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Hello BESTers,

  This article discusses an interesting but I believe erroneous 
idea.  It claims that using households food waste disposers is a 
"green" method of handling food waste.  The argument is that 
sewage treatment plants which receive the ground-up food waste is 
using anaerobic digestion to generate biogas and biofertilizer 
from the waste.  This sounds almost too good too be true, 
especially since most of us already have a food waste disposer in 
our house, but I'm afraid this argument is over-stated.  While 
certainly there are treatment plants using anaerobic digestion to 
capture energy, they are a very small minority.  The article 
states that insinkerator.co.uk claims that 60-70% of treatment 
plants in the UK use anaerobic digestion (a minority of plants use 
AD in the US).  However, just because a plant is using AD does not 
mean it is capturing energy.  In fact the vast majority of those 
that are using AD in the US simply flare the gas.  This does 
nothing to offset the high energy demand to treat the waste in the 
plant.  In addition, plants that use AD are treating the waste 
activated sludge not the raw sewage.  Meaning the food waste must 
still go through the energy-intensive aerobic process prior to 
generating this sludge.  On top of that food waste has an organic 
strength roughly 500-1000 times that of sewage, which takes even 
more aeration energy to treat.  With all that said, I agree that 
if a treatment plant to treating the raw sewage anaerobically and 
using the biogas for energy production, that food waste disposers 
are an excellent option for disposing food waste, but I'm afraid 
this idealistic vision is just not true for the large majority of 
municipalities in the US.  In the mean time, I believe composting 
and vermicomposting are currently the best option outside of true 
food waste digestion.
As always any responses or rebuttals are welcome on the 
listserve.

Have a great weekend,
Ryan

http://www.guardian.co.uk/environment/2010/oct/17/not-easy-being-green-food-waste-anaerobic-digestion-landfill

Can I throw out food and be green?
Lucy Siegle
The Observer
October 17, 2010