The range of commercial ceramics products is large and includes bricks, roof, wall and floor tiles, refractory ceramics, sanitary ware, tableware and cookware and other products. In terms of volume, the production of bricks and tiles dominate. The main raw materials used in the brick industry include clay and kaolin. Production technologies and respective energy efficiencies vary tremendously from large industrial operations to cottage and artisan production, which are still very common in many developing countries. The main fuels used in modern industrial kilns are natural gas and fuel oil. Specific energy consumption varies considerably for different products and kiln designs. The EU-BREF Ceramics (2005) reported specific energy consumptions for modern industrial brick production of 1.4 to 2.4 GJ/t of product.
Small-scale kilns – used mainly for brick production – are often used in developing countries. Wood, agricultural residues and coal (FAO, 1993) are the main fuels used, with specific energy consumptions of 0.8 to 2.8 GJ/t of brick for the small- to medium sized kilns, and 2 to 8 GJ/t of brick for the very small-scale kilns used by cottage industries and artisans (FAO, 1993). Producers also utilize the energy contained in the organic fraction of clay and shale as well as in pore forming agents (e.g., sawdust) added to the clay in the production process. CO2 emissions from the calcination of carbonates contained in clay and shale typically contribute 20 to 50% of total emissions. The current choices of building materials and kiln technologies are closely related to local traditions, climate, and the costs of labour, capital, energy and transport, as well as the availability of alternative fuels, raw materials and construction materials.
Reliable international statistics on the production of ceramics products are not available. Consumption of bricks, tiles and other ceramic products in tonnes per capita per year is estimated at 1.2 in China (Naiwei, 2004); 0.4 in the EU (EU-BREF Ceramics, 2005), 0.1 in the USA (USGS, 2005), and 0.25, 0.12, and 0.05 for Pakistan, India and Bangladesh (FAO, 1993). This suggests that the global production of ceramic products exceeds 2 Gt/yr, leading to the emission of more than 400 MtCO2 (110 MtC) per year from energy use and calcination of carbonates. Additional research to better understand the emission profile and mitigation options for the industry is needed.
GHG mitigation options include the use of more efficient kiln design and operating practices, fuel switching from coal to fuel oil, natural gas and biomass, and partial substitution of clay and shale by alternative raw materials such as fly ash. Mitigation options could also include the use of alternative building materials such as wood or bricks made from lime and sand. However, emissions over the whole life cycle of the products including their impact on the energy performance of the building need to be considered.