Cement clinkerisation is the major energy-consuming process in cement manufacturing due to the high-temperature requirement. In this paper, energy data including specific energy consumption, forms, and types of energy used at different units of cement manufacturing processes were analyzed and compared for effectiveness, availability, cost, environmental, and health impact. Data from three different cement industries in Nigeria labeled as A, B, and C were used for the analysis in this study. The results of this research work established that coal is the cheapest energy source but environmental issues exonerate it from being the choice energy source. LPFO and Natural gas give better production output while minimizing pollution and health issues. When benchmarked against each other, Factory B was found to be the most energy-efficient in terms of output and cost of production. Although coal is cheaper compared to fuel oil and supposed to contribute a share of fuel used in cement industries, the industries are moving towards the use of alternative and conventional fuels to reduce environmental pollution. It is therefore recommended that deliberate effort to achieve appreciable energy-efficient levels should be the priorities of the cement industries in Nigeria.

In this study the process flow diagram for the cement production was simulated using Aspen HYSYS 8.8 software to achieve high energy optimization and optimum cement flow rate by varying the flow rate of calcium oxide and silica in the clinker feed. Central composite Design (C.C.D) of Response Surface Methodology was used to design the ten experiments for the simulation using Design Expert 10.0.3. Energy efficiency optimization is also carried out using Aspen Energy Analyser. The optimum cement flow rate is found from the contour plot and 3D surface plot to be 47.239 tonnes/day at CaO flow rate of 152.346 tonnes/day and the SiO2 flow rate of 56.8241 tonnes/day. The R2 value of 0.9356 determined from the statistical analysis shows a good significance of the model. The overall utilities in terms of energy are found to be optimised by 81.4% from 6.511 x 107 kcal/h actual value of 1.211 x 107 kcal/h with 297.4 tonnes/day the carbon emission savings.

The drying kinetics of Clerodendrum Volubile leaves was investigated at different temperature of 50, 60 and 70⁰C in oven dryer. The weight loss with time was recorded and moisture ratio was computed and fitted into different eleven thin-layer drying models. The result showed that moisture ratio reduces with time for all drying temperatures. The drying rate was observed to increase with temperature peaking at 0.185, 0.117 and 0.059 g H2O/g dry solid.min at 70, 60 and 50⁰C respectively. Drying occurred in falling rate period and no constant rate period was observed. The approximation of diffusion model was observed to give the best fit model for the drying process with highest coefficient of determination (0.9985), lowest sum of square errors (0.0032), reduced chi square (0.00012) and root mean square error (0.0107) occurring at 50 ⁰C. The effective diffusivity for Marugbo drying increases with temperature from 3.65×10-12 to 1.28×10-11 m2/s. The Arrhenius equation also described the temperature dependence of diffusivity with activation energy of 57.74 kJ/mol.

In this study, a five-year (2010-2014) production and energy utilisation data in a sausage producing company in Nigeria was analysed for energy consumption, energy intensity, energy productivity, cost of energy per unit product and Normalized Performance Indicator (NPI). The average annual energy consumption was 15,853.22 GJ. The energy consumption mix was 27.66% PHCN main, 32.06% diesel generators and 40.28% oven gas. Main electricity supply from utility company contributed to 25.04% of the total energy cost while diesel was 44.24% and oven gas was 30.71% of the total cost. The average production output from the factory was 595,700 tonnes and the average cost of energy input was 6.71 kobo/kg for the five-year period. The values of cost of energy input per unit product showed a decreasing trend for the five years. The energy intensity also increased through the study years with an average of 1.67 GJ/m 2 while the energy productivity decreased throughout the years with an average of 28.3 kJ/kg. The Normalized Performance Indicator (NPI) values calculated for the five years showed steady increment with an average of 1.61 GJ/m 2 . This indicated a "very poor" range which implies an excessive energy usage, immediate action should be taken to investigate and remedy this.

Energy security, cost of production and environmental constraints have necessitated the need for proper energy utilisation in the manufacturing industries. This work analysed energy and production data from an aluminium extrusion plant in Lagos, Nigeria for energy efficiency, exergy efficiency (or process efficiency), energy cost per unit of production, CO 2 emission and pollution rate index. The input-output energy analysis method was used to estimate the embodied energy intensity. The pollution rate, energetic and exergetic efficiencies were estimated from the exergy analysis. The CO 2 emission was estimated from IPCC guideline on greenhouse inventories and the energy cost of unit produce was estimated from energy cost accounting method. The five-year average thermal and electrical utilisation ratio was 45/55, which deviated from the 70:30 of the global best practices. The embodied energy intensity for the five years' ranges between 2.31-162.3 GJ/t which is in excess of the recommended range of (2.9-3.2 GJ/t). The mean energy efficiency for the five year was 79.4% and the mean exergetic efficiency was 57.8% indicating that production was well managed (>50%) with energy wastages very high in boiler energy conversion. The total energy used was 16 MJ and CO 2 emitted is 1.01 × 10 11 g during the study period. The average pollution rate index for the plant was 0.8695 indicating that the plant is negatively impacting the environment due to technological limitation of the energy conversion process employed in the manufacturing plant. The study reveals a distortion of the recommended best practice in energy balance ratio which accounted for the high average cost of production (₦ 4418.3/t); process efficiency was generally low thereby negatively affecting industrial output for the company.