CHEMICAL ENGINEERING

The global shift toward sustainable energy has intensified interest in biodiesel as an environmentally friendly alternative to fossil fuels. This study investigates the production of biodiesel from waste cooking oil (WCO) using calcined heterogeneous catalysts derived from waste materials, including pumpkin pods and turkey bones, and its subsequent preservation using natural extracts from Azadirachta indica (neem) and Ocimum gratissimum (African basil). Transesterification was carried out in a pilot-scale reactor at 60 °C for 75 minutes. Characterization of the WCO prior to transesterification showed an acid value of 2.41 mg KOH/g and a free fatty acid (FFA) content of 1.21%, indicating moderate degradation from repeated frying. Post-treatment analysis revealed a slight increase in acid value to 3.07 mg KOH/g, while other parameters, including saponification value (251.83 mg KOH/g), density (0.8948 g/cm³), and viscosity (9.50 mPa·s), remained within acceptable ranges for biodiesel feedstock. The produced biodiesel met key ASTM D6751 specifications, with a density of 0.87 g/cm³, acid value of 0.34 mg KOH/g, viscosity of 4.62 mm²/s, and a flash point of 220 °C, confirming its suitability for use as a fuel or in blends. GC-MS analysis revealed a fatty acid methyl ester (FAME) composition dominated by methyl oleate (48.68%) and methyl palmitate (37.48%). FTIR spectroscopy further confirmed successful transesterification through the presence of a characteristic ester carbonyl absorption peak at 1742.81 cm⁻¹. Stability studies conducted over six weeks showed that the combined treatment of neem and basil extracts (30 ml) resulted in the lowest final acid value of 0.78 mg KOH/g, indicating improved oxidative stability. This study demonstrates that waste cooking oil is a viable and cost-effective feedstock for biodiesel production. Furthermore, the use of locally sourced plant extracts as natural stabilizers offers a sustainable and biodegradable approach to enhancing biodiesel storage stability, supporting the advancement of renewable energy technologies in Nigeria.

Androgenetic alopecia (AGA), a gradual form of hair loss driven by oxidative stress and hormonal imbalance, remains a major dermatological issue. Conventional synthetic treatments often lead to undesirable side effects, creating the need for safer, plant-based alternatives rich in bioactive compounds that can promote hair regrowth and scalp health. This study aimed to investigate the extraction, optimization, and characterization of bioactive compounds from Syzygium aromaticum (clove), Rosmarinus officinalis (rosemary), and Moringa oleifera (moringa) for potential application in natural formulations targeting androgenetic alopecia.Extraction was optimized using a mixture design approach in Design Expert® software, where the proportions of the three plant materials were systematically varied to maximize total phytochemical yield. The experimental data were fitted into a quadratic model that exhibited strong predictive accuracy with an R² value of 0.9633, while the predicted and adjusted R² values were closely aligned, 0.9268 and 0.9560 respectively, confirming the model’s reliability and significance (p < 0.0001). Optimization results showed that the best formulation was gotten using 3.553 g of cloves, 2.389 g of rosemary, and 4.057 g of moringa, yielding 15.108 with a maximum desirability value of 1.000. Phytochemical screening and quantitative analysis revealed that the optimized blend possessed very high concentrations of phenols, flavonoids, terpenoids, and steroids. Fourier Transform Infrared (FTIR) spectroscopy further confirmed the presence of crucial functional groups such as hydroxyl (–OH), carbonyl (C=O), and C–O linkages, characteristic of polyphenolic and terpenoid compounds.The results indicated that the combined extract showed synergistic phytochemical enrichment, suggesting improved bioactive potency. The dominance of phenolic and flavonoid compounds implies strong antioxidant and 5α-reductase inhibitory potential, thereby reducing dihydrotestosterone (DHT)-induced follicular shrinkage. Terpenoids and steroids were also found to contribute to follicular nourishment and stimulation of keratinocyte activity, enhancing overall hair growth. In conclusion, the optimized mixture of Syzygium aromaticum, Rosmarinus officinalis, and Moringa oleifera extracts exhibited promising bioactive and functional properties, supporting its potential as a natural therapeutic formulation against androgenetic alopecia.

