Needles in a haystack
Brick production is central to construction in Bangladesh, which lacks domestic sources of many other construction materials (1,2). In Bangladesh, and across South Asia, bricks are produced in traditional kilns where hand-molded clay bricks are fired with coal. The industry is is dominated by traditional, fixed chimney kilns that are located on the low-lying floodplains and operate only in the dry, winter months (1,2). Burning coal to produce bricks emits a number of pollutants into the atmosphere, including CO2, SO2, CO, NOX, suspended particulate matter and black carbon. Consequently, brick production contributes to global climate change (3-5), as well as exacerbates local air quality (6), adversely affecting human health. Recent estimates suggest that the loss in life expectancy attributable to air pollution in Bangladesh, an average of 1.87 years per person, is higher than any country in the world (7). Brick manufacturing also affects agricultural yield, as brick kilns utilize fertile soil from nearby farmers as a key input to brick making (8), and air pollution that deposits on farmland directly inhibits plant growth (9).
Because of the many adverse consequences of brick manufacturing, the Government of Bangladesh (GoB) has enacted numerous regulations to restrict where brick kilns can be established and mandate cleaner manufacturing processes (1,10). Unfortunately, these regulations are rarely enforced. For example, where brick kilns with shorter chimneys were banned in 2002, the Department of Environment stopped reporting these in official statistics, yet many remained in operation throughout the country (1). In fact, while the GoB reports there are approximately 6,000 brick kilns in Bangladesh (10), there is no accurate accounting of how many traditional kilns are operating because many are either not counted because they violate various regulations or are never registered to begin with.
We are collaborating with the Stanford SustainLab to take advantage of advances in machine learning and improvements in satellite imagery to develop a convolutional neural network (CNN) to locates all of the traditional brick kilns in Bangladesh. Undergraduate computer science student Jihyeon Lee has led the efforts to develop the model and generate a reproducible pipeline. We use satellite imagery from DigitalGlobe with images of 224x224 pixels at 1m spatial resolution . We begin by compiling a training dataset of satellite images containing those coordinates with class labels of positive (contains kiln) or negative (does not contain kiln) and trained a model for classification, using a transfer learning approach. Then, we implemented a weakly supervised approach for localization that identifies where within an image a kiln is located and then extrapolate a more precise geographic location. Finally, we added an additional dense node at the very end of the CNN to classify whether each identified kiln is a traditional fixed-chimney kiln or a zigzag kiln.
We will use this data to catalyze a discussion among brick kiln owners, government regulators, researchers and civil society. The objective is to motivate progress toward a manufacturing system that generates less environmental and health harm.
- Stephen P. Luby, Debashish Biswas, Emily S. Gurley, and Ijaz Hossain. Why highly polluting methods are used to manufacture bricks in Bangladesh. Energy for Sustainable Development, 28:68–74, October 2015.
- The World Bank. Introducing Energy-efficient Clean Technologies in the Brick Sector of Bangladesh. Technical report, IBRD/World Bank, Washington, DC, 2011.
- Bilkis A. Begum. Investigation of sources of atmospheric aerosol at urban and semi-urban areas in Bangladesh. Atmospheric Environment, 38(19):3025–3038, June 2004.
- Bilkis A. Begum, Philip K. Hopke, and Andreas Markwitz. Air pollution by fine particulate matter in Bangladesh.Atmosphere Pollution Research, 4, 2013.
- Cheryl Weyant, Vasudev Athalye, Santhosh Ragavan, Uma Rajarathnam, Dheeraj Lalchandani, Sameer Maithel, Ellen Baum, and Tami C. Bond. Emissions from SouthAsian Brick Production. Environmental Science & Technology, 48(11):6477–6483, June 2014.
- Sarath K. Guttikunda, Bilkis A. Begum, and Zia Wadud. Particulate pollution from brick kiln clusters in the Greater Dhaka region, Bangladesh.Air Quality, Atmosphere & Health, 6(2):357–365, June 2013.
- Joshua S. Apte, Michael Brauer, Aaron J. Cohen, Majid Ezzati, and C. Arden Pope.Ambient PM2.5 Reduces Global and Regional Life Expectancy. Environmental Science & Technology Letters, 5(9):546–551, September 2018.
- Debashish Biswas, Emily S. Gurley, Shannon Rutherford, and S. P. Luby. The drivers and impacts of selling topsoil for brick making in Bangladesh. Environmental Management, 62(4):792–802, 2018.
- A. D. Bhanarkar, D. G. Gajghate, and M. Z. Hasan. Assessment of air pollution from small scale industry. Environmental monitoring and assessment, 80(2):125–133, 2002.
- Department of Environment. National Strategy for Sustainable Brick Production inBangladesh. Technical report, Dhaka, Bangladesh, May 2017.