In the dry winter of Bangladesh, thousands of workers shovel millions of tons of coal into kilns across the country. When the hand-piled brick columns were baked and hardened in the kilns, black smoke from more than 8,000 chimneys shrouded the urban and rural skylines. “A large amount of black smoke not only affects workers and nearby villagers, but also threatens the air quality of the entire area,” noted Sameer Maithel, an engineer at Greentech Knowledge Solutions, a consulting firm in Delhi, India.
As one of the countries with the poorest air quality in the world, 10% to 40% of the air pollutants in Bangladesh come from the tiny particles emitted by brick kilns. These particles can penetrate deep into the lungs and even the bloodstream, causing health problems such as respiratory diseases, strokes and even cognitive impairments. However, a new study published in the journal Science by Mercer and her team, covering 275 kilns, suggests that a simple change in the way bricks are stacked could significantly reduce pollution. William Checkley, an epidemiologist at Johns Hopkins University, commented: “This fully demonstrates that low-cost intervention measures can have a significant impact on energy utilization.” If it can be promoted, it will significantly improve energy efficiency and air quality in Southeast Asia.
The pollution predicament and technical bottlenecks of traditional brick kilns
Bricks are the core pillar of infrastructure construction in Bangladesh. This densely populated and rapidly urbanizing country produces nearly 30 million bricks every year, over 90% of which come from loosely regulated coal-fired kilns. “Traditional brick kilns are easy to build and have low costs, and thus have spread rapidly,” explained Nina Brooks, a global health researcher at Boston University. The production process is usually as follows: First, the yellowish-brown clay bricks are pressed with wooden molds. After being dried in the sun, hundreds of thousands of bricks are piled into the combustion chamber and covered with ashes. Workers continuously shovel coal for firing. Brooks pointed out: “The combustion efficiency of these brick kilns is extremely low, resulting in coal consumption far exceeding the actual demand. This is precisely the root cause of their severe pollution.”
Each kiln can employ up to 200 workers, who are the direct victims of smoke – a study shows that nearly 80% of the workers report respiratory discomfort. Furthermore, kilns are often located close to densely populated areas, exacerbating the smog caused by urban life. Despite the existence of regulations on the site selection of kilns, the phenomenon of poor enforcement is widespread. “We found that 77% of the brick kilns were illegally built near schools,” Brooks disclosed.
The pollution emissions of modern high-tech kilns have been significantly reduced, but their construction and operation costs are as high as 25 times that of traditional kilns, making them difficult to be popularized. The research team turned to seek low-cost solutions that were more easily adopted by small and medium-sized brick factories.
Disruptive innovation: The dual practice of airflow optimization and continuous energy supply
As a consulting engineer who has collaborated with brick kiln owners in India for decades, Mather has long noticed the unreasonable aspects in traditional operations: many kiln workers stack the bricks too densely, which hinders the circulation of oxygen and prevents the hot coal from sinking, resulting in uneven doneness of the bricks; Meanwhile, workers are accustomed to taking collective rest after scoveling coal in groups, which leads to unstable fuel supply and further reduces efficiency.
Based on the principles of energy system engineering, Mather proposed two key improvements: adopting the zigzag brick stacking method to increase air circulation, and ensuring the continuous and uniform feeding of coal. The more thoroughly the fuel is mixed with the air, the lower the possibility of generating black smoke. To verify the effect, the research team conducted a large-scale experiment in 276 kilns: one group received operation training, another group was further informed of the expected cost savings, and the control group remained the same. During the winter firing period, researchers monitored key indicators such as fuel consumption.
The results are encouraging: The fuel consumption of kilns adopting the new method has decreased by an average of 23%, and carbon dioxide and particulate matter emissions are expected to be reduced by approximately 20%. Mahbubur Rahman, an environmental health researcher at the International Centre for Diarrheal Diseases Research in Bangladesh, said: “We have proved that simple and low-cost intervention measures can indeed reduce pollution.” The reduction in fuel costs has enabled kiln owners to save nearly $40,000 per season, and the quality of bricks has also improved simultaneously. It is worth noting that one year later, the kiln owners who participated in the experiment are still continuing the new operation, demonstrating the continuous appeal brought by the actual benefits.
At present, a research team composed of scientists from the United States, India and Bangladesh is collaborating with the government of Bangladesh to promote the expansion of the training program. “This is a promising case that proves the solution is feasible,” Brooks concluded. As more kilns join the ranks of innovation, this micro-innovation derived from the brick-stacking method may become an important key to solving the air pollution predicament in Bangladesh.
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