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Piet,
In our part of the world (East Africa), the use of
sawdust in uncarbonised form comes up against basic economic constraints. As an
example, we had an NGO making sawdust briquettes in Isiolo, a large town in the
drylands of northern Kenya ('SALTLICK'). They used reject grade gum arabic
(Acacia senegal) as the binder and the work was done as a cottage industry using
manual presses. The dried fuel briquettes had an energy content of 18 MJ/kg vs.
about 16 MJ/kg for dry firewood. Yet their retail price was approximately the
same as that of charcoal, which has an energy content of over 30 MJ/kg, due to
the labour required to source the raw materials, mix them and operate the
presses (vs. firewood collectors who wander into the bush and cut what they
like). That comparison basically spelt the demise of the project. You can't
sell something at the price of charcoal when it has roughly the same energy
value as wood. Consumers began to realise that the fuel was burning more quickly
than they thought it would, with less heat output than they had been led to
believe, and they stopped buying it.
I imagine that the situation of very cheap firewood
is replicated in many other developing countries due to the absence of formal
controls on harvesting and transport and the low cost of labour. Since I came to
Kenya in 1990 the price of firewood has 'only' doubled, whereas the value of the
local currency has diminished by a factor of 10. Its local purchase price simply
doesn't reflect any dependable economic indicators, and it is a fuel against
which no-one can compete without a drastic change in the way its sourcing is
controlled.
Hence our decision (with Elsen Karstad
at Chardust Ltd.) to get into charcoal fuels. We CAN compete against
charcoal as it is an urban middle class fuel for which people are willing to pay
above the odds for convenience and quality. It is transported as far as 250 km
into Nairobi and the retail price is normally around $90 per tonne. This gives
the formal sector some chance to compete. Note that we cannot afford to extrude
the sawdust and then carbonise the briquettes due to the incredibly high
pressures and temperatures that this requires. We have decided to carbonise the
sawdust first and then briquette it afterwards at low temperatures and pressures
to keep costs of machinery and electricity down - for which we must accept a
higher ash content (but longer and more even burn).
Jim Dunham mentions that he has successfully set up
units all over the world to briquette raw biomass such as sawdust. Certainly I
suspect that what I've said about raw sawdust briquettes doesn't apply in many
developed countries, where firewood prices are much higher and a greater value
is placed on proper use of residues. There may indeed be an opportunity to
compete in such circumstances.
Then again we don't have to contend with any
emissions regulations either during manufacture or final combustion, which
although we aim to flare all volatiles and produce low emissions fuels, does
allow us a certain experimental leeway out at the production facility that Jon
Flottvik in British Columbia would die for!
Matthew Owen
Chardust
Nairobi
Date: Thu, 11 Jan 2001 07:35:06
+1000
To: "John Flottvik" <jovick@island.net>
From: Peter
Verhaart <verhaarp@janus.cqu.edu.au>
Subject:
Re: Charcoal
Conversely, why, instead of going through all that
trouble to turn sawdust into charcoal briquettes, why not make it into
sawdust briquettes.
Having briquettes means having fuel in standard
shape, size and mass.
Look what people have done with lumps of fuel of
standard size and mass. There is the Pyromid stove and the much maligned
Weber Kettle BBQ.
But they work, they do exactly what the manual
tells you they do. Why? Because someone has painstakingly done test after
test to arrive at numbers, patterns and times to ensure the desired
behaviour (don't hit him, it's English).
The same thing can be done for
wood. If you detest the downdraft mode, then you could follow the Pyromid
strategy. With wood briquettes laid out in a certain pattern and with
provisions for a supply of air at the right spots, I am sure a burner
with many small smokeless flames can be realised.
And it uses all of the
combustion value of the wood.
Happy New Year and a happy new
Millennium to all stovers.
Piet Verhaart
At 07:47
9/01/2001 -0500, you wrote:
January 9,
2001
Dear
Stoves
Hope every one had a
good holiday
This is probably
a stupid question, but, if you are going so far as to make torrified wood,
why not go the one extra
step and make
charcoal? By going the exta mile, you are able to collect all the oil from
the wood, and sell, at a good price, I might add.
Regards John
Flottvik
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