[Stoves] sawdust stove

[K McLean]

Norm,

I am very excited about sawdust stoves. I have colleagues in Uganda, Kenya
and Malawi testing them.  Their testing is crude but uniformly successful.
In fact, the wife of one of them has completely stopped using charcoal and
is now only cooking with sawdust.  He says the stove burns for five hours
without tending.  There is smoke when starting but almost no smoke
thereafter, similar to charcoal. Their stove is 27 cm high and 26 cm
diameter

He also tested a stove 25 cm high and 21 cm diameter which works well.  It
cooked for just over 2 hours.

There are many websites that discuss making sawdust stoves out of used
gallon paint cans.  Metal paint cans are getting hard to find now in Africa
and Asia, though.  I tested sawdust in a gallon paint can with mixed
results.  I sourced my sawdust from a cabinet maker.  The sawdust is very
fine, like dust.  That may be my problem.  After packing the sawdust and
removing the pipe, the center hole held.  But the sawdust would not burn
without an external flame from below.  When the external flame was removed,
the sawdust smoldered until all of the sawdust turned to char.  The amount
of smoke was unacceptable.

[image: image.png]

This sawdust stove is built like a traditional rocket stove, with a hole on
the side.  Some of my colleagues prefer this design over stoves with the
hole in the bottom.  If the hole is on the bottom, the stove must be
elevated (eg, with bricks).

They have tested with many fuels and continue to test with more fuels and
fuel mixtures.  These fuels work, though none work as well as sawdust:
maize cobs, maize stalks, rice hulls, rice straw, banana peels, cassava
peels.  Some fuels like rice hulls cannot sustain a flame by themselves.
They need firewood or other fuel burning.  A single maize stalk burning
below the rice hulls does the trick.  Pine needles haven't worked in our
testing.

The stoves tend to emit very little smoke and they produce biochar.

A concentrator ring on top helps.

We are working on designs that will be affordable to even the poorest
families, $1-2.

I see great potential with sawdust stoves for shifting cooking fuel from
nonrenewable wood to renewable sawdust and crop waste.  My colleagues say
that where they live huge piles of sawdust can be found at sawmills and
even at carpenter shops.  There is no use for the sawdust so it is often
just burned.  I've heard the same about piles of rice hulls.

Sawdust stoves had been around for decades.  I don't know why they are not
ubiquitous.  I'm sure others on this list have experience with sawdust
stoves and can explain what is a conundrum to me.

Kevin McLean
Sun24

On Tue, Jan 12, 2021 at 1:46 PM <ajheggie at gmail.com> wrote:

> A message from Norm Baker which was too big for the list so I resized
> the pictures
>
> Andrew
>
> Gentlemen;
>
> Out of simple curiosity I built a sawdust stove. In nearly 15 years of
> messing with TLUDs I had never heard of a sawdust stove, so I followed
> the original publication and constructed one from a 7 gallon popcorn
> can. Took about 15 minutes for construction. Here is what I found of
> interest;
> a. First, I dried the red Alder sawdust from a local lumber mill over
> electric heat and I know the moisture content was less than 10%.
> b. It is a touchy stove. Even when I firmly packed the dry sawdust,
> the sawdust was very susceptible to collapsing inward on the central
> hole when the pipe was removed.
> c. It smoked for the entire burn.
> d. Interestingly, the smoke had the turbulence seen in a flame cap
> kiln and rolled over the edge of the popcorn can and into the flame. I
> could tell much of the smoke was consumed but not nearly enough.
> e. As the sawdust was consumed, after flames cover the entire
> horizontal surface of the sawdust, the char started combusting and the
> translucent blue flames were easily visible around the edge of the
> stove.
> f. Touching the stove in any fashion, resulted in a surprising amount
> of sparks in the exhaust stream. These sparks or fireflies went as
> high as 10 foot up into the air before being extinguished in the air
> or on wet vegetation nearby.
> g. I was surprised that the stove had a 2 1/2 hour burn time on four
> kilograms of sawdust.
>
> All in all, an interesting stove, but not one I would recommend anyone
> start using. The amount of smoke and hot sparks are simply
> unacceptable.
>
> Norm
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