[Stoves] Between PM 2.5 and PM 10

Sun Jun 9 12:10:44 CDT 2013

Hi All,

As seen in the Jetter graphs, fan stoves like the Oorja and Philips
produced more fine particles compared to the natural draft TLUD which was
low in ultra fine particles. The new IWA tests require filter measurement
of PM so ultra fine particles are captured and counted. Particle color can
also be seen on the filters. Sometimes blond particulate matter
predominates in fan stoves which is interesting. We think that cooling the
combustion decreases black particulate matter but we're continuing to
investigate how to remove as much black as possible. It does seem that
tuning the stove changes the rate of production of color, ultra fine, and
larger particulate matter.

Best,

Dean

On Sun, Jun 9, 2013 at 8:12 AM, Julien Winter <winter.julien at gmail.com>wrote:

> Dear Crispin and stovers;
>
> RE: Just, B; Rogak, S; Kandlikar, M (2013) Characterization of
> ultrafine particulate matter from traditional and improved biomass
> cookstoves.
> Environmental Science & Technology  47: 3506-3512   Doi: 10.1021/Es304351P
>
>
> The article abstract I posted is certainly a teaser for those with a
> keen interest in this area.  Crispin posed some questions about the
> abstract that I will try to answer below:
>
>
> The cookstoves they tested were (1) a 3-stone fire, and (2) the
> “Chulika” rocket stove (distributed by iSquareD, Bangalore, India),
> both burning sticks of hemlock; and (3) the fan-powered  “Oorja,” TLUD
> stove (First Energy Ltd., Bangalore, India) burning commercial wood
> pellets
>
>
> > Something that is not clear from the abstract is whether the 'increase'
> in
> > particles is an increase in the number of particles or an increase in the
> > mass of particles, or an increase in the mass of small particles.
>
> Number of particles.  Over a range of 15 to 660 nm particle diameter,
> they measure the number of particles per unit volume of air, as a
> proportion of the mass of carbon emitted during their period of
> measurement to produce a graph of number of particles vs. particle
> diameter.  The instrument was a TSI Scanning Mobility Particle Sizer
> (SMPS) model 3080 with a custom differential mobility analyzer (DMA).
>
>
>
> > " The 3-fold increase in quantities of sub-30 nm particles from improved
> > cookstoves warrants further consideration by health scientists, with due
> > consideration to the higher combustion efficiencies of improved
> cookstoves."
>
> My interpretation is that there are trade-offs to be considered by
> health scientists.  The efficiency of combustion increased from
> 3-stone < rocket < TLUD, (I suspect due to higher and more uniform
> temperatures at the site of combustion in the TLUD compared to other
> stoves), but there was a decrease in the size of particles emitted.
> The increase in efficiency is good, because there is less fuel used
> (fewer trees cut, less time gathering wood, less time cooking and
> attending the stove), and a lower total mass of particles emitted.
> Unfortunately, along with increased efficiency came a shift in the
> spectrum of particle sizes emitted from larger soot particles that are
> trapped in respiratory tract mucus, to nanoparticles that can make it
> into the blood stream.  The dosage -- or concentration in the kitchen
> atmosphere -- of particle sizes from various stoves has to be
> considered along with changes in toxicological risk associated with
> various particle sizes.  The health risk associated with nanoparticles
> from combustion of biomass needs more research.  When all trade-offs
> are considered, a better nutrition and quality of life may come from
> using improved cookstoves, even though they may pose a new set of
> health risks down the line.
>
>
> > What does 'quantities' mean, exactly?
>
> 'Quantities' is vague language that seems to have escaped the
> reviewers.  My interpretation is that 'quantities' is 'concentration
> of particles', analogous to dosage.  '3-fold' is a rough abstraction
> of their findings, because they are dealing with continuous gradations
> of particle sizes.
>
>
>
> > "Particles from improved stoves formed clearly defined chain agglomerates
> > and independent spheres with little evidence of volatile matter ..."
>
> This they observed using an electron microscope.  That paper gives
> some pictures that show the particles from 3-stone fires to be much
> larger and clumped than particles from the improved cookstoves.  The
> particles from the improved cookstoves appeared more dense than
> 3-stone particles.  Since they measured a higher proportion of
> elemental carbon in particles from improved cookstoves than 3-stone
> fires, they reasoned that the particles emitted from 3-stone fires
> contain more partially combusted volatile matter.
>
>
> > This is extremely important to me - the lowering of volatile matter
> > condensing into particles. The stove burning cleanly means getting rid of
> > (by burning or not forming them) condensed volatiles. The health
> > consequences from this fraction is far high than 'dry dust' though I
> > understand that investigations of the ultra-fines are not nearly
> > completed/understood.  Ultrafine particles (UF) are well distributed
> > throughout the atmosphere so we have been living with the impact of them
> for
> > a long time. Perhaps we will find BC UF is really bad for us, maybe not.
>
> That is an interesting point that there is a natural background of
> untrafine particles.  A question, though, is about how they were
> formed, their chemical composition, and our level of exposure.  UF
> particles from biomass fires are what we have evolved with, especially
> if fire was domesticated by Homo erectus.
>
> > Cigarette smoke is full of condensed volatiles so it is interesting to
> me to
> > know if the comparison of PM emissions per se are 'equal to' cigarette
> smoke
> > or akin to cigarette smoke, or not nearly as bad as cigarette smoke. It
> is
> > quite possible that condensed volatiles from evaporated coal (which
> > constitutes a lot of the emissions of an igniting coal fire in a poorly
> > constructed stove - maybe 90%) are a bad as cigarette smoke. The main
> point
> > is that the particles are not from combustion, not from almost the
> complete
> > lack of it! Roasting fuel is a major source of PM. Cooling a flame
> against a
> > cold surface produces PM of a very different nature.
>
>
> > Thanks
> > Crispin
>
>
> For anyone interested in more details, I suggest that they get a copy
> of the paper which can be purchased if need be.  The authors can be
> found at The University of British Columbia, Canada, were I believe
> Brian Just did this work for his M.Sc., supervised by Steve Rogak
> (Mechanical Engineering Department) and Milind Kandlikar (Liu
> Institute for Global Issues).
>
> Regards,
> Julien
>
> --
> Julien Winter
> Cobourg, ON, CANADA
>
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