Zigzag 2.0: Can this breakthrough make Bangladesh’s brick kilns green?

About a thousand brick kilns in greater Dhaka operate from October to March, emitting approximately 1.8 million tonnes of carbon dioxide, according to a study published in the journal Cleaner Environmental Systems.

If we do the math — the volume of one tonne of carbon dioxide at STP (standard temperature and pressure, used as a reference point in gas measurements) is approximately 556.2 cubic metres — then 1.8 million tonnes of carbon dioxide could fill over 400,000 Olympic-sized swimming pools. 

But if this alone were not enough, the thousand brick fields of greater Dhaka also emit 302,200 tonnes of carbon monoxide, 23,300 tonnes of particulate matter, 15,500 tonnes of sulfur dioxide, and 6,000 tonnes of black carbon to produce 3.5 billion bricks annually.

Bangladesh has over 7,000 brick kilns across the country — a major source of greenhouse gas emissions and air pollution, which pose a significant public health burden.

Despite efforts spanning several decades, attempts to curb emissions from this industry have seen limited success. Though Bangladesh converted around 80% of its brick kilns to the zigzag system, most of these kilns were not operated properly.

However, a group of researchers led by Nina Brooks of Boston University, who published their findings in Science journal, has developed a low-cost intervention, which they call Zigzag 2.0, to improve the energy efficiency of zigzag kilns by conducting a randomised controlled trial across approximately 276 kilns in Bangladesh.

"Kiln owners who adopted Zigzag 2.0 were extremely happy with the changes, which supports the long-term sustainability of the intervention," Brooks, an assistant professor of global health and core faculty at Boston University's Global Development Policy Center, told The Business Standard. 

Moogdho Mahzab, a co-author of the study, associate research fellow at the International Food Policy Research Institute (IFPRI) and acting country representative for IFPRI-Bangladesh, said the country was once dominated by fixed-chimney brick kilns, which have since been banned. 

In their place, the zigzag method was introduced. While zigzag kilns are an improvement in many respects, they are still not being operated to their full potential. 

"Our Zigzag 2.0 introduces a new brick-stacking pattern, single-fireman coal feeding, and several other small changes that are expected to increase combustion efficiency. The team is also working on Zigzag 3.0 with further modifications. For example, I worked with Stanford mechanical-engineering students to develop an automatic coal feeder that will eliminate manual feeding and improve coal-feeding efficiency. Other upgrades are under way for Zigzag 3.0," Moogdho told TBS. 

Under the intervention plan, the kilns' staff received information, training and technical support to adopt operational improvements that enhance fuel combustion and reduce heat loss.

In addition, the kilns received "incentive information" explaining the business rationale for encouraging workers to follow the new practices. 

"Our study demonstrates that meaningful reductions in emissions by traditional kilns are achievable, even in the absence of stronger regulations, if they can be made financially attractive to private kiln owners," the Science article summary mentions.  

The interventions in these kilns led to a 20% reduction in carbon dioxide and particulate matter emissions, as well as a 23% decrease in the energy required to fire bricks. 

The kiln owners also benefited, with fuel costs per brick falling and the quality of bricks improving.

"The key to the high adoption of the Zigzag 2.0 package was that these practices delivered tangible economic benefits to kiln owners — they saw an 18% increase in Class 1 brick production and saved over $35,000 on fuel costs," Nina Brooks said. 

"The key to the high adoption of the Zigzag 2.0 package was that these practices delivered tangible economic benefits to kiln owners — they saw an 18% increase in Class 1 brick production and saved over $35,000 on fuel costs."

Nina Brooks, assistant professor of global health and core faculty, Global Development Policy Center, Boston University

What makes the Zigzag 2.0 package particularly attractive is that it required no capital investment from kiln owners. The only expense was the technical training and support provided by Brooks' team throughout the season. 

These costs, covered by their research funds, amounted to $486 per kiln — an amount that compares very favourably with the fuel savings realised by the owners.

To estimate the cost-effectiveness of Zigzag 2.0, the researchers calculated the value of CO2 emissions reduced per kiln using a social cost of carbon of $185 per tonne and compared this to the cost of implementing the programme. 

Because the societal benefits of cutting CO2 are substantial, and the costs of delivering Zigzag 2.0 were relatively low, the cost-benefit ratio shows that the benefits outweigh the costs by 65 to 1. 

"We believe it is important to emphasise that these benefits are likely significantly underestimated. Firstly, because the social cost of carbon does not factor in the health benefits of reduced particulate matter, and secondly, because the training costs are a one-time expense, kiln owners continued to follow Zigzag 2.0 practices in the following season," Brooks explained.

The team said they built upon a low-carbon solution developed by Delhi-based Greentech Knowledge Solutions, identifying modifications to typical zigzag kiln operations that could improve energy efficiency. They also observed that kilns adopting these practices experienced economic gains. 

"Our team spent several years adapting and piloting this technical package [Zigzag 2.0] in Bangladesh before rigorously evaluating it through this randomised controlled trial," Brooks said.

When zigzag kilns were first mandated by the government, kiln owners were not given any guidelines or standards to assist with the conversion from fixed chimney kilns.

Kiln owners were unaware of how to operate their zigzag kilns correctly, and none had received any formal training. They greatly valued having access to the project engineers throughout the study to help troubleshoot Zigzag 2.0 and resolve other operational issues. 

"Our team has already been working on scaling Zigzag 2.0 in Bangladesh, at the request of the Bangladesh Department of Environment, focusing on Khulna and Dhaka. We are exploring strategies to accelerate the adoption of Zigzag 2.0 by harnessing kiln owners' ability to learn from one another, thereby extending the intervention's reach. To date, we have helped over 500 zigzag kilns adopt the Zigzag 2.0 package, and our ambition is to reach all zigzag kilns — around 7,500 — across the country," Brooks said.

The success of the Zigzag 2.0 intervention depended heavily on the workers' willingness and ability to adopt the new practices. 

"While this experimental arm was primarily designed to tackle labour-related barriers to adoption, we also hoped that the information and encouragement would lead to improvements in conditions for workers, who face harsh circumstances and are often severely exploited," she said.

The researchers are hopeful that evidence from Bangladesh will serve as an example for others to adopt similar changes to reduce emissions.

Brooks said that aligning profit motives with environmental and health improvements offers a promising path for certain industries in countries with weak regulatory frameworks. 

Moogdho said that if properly implemented, Zigzag 2.0 is expected to significantly reduce carbon and particulate-matter emissions. 

"Given how Bangladesh is exposed to various kinds of environmental pollution, this could be a life-saver for us. When I was in the field and now living in Dhaka, I know how the brick-kiln season can be devastating because of the pollution it emits. Our method is a win-win for everyone. If we can scale it up across the whole country, it will definitely save many lives in the future," Moogdho added.