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Dear Matthew,
you are right about the high cost and low calorific
value of briquettes made out of compacted sawdust and other biomass.
Charring it is simple and briquetting the char is also quite simple. Both
can be done at a very low capital cost by a third world farmer. We have
modified an old fashioned meat mincer into an extruder. We first operated
the extruder manually, and after being satisfied with its performance, we
are now fitting it with an electric motor, to increase its output. But the
extruder is not obligatory, as one can just manually shape the charred
biomass (after mixing it with a binder), into balls having a diameter of about 5
to 6 cm, and dry them in the sun. These balls can serve as fuel not only
in a conventional charcoal burning stove but even in a pyromid stove.
There is no real shortage of firewood in the
rural areas of our state (Maharashtra, India), because of the availability of
combustible agrowaste in the form of stalks of cotton and pegionpea, as well as
abundant availability of Prosopis juliflora (mesquite) trees. The farmers have a
lot of light biomass which is today not used as fuel (e.g. dried sugarcane
leaves, wheat straw, stover of safflower, sunflower, sesame, mustard etc.), and
often just burnt in situ, just to get rid of it. The farmers are not
interested in making charcoal briquettes out of this biomass for their own use,
but if somebody arranges to collect the charred biomass from the farmers,
and produces them into briquettes, there is a good market for the latter in
the cities. We have formed a cooperative, which would do just
this. We do not see any difficulty in selling the char briquettes in the
cities, because there exists a ban of the production of wood charcoal (as a
measure of saving the trees). As a result of the ban, the charcoal prices have
shot up to US$ 150 per tonne.
Yours A.D.Karve
Sent: Tuesday, January 16, 2001 11:13
AM
Subject: Re: Re: Charcoal
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
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