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

[Tom Miles]

Dean,

I understand your intent and appreciate your good work. I like the direction
but we still need to apply rigorous testing and evaluation criteria so that
the results are meaningful. 

I'm not too concerned about where the rocket falls. It may perform well
under many conditions. I am concerned that if we are generating information
about emissions that it be as close to actual use (e.g. CCT, KPT) conditions
as possible. And the performance conditions should be well documented. Our
purpose should be to find the best point of performance of these stoves and
encourage their use in those conditions. That may actually require different
types of fuels, densities and moisture contents for different stove designs.
Charcoal testing should include improved stoves like the New Lo Trau.

In my experience very dry fuels make more CO. Wet fuels make more PM. We
need to narrow the gap between the artificial environment of kiln dried fuel
and fuel that is conditioned (humidified) to simulate fuels in actual use.
The 3.6-4% MC fuel you used corresponds to fuels stored for a long time in a
dry inside environment (60F 15% relative humidity). That's about the same
equilibrium moisture content (EMC) as furniture in a house. I have hundreds
of analyses of rice husks from thousands of tons that I have burned, mostly
in Thailand. I have never burned rice husks as dry as 4%. With the weather
today in Bangkok, Manila or Phnom Penh (80F, 79% RH) the rice husk EMC would
be about 16% MC. With higher moisture CO will come down. PM may increase.
Your previous "benchmarks" may all move up.      

Previous tests on heating stoves have been done using 18% MC and 35% MC.
15%-18% is typical of air dry wood. 35% is representative of partially air
dry green wood. Your 10, 20 and 30% MC tests will fall somewhere in between.
We look forward to the results. Hopefully the tests will include references
to similar tests on heating stoves.  

If there is more information about the performance tests of the six stoves
then it should be referenced in the study cited. I didn't see a reference or
link to the detailed test data which should include information not reported
in your summary.

I appreciate that these tests take time and resources. As we have discussed
before we need to have more labs around the world doing these tests. I do
not know what funding is available for this kind of testing but we should
have more of it. At ETHOS 2006 EPA's Jim Jetter described proposed testing
but we have not seen any results.

I invite everyone to suggests ways that we can improve testing so that the
results can be more representative of actual use.

Regards,

Tom  




   

> -----Original Message-----
> From: owner-ethos at vrac.iastate.edu [mailto:owner-
> ethos at vrac.iastate.edu] On Behalf Of Mr. Dean Still
> Sent: Tuesday, October 09, 2007 1:44 AM
> To: Discussion of biomass cooking stoves
> Cc: 'Discussion of biomass cooking stoves'; methods at bioenergylists.org;
> ethos at vrac.iastate.edu
> Subject: [ethos] Re: [Stoves] Laboratory Comparison of the Global-
> Warming Potential of Six Categories of Biomass Cooking Stoves
> 
> 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