Cement Manufacturers Association

20 Cement also generates most emissions per revenue dollar as indicated in Fig. 1 Figure 1 kg of CO 2 emissions per unit dollar Cement manufacturing is an energy intensive process with high fuel and electricity consumption; energy costs account for 40-45% of the production costs of cement. The cement manufacturing process releases carbon dioxide from the calcination process, fuel combustion and also indirectly from the usage of electricity. The production of clinker is responsible for the major carbon emissions. Cement producti on accounts for 83% of total energy use in the production of minerals and 94% of CO 2 emissions. Fig. 2 highlights the percentage of CO 2 emissions stagewise in cement production. The production of “clinker” acounts for most of the CO 2 emissions of cement production Figure 2 CO 2 emissions of Cement production Cutting down Carbon emissions is our primary responsibility. It is crucial to focus on the steps which generate highest CO 2 and target them for reducing the emissions by implementing various methods. The methods to utilize and implement usage of alternative resources shall also help reduce carbon emissions. 2. Recent Developments and Methods This section discusses the methodology and alternative resources that can be adopted to reduce carbon emissions and embrace sustainability in cement production. 2.1. Blended Cement Blended Cement consists of OPC partially substituted by supplementary cementitious materials (SCM) like commonly used Fly ash/ pozzolana and Ground Granulated Blast Furnace Slag (GGBS)/ Slag. Fly ash is a waste residue obtained from thermal power plants while GGBS is a by-product of Steel making process. Blended cement improves the strength and durability of concrete. The increase in Fly ash and Slag (GGBS) availability and exponential rise in market demand, has increased the production of blended cement in India. Portland Pozzolana Cement (PPC), Portland Slag Cement (PSC) and Composite Cement are produced widely by blending the OPC clinker with suitable SCM in appropriate proportion. PPC and PSC are blends of cement clinker with Fly ash and GGBS or Slag respectively. Comparison and details of GGBS and Flyash are mentioned in Table 2. Parameter GGBS Flyash Source Blast furnace of Steel industry Thermal Power plants Production Process Very stringent and in controlled process Not as stringent as in case of Steel/Iron manufacturing Conforming IS code IS 16714:2018 IS 3812: 2013 Hydration Hydraulic Pozzolonic Permissible replacement 25-70% 15-35% Table. 2 Comparison of Flyash and GGBS The chemical composition of GGBS is on similar lines compared to OPC as it has higher lime and silica content. A comparison of Chemical composition is mentioned in Table 3. • Quarring & transport of materials • Grinding & preparation of raw materials • Cooling, grinding, mixing Clinker production Less than 10% Process emissions More thand 50% Thermal emissions 40% Cement Chemicals Iron and steel Oil and gas Mining 6.9 0.3 1.4 0.4 0.8