The increasing global demand for renewable and sustainable energy sources has intensified research into bioethanol production from non-food lignocellulosic biomass. This study investigates the production of bioethanol from oil palm trunk (OPT), an abundant agricultural residue generated during replanting cycles in oil palm plantations in Nigeria, to optimize pretreatment and fermentation conditions to maximize fermentable sugar yield and ethanol production efficiency.
Oil palm trunk samples were collected from Idogbo, Benin City, Nigeria, and processed through size reduction, drying, and sieving to a 500 µm particle size. Chemical composition analysis confirmed that OPT contains 29 to 45% cellulose, 12 to 29% hemicellulose, and 18 to 23% lignin, validating its suitability as a second-generation bioethanol feedstock. Pretreatment was carried out using dilute sodium hydroxide (NaOH) at a concentration of 20% to disrupt the lignocellulosic matrix and enhance cellulose accessibility for enzymatic hydrolysis. Response Surface Methodology (RSM) based on a Box-Behnken design was employed to optimize three key pretreatment variables, namely acid concentration (1 to 6%), reaction time (10 to 120 minutes), and temperature (30 to 120°C), with fermentable sugar yield as the response variable. A total of 17 experimental runs were conducted, and the results were fitted to a quadratic model. Analysis of variance (ANOVA) confirmed the statistical significance of the model, with an F-value
of 115.99 and a p-value of less than 0.0001. The model demonstrated excellent predictive accuracy,
with a coefficient of determination (R²) of 0.9933, an Adjusted R² of 0.9848, and an Adequate Precision ratio of 28.27, confirming a strong signal-to-noise ratio and reliable navigability of the design space. Acid concentration (A), reaction time (B), temperature (C), their interaction terms (AB and BC), and quadratic terms (A², B², and C²) were all identified as statistically significant factors influencing sugar yield (p less than 0.05).
The optimum pretreatment condition was established at an acid concentration of 3.5%, a temperature of 120°C, and a reaction time of 120 minutes, yielding a maximum fermentable sugar concentration of 553.54 mg/g. Three-dimensional response surface plots demonstrated that sugar yield increased progressively with moderate acid concentration and rising temperature, but declined at extreme values due to thermal and acid-induced sugar degradation and the formation of inhibitory compounds, including furfural and hydroxymethylfurfural (HMF). Enzymatic hydrolysis of the pretreated OPT biomass was performed using commercial cellulase enzymes, followed by fermentation with Saccharomyces cerevisiae. Fermentation performance was monitored over four days using the 3,5-dinitrosalicylic acid (DNS) colorimetric method at 610nm. Sugar concentration decreased progressively from 3.8 mg/g on day one to 0.405 mg/g by day four, confirming active microbial metabolism and efficient conversion of released fermentable sugars into ethanol.
The findings of this study demonstrate that oil palm trunk is a technically viable and sustainable lignocellulosic feedstock for second-generation bioethanol production. The optimized pretreatment conditions effectively balanced lignin disruption and cellulose preservation, maximizing sugar recovery while minimizing inhibitor formation. The results support the potential of OPT waste valorization as a pathway toward renewable energy generation, reduced agricultural waste burden, and enhanced energy security in palm oil-producing regions of Nigeria. Future work
should focus on co-culture fermentation systems capable of utilizing both hexose and pentose sugars, detailed techno-economic analysis, and life-cycle assessment to establish the commercial and environmental viability of large-scale OPT-based bioethanol production.

With Nigeria generating over 42 million tonnes of waste annually, improper disposal poses significant risks to soil health, groundwater, and public health. This study examines the contamination levels of heavy metals and the physicochemical properties of soil at a solid waste disposal site in Ovia Northeast, Edo State, Nigeria. Soil samples were collected at varying depths (10, 20, 30, and 40 cm) from a dumpsite and a control site, focusing on lead (Pb), iron (Fe), copper (Cu), and manganese (Mn), alongside properties such as pH, bulk density, porosity, organic matter, and electrical conductivity (EC). Results revealed elevated levels of heavy metals at the dumpsite compared to the control site, particularly in the top 10 cm of soil. For example, Pb concentrations reached 12.31 mg/kg at the dumpsite, nearly three times higher than the 4.24 mg/kg observed at the control. Similarly, copper (Cu) levels at the dumpsite peaked at 74.22 mg/kg, significantly higher than the control site’s 57.47 mg/kg. Physicochemical properties demonstrated a strong influence on metal mobility: soil pH at the dumpsite ranged from 7.12 to 7.62, slightly higher than the control’s 6.86 to 6.12. Organic matter content decreased with depth, from 8.74% at the surface to 3.15% at 40 cm in the dumpsite, compared to 9.07% to 2.54% in the control. EC values were markedly higher at the dumpsite (252–290 µS/cm) compared to the control (144–168 µS/cm), reflecting leachate infiltration and ion enrichment. The findings underscore the environmental risks posed by heavy metal contamination, including soil degradation, reduced fertility, and potential bioaccumulation in the food chain. Elevated metal concentrations exceeded WHO permissible limits, necessitating immediate remediation actions. Recommendations include the implementation of sustainable waste management practices, soil remediation techniques such as phytoremediation, and ongoing monitoring to mitigate long-term environmental impacts.

