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< prev - next > Construction Clay bricks KnO 100102_Sustainable small scale brick production (Printable PDF)
Sustainable small-scale brick production
Practical Action
The research into fuels has different strands. A downdraught vaulted kiln, of 20 000 bricks
capacity, was built and equipped with oil burners. The initial indications are that this could
make substantial savings on fuel costs, but the kiln is still not yet functioning optimally, and
will require some further work to obtain reliable data.
Practical Action is also studying the various parameters involved in the use of cowdung, so as
to optimise it. In Sudan, cowdung is considered a good additive, because it increases
plasticity, reduces breakage and being an internal fuel, seems to increase efficiency, adding
too much, however, reduces strength and increases porosity. The optimum range seems to be
between 20% and 30%. Using sand moulding and increasing the proportion of cowdung
enabled Practical Action to reduce the energy share of production costs from 53% to 36%,
whilst saving 44% on wood. At the same time, the share of labour costs increased from 42%
to 59%, allowing higher payments for sand moulding.
Further experimental firings used bagasse as fuel. This residue is widely available from sugar
factories in Sudan. If can be used as a mixture in the clay or burnt as briquettes. The latter
are made from bagasse and molasses as a binder. The briquettes are formed in a soil block
press. One test clamp of 55 000 bricks used 0.114 kg bagasse per brick (instead of
cowdung), which comes to 12.4% of overall costs, and 6827 kg wood, fired in the tunnels,
representing 15%; the overall energy use amounted to 2.3 MJ/kg of fired brick. Another
clamp; of 63000 bricks, used the same amount of bagasse in the bricks, in this case
amounting to 11.5% of overall costs, and a mixture of 1439 kg of wood and 3325 kg of
bagasse blocks in the tunnels, these costs being 20%. The overall energy use here was 176
MJ/kg of brick, which is perhaps a sign of underfiring. Thus, the energy share of production
costs was further reduced. Unfortunately, in this case transport represented a substantial part
of the costs of bagasse based fuels and greater savings can be expected in locations closer to
sugar factories. Practical Action has: however, firmly established that it is possible to replace
at least half the fuelwood by bagasse blocks. Initial tests to replace three quarters of the wood
are promising.
Finally, Practical Action started working with brickmakers in Sri Lanka in 1998. Preliminary
studies indicated that there are more than 5000 brick-works in the country, producing over
500 million bricks per year; 85% of which by SMEs. There is widespread use of both clamps
and Scotch kilns, two-thirds of which are in the 10000-25000 brick range. The brick and tile
industry in Sri Lanka consumes in excess of 150 000 tonnes of fuelwood per year, half of
which is rubberwood. Some producers have reverted to using offcuts from sawmills and a few
use rice husk. The principal objective of Practical Action's project is to investigate to what
extent residues such as sawdust, coir dust and rice husk can be used as fuelwood substitutes,
which links it closely to the work in Peru and other international research.
Work has started with three pilot producers in the Kandy region. This has involved the
incorporation of sawdust, at about 20% by volume, in brick clays; this has improved the drying
process and reduced cracks. Thus, the number of broken bricks has reduced greatly to less
than a tenth of the original 3% to 4%. In addition, saw dust with some firewood was placed in
channels incorporated higher up in the kiln, a tradition also known in Ecuador. So this limited
experience has led to a reduction in firewood use by 21% and to an equivalent saving in the
cost of fuel; the reduced wastage led to further savings.
The brickmakers Practical Action works with have few marketing problems; markets for bricks
are generally expanding and improved quality bricks in particular satisfy the increasing
demand from urban markets. Their viability and sustainability, however, is threatened by a
fuelwood crisis affecting the environment and the people in many locations. One key strategy
therefore is to increase the fuel efficiency of SMEs.
Over the years, it has become clear that for small brick producers their immediate livelihoods
are of greater concern than the long-term sustainability of their production. For them, cost