Sustainable small-scale brick production
Practical Action
clamps are 2.04 MJ of energy, 0.233 kg of CO2 and 0.04 kg of SO2 per kg of fired brick,
which again are low. Firing with boiler waste reduces the energy use to 1.56 MJ/kg whilst
releasing 0.251 kg CO2/kg of brick. Without data about soil types and brick quality, these
figures are no more than indicative of energy efficiency. In fact, some of the larger kilns in
Zimbabwe do use more energy per kg of fired brick but their end product is also better. Using
coal instead of wood only has marginal direct environmental benefits but leaves the trees as a
CO2 sink. Using boiler waste has the additional advantage of getting rid of a residue, the
disposal of which can cause environmental problems.
Practical Action's intervention in Peru is more recent. Initial studies revealed differences in
brickmaking technologies according to the three distinct regions of Peru: a desert coast, bare
highlands, and the forest. The predominant firing technology is the Scotch kiln. The coast and
the Andean regions face severe fuelwood shortages, whilst this fuel is used, albeit inefficiently,
in the forest region. Practical Action started by applying some of the lessons learnt in
Zimbabwe, that is, to adapt Scotch kilns to coal firing. This was not entirely new to Peru, in a
few locations some coal was already used together with wood. Contrary to Zimbabwe, the coal
used in Peru is third grade, largely because that is the only alternative affordable to
brickmakers. Its quality is quite variable, which can cause problems, and will require the
development of a simple quality test.
The initial research, around Piura, replaced only half of the wood by coal which was spread
through the kiln, whilst wood was fired in tunnels underneath. This improved energy efficiency
and reduced costs by 7% to 15%. The next step was to attempt full substitution by coal, using
hand moulded balls of coal dust and clay in the tunnels, which reduced energy costs by half.
Overall, energy consumption has come down from around 3.8 MJ/kg of fired clay in the
traditional kiln to an average 2.1 MJ/kg when firing mainly with coal. Still, wood was used to
ignite the kiln. Further research has revealed that this could be substituted by the use, for a
couple of hours, of oil burners. In Ayacucho, some brickmakers already had a habit of using
12% to 20% by weight of coal, with the remainder being eucalyptus wood, with a typical
energy consumption of 2.5 MJ/kg, Initial research here, reversed the fuel type proportions, and
energy use halved but this resulted in some underfiring and needed to be adjusted upwards.
Fieldwork in Peru is now researching the use of other residues as fuel. Around Piura, rice
husks are already used but their high ash content obstructs air flow in the kiln, leading to
lower quality bricks. That problem will have to be addressed. Practical Action is currently
learning the lessons from the traditional use of rice husk as a fuel and adapting kilns to use it
more effectively. Other residues with potential to be used as a fuel in Peru including cotton
stalks and sawdust have now been used to replace firewood completely. Sawdust is
incorporated into the brick mass during production by brick makers in Piura and ignited using
a burner fired by recycled oil.
In Sudan, the brick industry consumes over half of the fuelwood nationwide. In the East,
where Practical Action works around Kassala, good wood has to be brought from the Blue Nile
region, far to the South. The only available local wood is mesquite, which is less than 10 cm
thick and therefore not a very satisfactory fuel. In Sudan, bricks are usually made by slop
moulding, which is fast, but produces a poor quality brick. Some cowdung is mixed in the
clay; this is made possible because cowdung is not used as a fertilizer at the moment. Bricks
are fired in large clamps, usually containing more than 100 000 bricks.
Practical Action's intervention, dating from 1995, has so far focused mainly on improved
moulding and the question of fuel. Slop moulding was replaced by the much drier sand
moulding, using a slightly larger mould to produce standard size bricks. 'The resulting bricks
are better, much in demand and fetch a price 10 to 20% higher than traditional bricks. Sand
moulding is, however, slower and since brick moulders are paid piecemeal, it is important that
some of the extra income benefits them. In the 1999 season the Shambob Brickmakers Co-
operative, supported by Practical Action, sold more than 1 million of these improved bricks
and faced demand for many more.
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