Stovers,
I really like Lanny's explanation and the photo (photo in original
message). Wood that is cut to an appropriate length (a known length
for a specific type of stove) and then split (or split and then cut into
desired lengths).
I will call this "split-wood," to help distinguish it from cord-wood or
wood chips or stick-wood.
I learned from Ugandans to place split wood vertically into TLUD
stoves. Fill it well; not just a couple of loose pieces.
Some data and photos about this are in the Quad 2 Stove Performance
Report <http://www.drtlud.com/2012/10/23/quad-2-stove-performance-report/>
found at http://www.drtlud.com/2012/10/23/quad-2-stove-performance-report/
Shows 3 different sizes (thickness) of the same wood used. Split-wood
works great, and the resultant char is in good-sized chunks.
One difference from Lanny's report (that is based on USA experiences) is
that in many developing countries,
a. most of the wood seems to be branch size, not trunk size.
b. chain saws are not so easily accessible
c. bow-saws for cutting are available, but not necessarily affordable
to all. But in addition for a machete (panga), or an axe, a bow-saw
is the start of making "prepared fuels" or "processed fuels".
Split-wood is not as "prepared" as wood chips, or pellets, or alcohol or
LPG, but split-wood is more prepared than gangly branches dragged in
from the hillside and stuffed into 3-stone fires.
There is still a lot of work to be done about fuel supplies.
Paul
Paul S. Anderson, PhD aka "Dr TLUD"
Email: psand...@ilstu.edu Skype: paultlud Phone: +1-309-452-7072
Website: www.drtlud.com
On 4/9/2013 10:29 AM, Lanny Henson wrote:
Dale and Stovers,
How about wood cut to a length, that works for a typical household
stove, maybe 3 to 6" long, it could be a large diameter or a small
diameter, and let the end user split the wood to the right size for
their stove, with a hatchet.
Wood dries quicker when cut to a shorter length and it is easy to
split, easy to handle, and easy to weigh, and the wood is more compact
to ship, also the wood dries quicker.
I have been burning red oak, pallet oak, spruce 2x4 and limbs cut to
about 6" long, and split to size with a hatchet. I used a chain saw
for the disk and a hand saw to cut the limb and 2x4. If the wood is
longer than you need, and you do not have a chain saw, split the
wood first and then use a hand saw to cut it to length. I usually cut
a typical "fire wood" length in 3 pieces.
Wood, Short Lengths, Split to Size.
Lanny
----- Original Message -----
*From:* Andreatta, Dale A. <mailto:dandrea...@sealimited.com>
*To:* Discussion of biomass cooking stoves
<mailto:stoves@lists.bioenergylists.org>
*Sent:* Monday, April 08, 2013 5:09 PM
*Subject:* [Stoves] Alternative to charcoal
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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