Carbon footprint of solid clay bricks fired in clamps of India

Abstract

Carbon footprint is broadly defined as carbon dioxide (CO2.) emissions normalized per unit mass of a product or per unit of an activity. It is considered as an important environmental indicator for comparing various products or activities. Fired solid clay brick is a popular walling material in India. Manufacturing of fired clay bricks involves combustion of fossil fuels during the firing process and during other unit operations and activities. Due to combustion of fossil fuels, dissociation of mineral calcite in the soil during the firing of green bricks and combustion of diesel during transportation of raw materials, the greenhouse gas emissions are associated with the manufacturing of fired clay bricks. About 250 billion bricks are manufactured annually in India. To fire the green bricks, mainly two types of brick kilns are used in India: Bull's trench kiln and Clamp kilns. The Bull's trench kilns are mainly used in northern and central India whereas the clamps are used in peninsular India. In the present study, carbon footprint of bricks manufactured in the clamps of a major clamp cluster in peninsular India is estimated and is compared with that of bricks manufactured in other types of kilns in India. Karad, District Satara, Maharashtra (India) located in peninsular India has a major cluster of clamp type brick kilns which has more than 300 clamp kiln sites with annual production of approximately 120 million bricks. A field survey of the clamps of Karad is conducted to collect the data about use of soil, fuels and water and its transportation. The CO2 emissions due to various unit operations and activities in a typical clamp are estimated using guidelines provided by the Intergovernmental Panel on Climate Change. These total emissions are normalized per unit mass of fired brick and are presented as carbon footprint of a brick. The statistical mean of the carbon footprints of bricks manufactured in all the surveyed clamps is presented as the carbon footprint of bricks manufactured in the clamps of Karad. The average carbon footprint of the bricks manufactured in the clamps of Karad is estimated as 195 g CO2/kg of fired brick and 162 g CO2/kg of fired brick respectively, when the CO2 emissions due to the combustion of biofuels and transportation of raw materials are included or excluded. This is comparable to the carbon footprint of the other popular brick-making technologies, and defies the common notion that clamps are highly inefficient. The carbon footprint of bricks manufactured in the clamps of Karad is lower than that reported for the clay bricks manufactured in tunnel kilns in the United States of America, Canada and the United Kingdom.