This research examined the optimization of microwave-assisted biodiesel synthesis from neem oil by utilizing a bifunctional catalyst derived from waste cow bone and rice bran. The bifunctional catalyst was developed by combining the acid and basic precursors to facilitate simultaneous esterification and transesterification reaction. Rice bran was carbonized and treated with 1.5 M H₂SO₄ to produce the acid precursor, while cow bone was calcined and treated with 1.5 M KOH to produce the basic precursor. These precursors were then combined incorporating the wet impregnation technique. Neem oil characterization revealed an acid value of 17.67 mg KOH/g, a free fatty acid (FFA) content of 8.835%, a saponification value of 196.35 mg KOH/g and a calculated molecular weight of 941.91 g/mol showing that it is suitable for a high FFA feedstock that requires a bifunctional catalytic approach. Response Surface Methodology (RSM) was used for process optimization in order evaluate the effects of key reaction variables and identify the ideal conditions for optimizing biodiesel yield.

Heavy metal pollution has become a critical environmental challenge, particularly due to the persistence and toxicity of metals such as copper in aquatic ecosystems. Conventional treatment methods for metal removal, including chemical precipitation, ion exchange, and membrane filtration, are often costly, inefficient at low metal concentrations, and produce secondary waste. In response, biosorption has emerged as an eco-friendly and sustainable alternative. This study investigates the potential of corn cobs, an abundant agricultural by-product, as a low-cost biosorbent for the removal of Cu2+ ions from aqueous solutions. The biosorbent was prepared through collection, washing, drying, crushing, and sieving of corn cobs to obtain uniform particle sizes. A Box-Behnken Design (BBD) under the Response Surface Methodology (RSM) framework was employed to optimize process parameters such as adsorbent dosage, contact time, and metal concentration. Experimental data were fitted to a quadratic model, and statistical analysis through ANOVA revealed that the model was highly significant (F-value = 116.31 , P < 0 .0001) with strong correlation coefficients (R2 = 0.9934, Adjusted R2 = 0.9848, Predicted R2 = 0.9135). Optimization results indicated maximum copper ion removal of 94.73% at the optimal conditions of 5.5g/L adsorbent dosage, 67.5 minutes contact time, and 6 mg/L initial metal concentration. The model validation confirmed close agreement between predicted and experimental results, demonstrating the reliability of the developed model. Thermogravimetric and differential thermal analyses (TGA/DTA) suggested that the corn cob biosorbent possessed good thermal stability, which supports its suitability for adsorption applications. The study concludes that corn cobs are an effective, sustainable, and economical biosorbent for copper ion removal from wastewater. It further recommends their potential application in small- to medium-scale industrial effluent treatment systems. Future research should focus on kinetic and isotherm modeling, column adsorption studies, and biosorbent modification to enhance adsorption efficiency and extend applicability to other heavy metals.

