[Stoves] Laboratory Comparison of the Global-Warming Potential of Six Categories of Biomass Cooking Stoves

Tue Oct 9 04:44:26 EDT 2007

Hi Tom,

I'm in India trying to make great, inexpensive stoves so this will be
short because the net seems to drop out whenever I write a long message.

Haven't we discussed that in response to these questions we sponsored a
woman from Cameroon to spend a couple of months at the lab? She did a very
long series of experiments with various stoves using wood at 10, 20, 30%
moisture content. She looked at fuel use and emissions. This study should
be out soon.

We are not doing anything to favor the rocket, Tom. I think it odd that
you would suggest it. As it turns out the rocket, gasifier, and fan all
were improvements. The fan stove was amazing. I have to say that our lab
takes advice to heart, we respond by studying the question, which takes
time and great effort. The questions you and Crispin raised at ETHOS are
being addressed through experimentation which will hopefully give us
answers. We encourage everyone to do research as we do.

All Best,

Dean

On Tue, October 9, 2007 12:25 am, Tom Miles wrote:
> All,
>
>
> My impression on reading this work is that it is an impressive first test
> of a series of methodologies but I think the results suffer from the same
> problems we have discussed previously with the UBC WBT. While the tests
> as used by Aprovecho may show relative differences between stoves for the
> same fuel (7% MC Douglas Fir), when applied to emissions fuels should be
> used that are appropriate to the stoves being tested. I very much doubt
> that even fuels of the same density as douglas fir are burned at 3.4% MC.
> (We have
> discussed here the need to look at emissions at 15% MC and 35% MC with the
>  same stove to test performance with more commonly used moisture
> contents.) I also seriously doubt that rice hulls are actually burned at
> 4% MC. The very
> low moisture would show much higher CO levels in various stove types than
> probably actually occur. This leads me to believe that the performance of
>  these stoves is misrepresented by the tests and therefore the emission
> data is useless. What is the best performance of each of these stoves;
> what are the conditions that cause that performance; and, how does that
> compare with the performance reported here? How is it that the stoves are
> compared under circumstances that seem to favor the rocket design?
>
> We have questions of methods and results to settle. Let's go back and
> compare the performance of the stoves in these tests with a range of
> performance parameters before drawing conclusions about performance and
> emissions. The questions raised in the January PCIA and ETHOS meetings
> are still unanswered.
>
> Perhaps those many coauthors of this report (Bond, Macarty, Ogle, Roden,
> Still and Willson) can show us how the performance reflected in this
> report compares with previous tests and more typical fuels.
>
> Let's use discussion of this study as a vehicle to resolve these issues.
>
>
> Thanks
>
>
> Tom
>
>
>
>
> -----Original Message-----
> From: stoves-bounces at listserv.repp.org
> [mailto:stoves-bounces at listserv.repp.org] On Behalf Of Tom Miles
> Sent: Monday, October 08, 2007 9:01 AM
> To: 'Discussion of biomass cooking stoves'
> Subject: [Stoves] Laboratory Comparison of the Global-Warming Potential of
>  Six Categories of Biomass Cooking Stoves
>
>
> Laboratory Comparison of the Global-Warming Potential of Six Categories
> of Biomass Cooking StovesNordica MacCarty, Damon Ogle, Dean Still, Dr.
> Tami
> Bond, Christoph Roden, Dr. Bryan Willson, September 2007
>
>
> Abstract
> Improved cooking stoves have been shown to reduce the amount of fuel used
> to cook food and the air pollution produced in kitchens. Reducing
> deforestation and smoke inhalation have been the primary motivating
> factors for the dissemination of improved cook stoves. Recently, the
> potential of improved stoves to reduce the effects of biomass combustion
> on global warming has become a major interest, as well.
>
> Gaseous and particle emissions from six cooking stoves were analyzed: a
> three-stone fire, a rocket stove, a fan stove, a gasifier stove, a
> charcoal stove, and a rice-hull burning stove. These stoves were chosen to
> highlight different methods of combustion. Results indicated a significant
> difference in emissions between the stoves when the overall
> climate-forcing effects were calculated as CO2 equivalents on a 100-year
> timeframe, known as Global Warming Potential, or GWPi
> <http://www.bioenergylists.org/en/taxonomy/term/1287> .
>
>
> Overall data showed that as much as a 50% reduction of fuel use, air
> pollution and GWPi <http://www.bioenergylists.org/en/taxonomy/term/1287>
> can be achieved by three of the wood-burning stoves in comparison to a
> carefully-tended laboratory three-stone fire. The rocket and fan stoves
> produced 39%, a gasifier stove 56%, and a charcoal stove 84% of the three
>  stone fire's global warming potential when CO2 is included. If the fuel
> is harvested sustainably, then the CO2 is reabsorbed by the replacement
> biomass, and can be carbon neutral. In this case, only the products of
> incomplete combustion (PICi
> <http://www.bioenergylists.org/en/taxonomy/term/322> ) are considered.
>
>
> When fuel is harvested sustainably the rocket stove produced 41% of the
> warming potential of the three stone fire, the gasifier 29%, and the fan
> stove a remarkable 4%. The burning of charcoal produced 61% more warming
> emissions than the three stone fire, not counting the energy loss or
> emissions made when making the charcoal. Products of incomplete
> combustion (PICi <http://www.bioenergylists.org/en/taxonomy/term/322> )
> contributed from 26% to 51% to the overall Global Warming Potential
> produced by the direct burning natural draft stoves. Estimates of carbon
> reductions based on fuel use alone may not be accurate if PICs are not
> measured, especially if the fuel is harvested sustainably.
>
> Measurements were based on the specific emissions, or grams of emissions
> produced per liter of water boiled and simmered. In this way, heat
> transfer efficiency is taken into account along with the combustion
> efficiency. It is important to consider that these results were from
> laboratory testing field results will differ and be highly variable. The
> intent of the investigation was to assess the performance of the stoves
> when operator-influence was minimized in order to better understand the
> capability of each type of stove technology.
>
> See articles at: http://www.bioenergylists.org/en/gwpapro0907
>
>
>
>
> Tom Miles
>
>
>
>
>
>
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