Characterizing aerosol emissions from traditional clay fired clamp kilns in South Asia

Fired clay brick kiln (FCBK) industry is one of the unorganized and often overlooked sectors in terms of its regional air quality and health impacts. Approximately 87% of the 1.5 trillion clay bricks produced worldwide annually are made in Asia. These bricks are typically fired in small-scale traditional kilns that burn coal or biomass without air pollution controls. Clamp kiln is the most traditional technology of brick manufacturing. It is a batch-style kiln that produces 10,000-200,000 bricks per batch in a time period of two to four weeks. It uses coal as primary and firewood and rice husk as supplementary fuel. There is no chimney, and hence the smoke escapes from the cracks at the top and from the sides of the kiln. Very little information is available on aerosols emitted from these kilns. Therefore, it’s important to accurately estimate aerosol emissions and their chemical properties from FCBK to understand their impact on regional air quality and climate. This study examines the chemical and optical properties of emitted aerosols during different stages of combustion in clamp kilns. The National Carbonaceous aerosol programme- Carbonaceous aerosol emissions, source apportionment and climate impacts (NCAP-COALESCE) network source emission measurement system was used to measure absorption and scattering properties using the Aethalometer and Integrating Nephelometer, respectively. Measurements were done for clamp kilns of different firing stages, namely ignition, propagation, and end. The combustion efficiency was >97% during the end, propagation and ignition stages. The average BC (SO₂) concentration measured during the ignition, propagation and end stage was 12.5 (10) 18.5 (9), and 13.3 μg-m^-3(19 ppm), respectively against background of 2 μg-m^-3 (0 ppm) . The corresponding values of average AAE_370/660 (AAE_660/880) during the three combustion phases were 3.6 (1.3), 2.6 (1.1) and 1.8 (1.2), respectively. The relatively high AAEs indicate a strong contribution by brown carbon aerosol, likely emitted from fuelwood and rice husk combustion during the ignition and propagation stages, respectively. This study would help characterise the combustion stage specific emissions. Further analysis is ongoing to understand the potential impacts on regional air quality and climate. 

Figure 1: Emission measurement setup and different position of the multi-arm during measurement based on incoming plume