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[GreenYes] Re: Growing Global Interest in Food Waste Disposers

When we consider kitchen garbage grinders and the sewage system, we need to plan with expected water shortages in mind.  Here's an update from the Environmental News Service.  

Mary Lou Van Deventer 
Urban Ore, Berkeley, CA 
To End the Age of Waste 

Big City Water Agencies Form New National Climate Alliance
SAN FRANCISCO, California, February 28, 2008 (ENS) - Realizing that "climate change poses a major long-term challenge to delivering high quality drinking water," eight of the nation's largest water agencies today announced the formation of an unprecedented coalition, the Water Utility Climate Alliance.

The alliance, which supplies drinking water to more than 36 million people, will work to improve research into the impacts of climate change on water utilities. Members will develop strategies for adapting to climate change and implement tactics to reduce their greenhouse gas emissions.

From east to west, WUCA Members are - the New York City Department of Environmental Protection, Denver Water, the Southern Nevada Water Authority and on the West Coast the Portland Water Bureau, Seattle Public Utilities, the San Diego County Water Authority, the San Francisco Public Utilities Commission, and the Metropolitan Water District of Southern California.

"Water utilities are among the first responders to the effects of climate change," said Susan Leal, general manager of the San Francisco Public Utilities Commission, which chairs the WUCA.

"Our systems are facing risk due to diminishing snowpack, bigger storms, more frequent drought and rising sea levels. We need to be organized to respond to these risks - that's why we've formed this alliance."

Patricia Mulroy, general manager of the Southern Nevada Water Authority, said, "Water agencies throughout the nation will invest hundreds of billions of dollars in infrastructure over the next 15 years alone, and those investments must be informed by climate projections that are as accurate as possible."

Emily Lloyd, commissioner of the New York City Department of Environmental Protection, said, "We need the best possible research to enhance our understanding of how climate change will impact water supplies, precipitation patterns, hydrology and water quality."

In its first official act, the WUCA provided comment today on the "Summary of Revised Research Plan" prepared by the U.S. Climate Change Science Program, a slate of 13 federal agencies with climate change research responsibilities.

The WUCA identified several key research needs that would improve the ability of the drinking water industry to develop strategies to cope with potential impacts of climate change.

The WUCA is urging the Climate Change Science Program, and all other researchers and scientists in the climate-change field, to reduce the uncertainty in climate change projections by improving and refining global climate models and applying them at the regional or local level.

The utilities say scientists should enhance the collection, maintenance and accessibility of information, making the data more useful for decision-making purposes and ensure that water providers worldwide have access to consistent climate data.

They need tools for planning, decision-making and policy-making that can accommodate deep uncertainty and the potential for abrupt climate changes, the utilities say.

And finally, the WUCA members would like to see coordination of international research efforts, particularly with those countries that are already experiencing the effects of climate change, such as Australia.

The CCSP's "Summary of Revised Research Plan" is available online at

Copyright Environment News Service (ENS) 2008. All rights reserved.

On Feb 28, 2008, at 9:05 PM, Stephan Pollard wrote:

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 Management Association.
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 food establishments.

FWDS are used to dispose of food wastes in about 45% of U.S. households(3).

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.
Executive Summary

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 bureaucracy. 

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 Waterï¾?s works in H&W and Welsh Waterï¾?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, 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:
Per Anneâ??s comment/request, at you will find six contemporary studies â?? beginning with the UWisconsin study (â??98) which Carol Diggelman conducted (later published in â??Waste Management and Researchâ??) and ending with last yearâ??s report (exec summary) on the â??Sink Your Wasteâ?? initiative in Herefordshire/Worcestershire County cited in the WSJ article â?? along with 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 â?? by topic, to make it easy to find particular answers â?? from seventeen (17) studies, for those who really want to dive into this topic.
Might be worth noting that in the U.S. food waste disposers daily divert millions of tons of food scraps from solid waste collection, transport and disposal systems.  Probably fair to say that even in the Bay Area that disposers daily divert a significant amount of residential food scraps â?? and have done so for decades.  After all, not much difference between food and human waste â?? both @ 70% water, with similar chemical composition.   Plenty of studies of impacts/benefits re wastewater treatment systems, but thereâ??s also substantial evidence in the form of the â??wisdom of crowdsâ?? of nearly all municipalities in theU.S. having chosen to allow disposers for decades.  Dave Biddleâ??s Philadelphia is one such example, where commercial disposers have been encouraged for @ 15 years, in part to reduce odors and vermin caused by food waste stored in dumpsters.
But the point of the WSJ article is that where disposers are not common for historical reasons, and pressure is growing to find effective answers, that municipalities are now making informed judgments/decisions about how best to manage food scraps, with some choosing to trade investment in/reliance upon wastewater treatment plants and biosolids processing for truck-based collection and the challenge/cost of siting/operating composting facilities.  The article didnâ??t mention it, but thatâ??s essentially the analysis that led NYC in 1997 â?? after a decade of study â?? 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 purpose, albeit with a new imperative:  of reducing GHG emissions from whatever system is pursued, vs. continuing to ship 5,000 TPD of residential and commercial food waste to distant landfills.
As to Danâ??s concern about sewer overflows, that issue exists with or without disposers; the added flow from disposers is less than 1% per daily household water consumption/generation.  In mass balance terms, using NYC as an example, its WWTPs daily handle @ 1.3 billion gpd; if ALL 3 million homes had and used a disposer, the added flow would be perhaps 5 million gpd, or a de minimis impact â?? in the words of NYCâ??s study.
Kendall Christiansen

