Department of Chemical Engineering, National Institute of Technology Raipur, Raipur-492 010, Chhattisgarh, India E-mail: prabirg.che@nitrr.ac.in Manuscript received online 14 April 2020, accepted 12 June 2020 The cement plant is a major CO2 emitter during the clinker manufacturing process. CO2 is mainly emitted at Calciner and Kiln due to calcination of raw materials and burning of fossil fuel. Worldwide several technologies and various measures have been taken for the reduction of CO2 in cement plant i.e. efficiency improvement of thermal and electrical energy by using alternative materials etc. In India, mainly three types of cement are produced i.e. Ordinary Portland cement (OPC), Portland pozzolana cement (PPC) and Portland slag cement (PSC) and percentage clinker for OPC, PPC and PSC are 90–95%, 30–35%, 50–70%, respectively. Chemical conversion takes place during the clinker production. Limestone (CaCO3) is converted into lime (CaO), MgCO3 is converted to MgO and carbon dioxide (CO2) is emitted during clinker manufacturing and burning of fossil fuel. Blast furnace slag is a waste of steel industries and it contains CaO, MgO and silicates etc. The CO2 emission reduction and energy efficiency improvement of the clinker manufacturing unit are investigated (M/s Emami Cement Limited, Village-Risda, Suhela Road, Baloda Bazar, Chhattisgarh) during the clinker manufacturing are around 2–4% of total raw feed. Blast furnace slag is used as elective raw materials which are fed into the kiln inlet with the help of winch machine. It is converted into the clinker and reduces the CO2 emission and fuel consumption. Blast furnace slag is already calcined due to high temperature in the furnace. The authors have investigated the CO2 emission reduction using blast furnace slag as alternativeraw material for clinker manufacturing at the earlier mentioned cement plant to conserve natural resources and also suggested the alternatives for the emission reduction using the process integration approach.