decades, and it's very satisfying, especially when combined
growing food in the enriched soil you get when you actually use the
compost. My soil horizon in the food garden is now about eight inches
deep after fifteen years of soil amending with dozens of cubic yards of
I'm also taking carbon that used to be in the air and putting it into
where it nourishes the soil critters and fungi that help plants grow.
soil is much easier to work than the heavy clay that I had to start
clods at all, and it holds water like a sponge.
Next best is to use curbside food and yard debris collection; these
processing systems are proliferating all over the Bay Area right now.
Urban Ore, Inc., a reuse and recycling business in Berkeley, CA
for 27 years.
On Feb 28, 2008, at 11:54 AM, Kendall Christiansen wrote:
the Wall Street Journal featured a report about the growing
interest – with a focus on the EU – in the efficacy of food waste
disposers (aka garbage disposals) as an environmental management tool,
immediate diversion of food scraps from the solid waste stream, and
wastewater treatment plants to process the solids in fertilizer
energy recovery where possible. In particular, it noted the experience
several cities that have intentionally opted for disposer-based systems
food scrap management.
Given that the WSJ remains subscription-based, if you’d like a copy of
the article – as well as its Environmental Capital blog post on the
topic – please let me know and I’ll forward. If you would
like access to one or more of the reports referenced in the article,
know that, too.
151 Maple Street
Brooklyn, NY 11225
writer is senior consultant on
environmental affairs for InSinkErator, the leading manufacturer of
and commercial food waste disposers, and former Chair of NYC’s Citywide
Recycling Advisory Board
Stephan Pollard, Ph.D.-Environmental Dynamics
Cell: (479) 799-9190