From: Anne Peters [mailto:annep@no.address] 
Sent: Thursday, February 28, 2008 6:52 PM
To: David Biddle
Cc: Dan Knapp; Kendall Christiansen; GreenYes@no.address
Subject: Re: [GreenYes] Re: Growing Global Interest in Food Waste Disposers
Good dialogue.
Note that the WSJ article, which I read, was not a glib endorsement but really 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 and heavily marketed here wth the post-WW2 housing boom - 50% mkt penetration now.  It never had much mkt in Europe but now is being positioned as a green strategy there as limits of successful backyard composting are being reached in places like Germany that have done it for a while. The article reports on a study by Carol Diggelman in '98 looking at 5 different ways of managing food waste, and concluded that disposals that fed to water treatment plants w/ CH4-to-energy 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 to see the discussion in that.

David Biddle wrote:

Kendall-I would love a copy of the WSJ article.

Dan- It seems to me that the problems that biosolid systems are having in this country are more a function of a dilapidated or under-sized infrastructure and that this issue calls forth the need to seriously examine that infrastructure. Also, in your climate backyard composting is probably a bit more doable than in northern climates like Philadelphia, Boston, Chicago, etc. In addition, in many cities people donâ??t have space, literally. Here in Philly the majority of backyards are postage size. Finally, in studies Iâ??ve seen, while the residential food waste component is high, the commercial and institutional fraction is much higher. Short of daily collection of roll-out carts, what is a Hilton Hotel supposed to do with their 2,000+ pounds of food scrap and sauces? 

Iâ??m advocating (and Kendall and I have talked about this often) for a very careful and thorough analysis of all the options for really solving this problem, especially for the commercial sectors. If it means that cities need to look at renovating with $200 million bond options or privatizing their sewer systems, or whatever, then so be it. Certainly, if the Bay Area is struggling the way you say it is, this process must already be underway. I would hope all the Waste-Heads their are looking to be a part of the solution. 

David Biddle, Executive Director
Greater Philadelphia Commercial Recycling Council
P.O. Box 4037
Philadelphia, PA 19118

215-247-3090 (desk)
215-432-8225 (cell)

on 2/28/08 4:16 PM, Dan Knapp at dr.ore@no.address wrote:
I believe that sewage treatment plants in the San Francisco Bay Area would not be enthusiastic about the WSJ's glib endorsement of garbage disposals to reduce 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 untreated 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 of the 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 conclusive 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 blockages not to mention lots of Biological Oxygen Demand. 

The best option is to compost food in your own backyard along with all the yard trimmings, food paper, and other organics such as cotton clothing.  I've done it for decades, and it's very satisfying, especially when combined with growing food in the enriched soil you get when you actually use the finished 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 humus.  I'm also taking carbon that used to be in the air and putting it into the soil, where it nourishes the soil critters and fungi that help plants grow.  The soil is much easier to work than the heavy clay that I had to start with; no clods at all, and it holds water like a sponge.

Next best is to use curbside food and yard debris collection; these centralized processing systems are proliferating all over the Bay Area right now. 

Dan Knapp
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:
On Tuesday, the Wall Street Journal featured a report about the growing international interest â?? with a focus on the EU â?? in the efficacy of food waste disposers (aka garbage disposals) as an environmental management tool, for immediate diversion of food scraps from the solid waste stream, and relying on wastewater treatment plants to process the solids in fertilizer products with energy recovery where possible.  In particular, it noted the experience of several cities that have intentionally opted for disposer-based systems for food scrap management.
Given that the WSJ remains subscription-based, if youâ??d like a copy of the article â?? as well as its Environmental Capital blog post on the same topic â?? please let me know and Iâ??ll forward.  If you would like access to one or more of the reports referenced in the article, let me know that, too.
Kendall Christiansen

Gaia Strategies

151 Maple Street

Brooklyn, NY 11225

o: 718.941.9535; cell: 917.359.0725

the writer is senior consultant on environmental affairs for InSinkErator, the leading manufacturer of residential and commercial food waste disposers, and former Chair of NYCâ??s Citywide Recycling Advisory Board


Stephan Pollard, Ph.D.-Environmental Dynamics
Cell: (479) 799-9190

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