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

Title: Re: [GreenYes] Re: Growing Global Interest in Food Waste Disposers
Kendall mentioned a couple of papers authored by Diggelman.  They are:

Diggelman, C. and R. K. Ham (2003). "Household food waste to wastewater or to solid waste? That is the question." Waste Management & Research 21(6): 501-514.

    Decision makers need sound analyses of economic and environmental impacts of options for managing household food waste.  Food waste impacts public health (it rots, smells, and attracts rodents) and costs (it drives collectionfrequency).  A life cycle inventory is used to quantify total materials, energy, costs and environmental flows for three municipal solid waste systems (collection followed by compost, waste-to-energy or landfill) and two wastewater systems (kitchen food waste disposer followed by rural on-site or municipal wastewater treatment) for food waste management.  Inventory parameters are expressed per 100 kg of food waste (wet weight) to place data on a normalised basis for comparison.  System boundaries include acquisition, use and decommissioning.  Parameters include inputs (land, materials, water) and output emissions to air, water and land.  Parameters are ranked simply from high to low.  Ranking highest overall was the rural wastewater system, which has a high amount of food waste and carrier water relative to the total throughput over its design life.  Waste-to-energy was second; burning food waste yields little exportable energy and is costly.  Next, municipal wastewater tied with landfill. Municipal wastewater is low for land, material, energy and cost, but is highest for food waste by-product (sludge).  Landfill ranks low for air emissions and cost.  Compost ranks lowest; it has the lowest material and water inputs and generates the least wastewater and waterborne waste.

Diggelman, C. (1998). Life-cycle comparison of five engineered systems for managing food waste. Madison, University of Wisconsin. Doctoral Dissertation.  Call Number AWB D5727 C376

If you go to your nearest library you can probably request a copy of the dissertation be sent you using Interlibrary Loan.



Kendall Christiansen wrote:

Per Anne’s comment/request, at you will find six contemporary studies – beginning with the UWisconsin study (’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 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 – by topic, to make it easy to find particular answers – 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 – and have done so for decades.  After all, not much difference between food and human waste – both @ 70% water, with similar chemical composition.   Plenty of studies of impacts/benefits re wastewater treatment systems, but there’s also substantial evidence in the form of the ‘wisdom of crowds’ of nearly all municipalities in the U.S. having chosen to allow disposers for decades.  Dave Biddle’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 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 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 Dan’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 – in the words of NYC’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 don’t have space, literally. Here in Philly the majority of backyards are postage size. Finally, in studies I’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?

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 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 – with a focus on the EU – 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 you’d like a copy of the article – as well as its Environmental Capital blog post on the same 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, 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 NYC’s Citywide Recycling Advisory Board


Untitled Document

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

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