[Stoves] Alternative to charcoal

Tue Apr 9 20:00:04 CDT 2013

Dear Dale,
the size and shape of the wood is important in a TLUD stove because
the fuel is lighted at the top and the primary air has to pass through
the biomass. Pieces of bamboo, stacked vertically in the fire chamber,
work quite well in such a situation. This solution is however not
available to stovers living in areas where bamboo is not naturally
available.
Yours
A.D.Karve

On Tue, Apr 9, 2013 at 2:39 AM, Andreatta, Dale A.
<dandreatta at sealimited.com> wrote:
> At the recent ETHOS conference Paul Means and Chris Lanning gave a very
> thought-provoking talk about an alternative to charcoal.  The basic idea was
> to use a gasifying stove with prepared wood fuel.  The prepared wood fuel
> would be bought by the user instead of charcoal, and the supply chain would
> be similar to charcoal.  The big advantage is that the very inefficient step
> of charcoal production is eliminated.  The stove would hopefully be easy to
> use and would smoke very little, so as to retain the benefits of a charcoal
> stove.
>
>
>
> Their proposed fuel was crumbled wood, which would work well, but seemed to
> me to require a lot of big machinery and capital.  How could one go from a
> tree to a fuel that would burn well in a gasifier with as little work as
> possible, and without too much costly equipment?  The fuel  should be as low
> or lower in cost than charcoal per unit of food cooked, and give a better
> ratio of food cooked per unit of tree.
>
>
>
> I did some preliminary experiments.  With 779 g of natural wood from the
> trees in my yard, I used a Paul Anderson Champion gasifier and boiled 5
> liters in 21.4 minutes (corrected).  After an easy light the stove burned
> steadily with no attention, other than turning down the primary air when
> boiling started.  About 10 minutes after boiling the pyrolysis ended and I
> transferred 123 grams of char sticks, glowing only weakly, into a charcoal
> stove, and continued simmering until nearly 2 hours after the start of
> boiling.  I had good turndown on the charcoal stove and a lid on the pot.
> There was a little smoke during the pyrolysis phase, but not too much.  This
> seems like excellent stove performance.
>
>
>
> Had I used a very good charcoal stove to perform a similar task, it might
> have taken 240 g of charcoal.  This would take about 1800 g of wood if the
> charcoal were made efficiently, or 3000 g if it were made normally.
> (Reference Means and Lanning on the efficiency of charcoal production.)
>
>
>
> The wood I started with was about 1 inch diameter (2.5 cm) by 6 inches (15
> cm) long, cut from my trees and dried outdoors but under cover for some
> months.  I didn’t measure the moisture content, but a previous oven-drying
> test with similar wood showed about 12-14% moisture.  A previous test with
> larger diameter wood didn’t go well, so I think this is about the maximum
> possible diameter.  I don’t know how long it took to get to this moisture
> content, not months I’m sure, but at least some number of days.
>
>
>
> The production method for this alternative to charcoal would be to use a
> chain saw to cut wood into convenient lengths while in the forest, then take
> it to a central place.  Here, use electric saws and/or hydraulic  splitters
> to cut the wood to the appropriate size.  Give the wood a modest amount of
> drying in the sun, or in some simple oven.  The wood might have to finish
> drying at the place of use.  I expect that split wood would dry faster than
> cut sticks, since the moisture doesn’t have to pass through the bark.
> Alternatively, use a chain saw and engine powered splitter to cut the wood
> to size in the forest, then transport to a central place for drying.  When
> fairly dry, transport the wood to the users as with charcoal.  During
> transport, the energy per unit weight would be lower than charcoal, but the
> energy per unit volume would be similar.  The user might be given the option
> of buying shorter sticks for cooking smaller meals, or longer sticks for
> larger meals.
>
>
>
> In comparing the economics of this method to charcoal, I would think of the
> cost of the fuel as coming from 5 elements; the cost of the trees, the cost
> of the processing equipment, the cost of the labor, the cost of the
> transportation and distribution, and the cost of the stove.  If the trees
> are free, then the fact that you don’t cut as many trees doesn’t help much.
> If the trees must be paid for, then this method looks more attractive.  The
> processing equipment for charcoal is virtually free, but hopefully this
> method doesn’t take too much equipment.  The labor for this method might be
> similar to charcoal, but it might be less because you are cutting and
> processing a lot fewer trees to serve the same number of customers.
> Transportation would be more expensive, since you are shipping more mass,
> though not a lot more volume.  This method would require a gasifier or
> T-Char stove, which would be an expense, though hopefully not a lot compared
> to the annual cost of fuel.
>
>
>
> Thus, if the trees must be paid for, this method might be attractive to the
> consumer of the fuel, the producer of the fuel, and to the forest.  If the
> trees are not paid for, this method looks less attractive, though the forest
> would still benefit and some outside subsidy might be available.
>
>
>
> Dale Andreatta, Ph.D., P.E.
>
>
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-- 
***
Dr. A.D. Karve
Trustee & Founder President, Appropriate Rural Technology Institute (ARTI)