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[GreenYes] Re: Whither/WhettherToronto's Sludge?



At 09:12 AM 7/9/2006 -0400, Kendall Christiansen wrote:
>[....]
>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.

This is interesting. A couple of concerns/questions:

Adding food waste to the sewer system mixes it with the metals and
other toxins in the system, limiting downstream uses--as of the sludge.

To the extent that the stuff is fully oxidized to CO2 in the sewer
plant--presumably the plant is trying to do this to minimize oxygen
demand of the effluent--I would think that the organics are largely
being wasted, while contributing to climate change.

To the extent that the stuff is feeding the bugs and getting
incorporated into the bacterial biomass in the sludge, it would seem
that the "problem" is just being moved around (with the contamination
issues added).

On the other hand, if the food waste is collected separately, and
composted, or digested anerobically, the outcomes would seem more
positive--we are getting a useful soil amendment and maybe some
useful fuel gas. (Much of the carbon will still end up in the
atmosphere, but maybe while doing more good along the way....).

But I am only thinking about this qualitatively...would be
interesting to see a real analysis of alternatives.

am

Alan Muller, Executive Director
Green Delaware
Box 69
Port Penn, DE 19731 USA
(302)834-3466
fax (302)836-3005
greendel@no.address
www.greendel.org


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