Using in-sink food disposals (in this article called garburators) can
be a divisive issue. In fact, the City of Vancouver is currently
debating whether to ban their use due to the excess strain that food
waste (which has a much higher organic loading than sewage) puts on the
sewage treatment plant. A common question is whether it is better to
send food waste to the landfill or sewage treatment plant. The obvious
answer is neither (compost and anaerobic digestion are much better
options); it is a no-win decision between the landfill and treatment
plant, as both options have major downsides.
However, Insinkerator, a major manufacturer of disposals, has been
pushing that disposals are a sustainable option for processing food
waste. Their rationale is that anaerobic digesters at the treatment
plant treat the food waste that is sent to the plant via disposals.
While this will make disposals more sustainable than without a digester,
most sewage treatment plants in this country do not have a digester.
Furthermore, those that do often treat the sewage sludge that results
after the aerobic treatment process has already occurred, meaning it is
still an energy intensive process, even if offset with biogas. Also, by
digesting food waste with sewage, the resulting fertilizer can be
contaminated and unsuitable for food crop production. One option that
is touched on in this article, is to have several disposals flow to a
centralized vat that is then used as a feedstock slurry for digestion.
While this would be most appropriate for commercial operation, there may
be potential for this in high-density residential housing areas, where
composting is also more difficult. I believe the in-sink food disposal
can play an important role in solving food waste, especially for on-site
small scale anaerobic digestion.
Have a great weekend,
Metro Vancouver enters garburator food waste debate
The Globe and Mail
September 15, 2014