The global depletion of fossil fuels and rising environmental concerns have intensified research into renewable and sustainable fuel alternatives. This study investigates the performance characteristics of a 20 percent biodiesel and 80 percent petrol diesel blend (B20) as a potential substitute for diesel fuel in compression ignition engines. The Waste Cooking Oil was collected, pretreated through acid-catalyzed esterification to reduce its free fatty acid content, blended with conventional diesel, and characterized based on viscosity, density, flash point, calorific value, and cetane number. Its suitability was assessed through comparison with biodiesel standards and published experimental data. The waste cooking oil was esterified to reduce its free fatty acid content before blending and laboratory analyses were conducted to evaluate the physicochemical properties of the 20:80 blend. Engine performance indicators such as brake power, fuel consumption, brake thermal efficiency (BTE), and exhaust gas emissions were carried out and results were compared with literature based datas. The results from the findings revealed that the blends achieved a progressive yield with the B20 blend achieving the most stable yield with a calorific value of 42.05 MJ/kg, density of 0.8624, and a fuel consumption rate of 1316.64 g/hr, indicating a close match with conventional diesel fuel. The B20 blend also demonstrated improved brake thermal efficiency and lower emissions, particularly in nitrogen oxides (NOx) and sulfur dioxide (SO₂), due to enhanced combustion
from biodiesel’s oxygenated structure. This establishes the fact that the biodiesel-petrol blends, particularly the B20 is a technically viable, cost-effective, and environmentally sustainable alternative to petrol diesel.

Carbon dioxide is one of the major greenhouse gas that causes global warming, it is emitted from the burning of fossil fuels in industries, power plant and vehicles. Greenhouse gases leads to increased global warming and affects the balance of the environment and pollution of the environment. Fossil fuels are the primary source of global energy which make up over 80% of consumption, the remaining 20% which is contributed by nuclear and renewable energy sources. (Holechek et al., 2022). Carbon
dioxide is the main product which is generated from combustion processes in most industries. The emission of CO2 has increased in decades. By 2021, approximately 47% of emissions were generated from electricity and heat and around 25% was from transportation (i.e. vehicles). Industries (e.g. chemicals, petrochemicals, iron and steel, aluminium, cement or paper) generates about 18% of the total CO2 emission was generated(Ochedi et al., 2020).

The potential of calcined agrowastes particularly chicken eggshells (CES) impregnated with ripe plantain peels (RPP) as a suitable catalyst for the conversion of waste cooking oil to biodiesel (FAME) by trans-esterification was investigated. The catalyst derived from these agro-wastes was synthesized by dry impregnation using physical mixing. The free fatty acid (FFA) content of waste cooking oil used for transesterification was measured to be 0.131%. The reaction conditions with methanol to oil molar ratio of 6:1, reaction time of 90 minutes, catalyst loading of 2% oil weight and a temperature of 60°C was kept constant while the catalyst’s design mixing ratios of ‘RPP: CES’ was varied. The FT-IR, XRD and elemental analysis by XRF revealed the catalytic action of these materials (RPP and CES) is a result of their metallic content (K+ and Ca 2+ ) and their microstructural formation change is noticeable when calcined at above 700°C. The experiment was carried out by the trans-esterification of the oil using each of the different designed catalyst samples to investigate the influence of their different mixing ratios on biodiesel yield. The results of the chart plots using Microsoft Excel 2010 showed that the optimum biodiesel yield consistent with ASTM D-6751 and EN 14214 standards was 75.04 % and the catalyst mixing ratio of 1:3 by mass was the optimal design ratio

Fatty acid alkyl esters are produced by subjecting vegetable or animal fats to a transesterification process with a low molecular weight alcohol, using a suitable catalyst. This process creates biodiesel, often referred to as 'green fuel', due to its numerous advantages such as biodegradability, renewability, reduced toxicity, higher cetane number, and flash point. Consequently, biodiesel has gained recognition as a potential substitute for conventional petroleum-based diesel (Baig and Ng 2010). In the majority of current biodiesel production methods, which employ homogeneous catalysis, refined vegetable oils serve as the primary raw materials. However, these refined oils come at a considerable expense. The cost of these feedstocks significantly affects the economic aspects of biodiesel production, as highlighted in a review conducted by Marchetti and Gebremariam, (Akhabue et al. 2020) discovered that the economics of biodiesel production are notably affected by the expense of feedstocks. Studies have indicated that the expenditure on raw materials for biodiesel production may make up as much as 88% of the total production expenses. Therefore, a substantial rduction in the production cost of biodiesel can be achieved through the utilization of non-edible oils or waste cooking oil (Haas et al. 2016). The elevated levels of free fatty acids (FFA) in waste cooking oil and various non-edible oils lead to saponification by the alkali catalyst, resulting in a r duced biodiesel yield due to the challenge of separating the product. Moreover, the purification process generates waste water, causing environmental pollution concerns, which require the treatment of waste water before disposal or reuse (Daud et al. 2015). This, in turn, adds to the cost of biodiesel production