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 The actual costs for the two systems would be out of date, but I’ll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
email@example.com [mailto:firstname.lastname@example.org] On Behalf Of Helen Spiegelman
Sent: Tuesday, January 29, 2008
To: Jeffrey Morris;
email@example.com; firstname.lastname@example.org; 'Gillespie Gerry';
email@example.com; firstname.lastname@example.org; email@example.com;
Subject: [ZWIA] Re: LA Zero Waste
Apologies for cross-posts... it's hard to know who's on which list
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?
At 10:24 AM 1/29/2008, Jeffrey Morris wrote:
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
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://22.214.171.124/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.