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[GreenYes] Whither/WhettherToronto's Sludge?


An excellent source of continuing education about the production and
beneficial use of biosolids (the material formally known as sewage sludge)
is the National Biosolids Partnership (, a partnership
between EPA, the Water Environment Federation, and many
states/municipalities...In addition to its excellent website, NBP's weekly
e-newsletter is a good place to start; it doesn't shy away from dealing with
the complexities and occasional controversies re biosolids.

A recent one included a discussion of Toronto's problem in the context of it
entering into a research partnership w/DC's wastewater management its search for ways to improve its options.

My lay-understanding of Toronto's problem is that a) its biosolids don't
meet sufficient quality standards (yet) for optimal marketing of them (which
is why they've been landfilled), and that b) Canada's climate inherently
limits field application of quality biosolids to certain times of the year
(i.e., when the ground isn't frozen).

By contrast, an increasing percentage of biosolids in the U.S. is
beneficially reused (probably two-thirds or more), most often via various
forms of compost and/or fertilizer -- with increasing interest in
energy-related opportunities (not just burning, but actual production of
liquid fuels)....In NYC's case, for example, what used to be ocean-dumped
until 1992 is now 100% beneficially reused, with 70% meeting Class A (EPA)
standards and over 50% processed locally into fertilizer pellets that are
successfully marketed to orange groves in Fl, etc. Some percentage is
actually used locally -- for ballfields, roadsides, etc. And a supplemental
benefit: system costs for biosolids production and transport to markets
have decreased substantially -- from over $100M initially to mid-$50M's at
present, and been stable for several years.

Also worth noting is Toronto's continuing challenges with the compost
generated via its green-bin program....processing, quality, markets, etc. --
as well as costs.

The subtle point is this: in U.S. cities/municipalities, most food waste is
actually diverted from the solid waste management system via the use of food
waste disposers (given that it's 70% water, it's more liquid than solid)
which use the sewer system to transport organic waste (human + food) to
wastewater treatment plants for processing....with the premise that the
additional food waste actually improves the quality of biosolids. Not only
does a food waste disposer/WWTP system eliminate truck-based collection
costs and environmental impacts, it also improves methane recovery, rodent
and odor control, etc....

In Philadelphia, for example, commercial food waste disposers are required
as a condition of obtaining a dumpster permit for a restaurant so as to
eliminate organic waste from them....

And, given the choice, I'd much rather trust wastewater engineers with
managing food waste than solid waste engineers/managers with their focus on
compaction, transport, dumping/burning and more compaction.

Glad to discuss off-line, including the issues in Toronto and its
surrounding cities -- which all are struggling with the same issues -- and
point you to dozens of recent studies from around the world that carefully
examine these issues, including assessing the life-cycle impacts of various
systems for managing food waste....they all concur that food waste
disposer-based systems create manageable impacts for well-managed wastewater
treatment systems, while offering significant environmental and economic

While I know full well that food waste disposers are considered a
"third-rail" issue for some, in the U.S. they are a fact of life -- the
majority of U.S. homes have them (for decades), and installed in probably
more than 80% of new homes...with growing acceptance internationally, as
nations/states/cities struggle with how best to manage food waste and
address GHG issues.

Thanks for considering...

Kendall Christiansen
Gaia Strategies

The writer has seventeen years experience in solid waste management and
recycling systems in NYC -- including chairing NYC's Citywide Recycling
Advisory Board for 5+ years -- and serves as senior consultant on
environmental affairs to InSinkErator, the leading manufacturer of food
waste disposers. (

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