Slavery in brick manufacture

Clay Technology magazine
17 May 2018

Khai Trung Le looks at the use of satellite imagery to track slavery in brick manufacturing.

The number of kilns along the South Asian Brick Belt, an unofficial stretch of brick manufacturing across parts of Pakistan, India, Bangladesh, and Nepal, and known site for modern day slavery, has been estimated using Google Earth technology, helping to calculate the scale and impact of slavery. 

The most recent estimate from the Global Slavery Index indicates that more than 40 million people are enslaved. However, there is a global political commitment to ending slavery, including through the United Nation’s Sustainable Development Goal target 8.7, which aims to eliminate all forms of slavery by 2025.

The Rights Lab, a University of Nottingham, UK, research platform aims to achieve this. It asserts that, at the time of writing, there are 55,387 brick kilns along the Belt. Although there have previously been regional estimates, the full scale was unknown, making action from appropriate organisations near impossible. Brick kilns have long been linked with exploitation of workers, with the Rights Lab stating many have been trafficked into bonded labour slavery.

Dr Doreen Boyd, lead researcher of the study, told Clay Technology, ‘Accurate information on slavery activity is not easy to come by and is one of the biggest barriers in the fight against slavery. Building on previous work [the Rights Lab] has carried out, we wanted to find a way of calculating the number of brick kilns on the Brick Belt, which is an area notorious for using slaves, so that we can help to provide a clear picture of the true scale of the problem.’

Fighting injustice 

Although many different types of kilns are used along the Belt, the most common is known as the Bull’s Trench kiln, a large oval kiln so distinct in shape as to be visible in satellite imagery. The Belt stretches across 1,551,997km2, so the Rights Lab team took a probability sample of 100km2 from satellite imagery purchased by Amnesty International, and identified the kilns within. This was corroborated by ground intelligence from non-government organisations confirming the breadth of brick manufacturing in the area. The average density was then scaled up over the region to make an estimate of total kilns. 

Boyd continued, ‘We cannot successfully fight this abhorrent industry if agencies don’t know what resources they need to do so. This calculation is just the first step in helping agencies worldwide in preparing action plans on how to tackle the problem. There is a long way to go. Meanwhile, we hope that this initial work is a small step towards achieving freedom across the globe for everyone.’ See Clay Technology February 2018 for more on using satellite imagery to fight damaging brick production in Bangladesh.

To read Slavery from Space: Demonstrating the role for satellite remote sensing to inform evidence-based action related to UN SDG number 8, published in the ISPRS Journal of Photogrammetry and Remote Sensing, visit