Jeff ~
From what you say, the environmental case for MBT rests on 100%
stabilization ("no methane"). This assumes that it's a wash for
embodied carbon, since both WTE and MBT/landfilling essentially write off
embodied carbon, while even small fugitive emissions of Ch4 will put the
GHGs from MBT-treated residuals higher than CO2 emissions from WTE.
THe case for MBT over incineration may rest on the system's flexibility
(ability to reduce throughput as diversion improves), as well as capital
costs.
I just downloaded a
report
by
Golder & Gartner Lee, done for Niagara Region (where Nova
Scotia's Barry Friesen now works) that concludes MBT better choice than
WTE. I haven't read it yet.
H.
At 12:00 PM 1/29/2008, Jeffrey Morris wrote:
Helen,
It?s fairly straight forward. If MBT produces a product that will
generate no methane when landfilled, then the MBT + landfill combo most
likely will have less GHG emissions than incineration + ashfill, even
after deducting the GHG offsets from natural gas fueled electric power
generation. The MBT system itself would generate some GHGs to run
equipment, so I would need to know those emissions to produce actual
numbers for the comparison. But my intuition is that the equipment
and operations for incineration plus the amount of fossil fuel content of
products that are incinerated have a greater GHG impact than the
additional GHG from MBT equipment and operations.
Same result for all the other environmental impacts in addition to
climate change.
Then, if MBT + landfill costs less than incineration + ashfill, it?s a
slam dunk that MBT for the residuals is better than incineration with
energy recovery. This, by the way, was the conclusion of that study
that we did for Halifax in the early 90s that resulted in the MBT system
they have in place there. The actual costs for the two systems
would be out of date, but I?ll bet the cost ratios of the two are still
about the same. So you could check out those studies to get a quick
fix on the margin of additional cost imposed by the incineration +
ashfill alternative.
Best of luck ? you should know that there was at least one representative
from Vancouver at the Recycling Council of Ontario?s Energy from Waste
forum in November of 2006. I gave the keynote and talked about the
cost benefits of landfill versus incineration for disposal of residuals
(given that their overall environmental impacts were about the
same). My impression was that the Vancouver folks were already well
down the road to pushing incineration as their MSW disposal
alternative.
Jeff
From: zwia@no.address
[mailto:zwia@no.address]
On Behalf Of Helen Spiegelman
Sent: Tuesday, January 29, 2008 11:36 AM
To: Jeffrey Morris; matt@no.address; eric@no.address;
'Gillespie Gerry'; ricanthony@no.address; zerowaste_sd@no.address;
zwia@no.address; gaia-zero-waste@no.address;
GreenYes@no.address; crra_members@no.address
Subject: [ZWIA] Re: LA Zero Waste pans
Importance: High
Apologies for cross-posts... it's hard to know who's on which list
above.
Jeff, have you run MBT through your calculator? Here in Metro Vancouver
we are being told that WTE is the best solution for "residuals"
that have been subject to 70% diversion through composting (food, yard,
contaminated paper) and recycling. Can we make a case that investment in
MBT for the remaining 30% is a better idea than investment in
WTE?
Helen.
At 10:24 AM 1/29/2008, Jeffrey Morris wrote:
Hey Everyone,
Many of you have obtained the model/calculator for the environmental
benefits of recycling and composting from me. Because of the great
dialogue on composting versus incineration on these list serves, I
thought I should mention again that the model does include in the
environmental benefits of composting the upstream pollution prevention
from reduction in the use of synthetic fertilizers and pesticides, and
the carbon sequestration benefits of compost applications and the
resultant healthier soils and plants.
The version I sent around assumes that compost use offsets 50% of the
average level of synthetic fertilizer and pesticide use on home lawns and
gardens. The model can calculate any level of offset between 0% and
100%. The model also takes into account the build up of carbon in
the soil from the use of compost, both as a result of the addition of
carbon in the compost itself and as a result of the increased humus
formation as a result of better plant growth.
I picked the 50% fertilizer and pesticides offset estimate based on the
observation that someone who buys compost for their lawn or garden is not
likely to continue to buy the same amount of synthetic fertilizers and
feed/weed type of products. One might argue that the offset should
be higher. My usual tactic in the calculation of environmental
benefits is to make assumptions that are if anything biased toward the
burn or bury proponents. The results still come out favoring
recycling and composting, and it?s then hard to make the case that my
analysis is biased toward recycling and composting. However, one
could run the model at 100% offset of synthetic fertilizers to see how
much additional benefits accrue from going totally green!
The offset assumption for pesticides is also 50% in the baseline
model. Some of this is from the reduction in purchases of synthetic
fertilizers that include herbicides (weed ?n feed products). Some
is from the reduced need for herbicides and pesticides due to the
stronger plants that result from a natural lawn and garden care
approach.
The carbon build up estimate is from EPA/s WARM model and the supporting
document Solid Waste Management and Greenhouse Gases: A Life Cycle
Assessment of Emissions and Sinks (3rd edition, Sept
2006). The synthetic fertilizer and pesticide offsets are based on
a study that an economist at Seattle Public Utilities, Jenny Bagby, and I
did on backyard composting and natural lawn and garden care. That
study has been peer reviewed and accepted for publication in the
International Journal of Life Cycle Analysis. The article is
published online awaiting its turn in the queue for publication in the
printed journal. The abstract can be found at
http://82.98.75.226/sj/lca/abstract/doi/lca2007.07.350
.
One other point ? the model includes other environmental benefits in addition to climate change benefits from recycling and composting. It?s important to remember that human toxics and carcinogens, ecosystem toxics, acid rain, smog, ozone depletion, habitat alteration, species biodiversity, and water nitrification impacts are also reduced by recycling and composting. In total these other impacts are of at least equal if not greater importance than climate change.
Many thanks and much appreciation to those of you that are out there everyday promoting clean and green behaviors. At some point we?re bound to reach a tipping point away from our chemically drowned lifestyles.
Best wishes,
Jeff
|