Economic Feasibility of Rice Husk Ash Blended Cement: Cost, Energy and Market Impacts in Nigerian Cement Production

Abstract

Cement production contributes an estimated 7-8% of global CO₂ emissions, largely due to energy-intensive clinker manufacture. In addition, rising electricity tariffs in Nigeria and increasing cement demand highlight the urgency for low-carbon, cost-effective alternatives. Rice husk ash (RHA), an agricultural by-product rich in amorphous silica, presents a viable supplementary cementitious material capable of reducing clinker use, energy consumption, and production cost. In this study, RHA sourced from a rice mill in Offa, Nigeria, was characterized using X-ray fluorescence, X-ray diffraction, and loss-on-ignition analyses to verify chemical suitability. Portland limestone cement clinker was partially replaced with 10-50% RHA, and grinding energy was measured across incremental batches and scaled to per-ton requirements. Cost modeling incorporated clinker price (₦97,500/ton), electricity tariff (₦209.50/kWh), and a conversion factor of 21 bags per ton, while sensitivity analysis evaluated clinker prices (₦82,500.00-₦120,000.00) and electricity tariffs (₦150-₦300/kWh). RHA exhibited strong pozzolanic characteristics (SiO₂ = 84.14%; Al₂O₃ = 3.35%; Fe₂O₃= 1.02%; 73.27% amorphous content). Grinding energy decreased significantly from 221.68 kWh/ton (M0) to 104.86 kWh/ton (M50). Production cost per bag declined from ₦6,854.38 for the control to ₦3,367.53 for M50, with corresponding reductions in estimated market price from ₦9,500 to ₦6,013. Long-term compressive strength improved at moderate substitution levels, with the M30 blend achieving 68.6 MPa at 360 days, outperforming the control (67.8 MPa). Sensitivity results indicated robust cost savings of ₦850.00-₦4,200.00 per bag across market conditions. Overall, RHA-blended cements demonstrate substantial economic and environmental advantages, confirming RHA as a feasible SCM for large-scale adoption in Nigeria.