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"The 4,000 plus fixed chimney kilns form the largest stationary source of GHG emissions in Bangladesh which is around 5.4 million tonnes of CO2 annually. Besides the air pollution, brick making industries contributes to three other serious environmental concerns: land degradation, deforestation and depletion of water resources”
International Labour Office (Geneva) Report
Skills for Green Jobs in Bangladesh – 2010
THE BRICK INDUSTRY
- Brick making industry is described as the single largest emitter of industrial black carbon in Asia – major contributor to Atmospheric Brown Cloud (ABC).
- Significant impact on global warming.
- Large emitter of CO2 and green house gases (GHG) due to the high use of coal and scavenged fuels – emitting 890 million tonnes CO2 p.a.
- At a conservative estimate, 300,000 outdated brick kilns burn 1,500 billion bricks p.a., consuming 375 million tonnes of coal – plus scavenged fuels
- Significant social problems – clean air, health, safety, living and working conditions, in addition to regional problems.
THE BRICK MARKET
The brick making industry in developing countries is most often the industry of the very poor and under-privileged.
The use of primitive and highly polluting clamp kilns is widespread in India and Africa, Fixed Chimney Bulls Trench Kilns (FCBTK) are predominant in Bangladesh and Nepal, where pressure for low emission technology is mounting due to high pollution levels and health concerns.
WORLD BRICK PRODUCTION
||No. Billion P.A.
|Rest of Asia
|Rest of World
|Total Rest of World
|Total World Production
Source: Ellen Baum - Session 1, Mexico & India: GKSPL Estiate, Pakistan: Estimate based on CIWCE report Lahore, Bangladesh & China: ESMAP & World Bank Report, Vietnam: Ministry of Construction Vietnam
Bricks made in developing countries are predominantly hand-made; bricks in the developed world are machine made in highly automated tunnel kilns.
The basic concept of brick kiln technology in developing countries has
changed little over the past thousands of years. Brick making is an ancient
technology. Bricks are made, dried, fired and cooled.
Kilns first started in pits, walls were then added. The addition of a chimney
stack, improved the air flow or draw of the kiln, thus burning the fuel
more completely. Several variations have been invented over the years
with varying degrees of efficiency and cost.
Brick kilns fall into one, or both, of the following categories:
Kilns are sealed and the internal temperature increased according
to a schedule. After the firing process is complete, both the kiln
and bricks are cooled. The kiln is left to cool sufficiently before the
bricks can be removed.
Due to the relative ease and cost of construction these are the
kilns types primarily used in developing countries.
Continuous (or Tunnel)
There are two types of continuous kilns:
- Tunnel kiln – the bricks are moved through a stationary
fire zone, like a train in a tunnel.
- Continuous kiln – the bricks remain stationary and the
fire moves through the kiln with assistance or help of a
chimney or by a suction fan (Habla Zig-Zag Kiln, Hoffman, FCBTK, Metal Chimney Bull Trench)
The main difference is that the tunnel kiln is vastly more expensive
to build however it saves on labour costs and can be highly
automated, bricks can be made and burnt without being touched
by human hands. The kiln requires highly skilled labour and a guaranteed electricity supply.
The following kilns are most commonly in use today:
Clamp Kiln – ANCIENT TECHNOLOGY 4,000 B.C.
Amongst the most commonly used kiln in the developing world. These kilns have
a devastating impact both on the environment and workers. Generally
built with four brick walls like a room, then green bricks are stacked
inside. They are inefficient in fuel, labour intensive and highly polluting.
They are only operated in intermittent mode. To produce higher brick
production clamp kilns are frequently built, grouped and operated in
Hoffman Kiln – INVENTED GERMANY 1858
These kilns have a large permanent arched masonry and an expensive tall masonry chimney of about 30 metres. They must operate in continuous mode.
Tunnel Kiln – INVENTED GERMANY 1877
Most common in developed countries, since their invention tunnel kilns
have now become highly automated and are for large brick production.
Bricks move mechanically through a long stationary fire zone. They have
minimal labour requirements but a very high capital cost. They must be
operated in continuous mode and require a guaranteed electricity supply.
Bull's Trench Kiln – INVENTED ENGLAND 1876
- Metal Chimney Movable Bull's Trench Kiln was commonly used in India and many developing countries. It is now generally banned due to high pollution levels. The kiln uses movable metal chimneys which are lifted and man-handled by a team of workers into different positions as the fire moves through the kiln. Has very high emissions, dispersed over a wide area, working conditions are hazardous.
- The FCBTK is an improved version of the Bull's Trench kiln with a permanent, fixed brick chimney approximately 30 metres high. Emissions are high. The chimney requires skilled bricklayers to construct and is costly to build. The kiln can only be operated in continuous mode. It has no roof and cannot be used during the monsoon season.
Vertical Shaft Brick Kiln (VSBK) – INTRODUCED FROM
Reasonably fuel efficient however the kiln is limited due to a low
throughput. Green bricks are loaded into the shaft and therefore must be
hauled up a ramp to the top of the kiln. Highly clay specific.
Habla Zig-Zag Kiln – INVENTED GERMANY 1927
The Habla Zig-Zag Kiln is the most fuel efficient kiln yet invented and the cheapest to build. It features a long fire zone advanced by a suction fan. The Habla Zig-Zag Kiln consumes less fuel, uses less mechanical energy and requires far less capital outlay with almost no maintenance. It also has a roof resulting in improved working conditions, the potential of water being collected and longer operational time during monsoon conditions. Solar energy can be used to power the fan. The Habla Zig-Zag Kiln is ideally suited to both large scale continuous brick making operations and to small semi-continuous village applications in developing countries.
Brick making consists of the following processes:
- Winning – digging for clay
- Preparation – preparing the clay for shaping
- Shaping – moulded using various mould types and
methods, by hand or by machine
- Drying – open air, hot floor, chamber, tunnel, etc
- Firing – various kiln methods including Bull’s Trench,
Clamp, Habla, Hoffman, Tunnel, etc.
- Quality Control – sorted into grades, e.g. firsts, seconds,
- Dispatch – sales