The major disadvantage of the portable steel kiln over traditional kilns is its increased cost: even with
local manufacture, this is about $1000 and, in many places, considerably more. Given a working life
of 2-3 years, it can be very difficult to justify economically in areas where labour costs and charcoal
prices are low.
Charcoal from mesquite shrubs in Sudan
Practical Action has made use of portable steel kilns in Sudan to make charcoal from Mesquite
(Prospois) which is a perennial woody plant that can grow in the arid conditions of Sudan. It was
promoted in the 1970s and 1980s and a source of fuel wood, pods for fodder and as a way of
stabilising soil in efforts to combat desertification. However, it has caused problems when
unmanaged as it spreads into area of grazing and farming land and has become very difficult to
control. The situation has resulted in the plant being declared a noxious weed in Sudan and there
is a program of eradication. charcoal production using mesquite is part of this eradication program
that can also provide an opportunity for some to improve their income.
The project uses mobile metal kilns based on the design for carbonization of cotton stalk as part of
the Biomass Technology Group at the Energy Research Institute in the 1980s which is similar in
design to a MARK V metal kiln (a well known charcoal kiln) but of smaller volume and weight to
allow for easy transportation, with a volume of about 2m³. Its nominal carbonization efficiency is
around 25%. The metal kilns additional advantage over the normally used earth-mound kiln is that
it enables fine charcoal to be made from the small branches of the Mesquite shrub.
The metal kiln can be fabricated locally at a low cost as it can be made from empty oil barrels
which are purchased in Kassala market.
The mini-charcoal kilns in used in many locations. One design of mini Charcoal kilns is described by
E G K Rao, India in the Magazine Boiling Point No 6, April 1984. This describes a kiln that is
constructed from an oil drum based on a traditional design form the Philippines used to process
coconut shell. It yields over 30% high grade charcoal from an 80 kg charge of firewood.
One person could operate a batch of about 10 oil barrel kilos, producing up to 250 kg of high quality
charcoal per day. The major drawback of this type of kiln will be its short lifetime, but where there
are cheap oil barrels and a good market for high quality charcoal, it could be a profitable small
Briquettes made of agricultural waste can compete with traditional woodfuel if they are of sufficient
quality and are priced correctly. This allows the conversion of low-grade residues to marketable fuels.
The work by MIT D-Lab in producing charcoal briquettes is described in the technical brief Fuel from
the Fields: Charcoal from Agricultural Waste.