Elijah Olawale Ajala

Synthesis of a catalyst (AKC-CE) from activated kaolinite clay (AKC) and chicken eggshells (CE) for biodiesel production using waste-ram-fat (WRF) was undertaken in this study. Characterisation studies of AKC, CE, and AKC-CE samples were investigated using various equipment such as X-ray fluorescence (XRF), X-ray diffraction (XRD), and High-resolution scanning electron microscope (HR-SEM) incorporated with Energy-dispersive X-ray spectroscopy (EDAX). The catalyst produced was tested for biodiesel production using WRF in a one-factor-at-a-time study of the process parameters. The XRD analysis showed that the main components of Al2(Si2O5)(OH)4, SiO2, and CaO are present in the AKC-CE catalyst. These compounds are commonly used as catalysts for biodiesel production.The AKC-CE catalyst’s morphology also demonstrated a significant cavity containing irregular crystals, with numerous white flaky crystals. These characteristics show that the catalyst would be efficient for WRF transesterification for biodiesel production. The highest biodiesel yield of 81.33% was obtained at process parameters of MeOH: WRF molar ratio of 18:1, reaction time of 4 h, catalyst loading of 10% (w/w), and temperature of 70oC. The biodiesel produced with the developed catalyst has properties within the ASTM standard. The AKC-CE catalyst is effective for producing biodiesel from WRF. Using WRF and chicken eggshells as materials for sustainable energy may not pose more threat to food availability in the biodiesel production that meets the ASTM standard as established in the Nigerian Biofuel Policy. Therefore, an increase in the use of non-edible feedstock for biofuel production is recommended.

Waste beneficiation is key to environmental protection and the realisation of a circular economy. Herein, amorphous alumina (a-Al₂O₃) derived from aluminium waste cans (AWC) was used to modify plantain stalk as an adsorbent for sequestration of lead (II) and chromium (VI) ions from electroplating wastewater. Raw plantain-stalk (RPS) and amorphous-alumina modified plantain stalk (APS) developed as adsorbents were characterised using various equipment such as x-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), and Brunauer–Emmett–Teller (BET). The FTIR revealed that the adsorbents are rich in functional groups that could promote the adsorption process which includes carboxyl, hydroxyl, and aliphatic groups. Also, the BET analysis showed a substantial increase in the surface area of APS (174.448 m²/g) compared to that of RPS (40.531 m²/g) which could be due to the effect of modification by the a-Al₂O₃. The batch adsorption studies revealed that the APS achieved 99.38% and 98.33% removal of Cr(VI) and Pb(II), respectively, which is superior to RPS adsorption efficiency. Also, the estimated and experimental data for the APS compared well under all the kinetic models studied with R² > 0.88. This suggested that chemisorption is the most plausible adsorption mechanism of Cr(VI) and Pb(II) onto the APS. Further analysis showed that the Cr(VI) and Pb(II) adsorption followed the Langmuir model with the R_L value of 0.038 and 0.999, respectively, which indicated that the two metal ions were effectively adsorbed onto the APS. Therefore, this work demonstrated that the modification of plantain-stalk with amorphous-alumina derived from AWC enhanced the characteristics of the APS and favoured its adsorption of the selected heavy metals.

Sugarcane (Saccharum officinarum) bagasse (SCB) is a biomass of agricultural waste obtained from sugarcane processing that has been found in abundance globally. Due to its abundance in nature, researchers have been harnessing this biomass for numerous applications such as in energy and environmental sustainability. However, before it could be optimally utilised, it has to be pre-treated using available methods. Different pre-treatment methods were reviewed for SCB, both alkaline and alkali–acid process reveal efficient and successful approaches for obtaining higher glucose production from hydrolysis. Procedures for hydrolysis were evaluated, and results indicate that pre-treated SCB was susceptible to acid and enzymatic hydrolysis as > 80% glucose yield was obtained in both cases. The SCB could achieve a bio-ethanol (a biofuel) yield of > 0.2 g/g at optimal conditions and xylitol (a bio-product) yield at > 0.4 g/g in most cases. Thermochemical processing of SCB also gave excellent biofuel yields. The plethora of products obtained in this regard have been catalogued and elucidated extensively. As found in this study, the SCB could be used in diverse applications such as adsorbent, ion exchange resin, briquettes, ceramics, concrete, cement and polymer composites. Consequently, the SCB is a biomass with great potential to meet global energy demand and encourage environmental sustainability.

The prospect of utilizing yam peel hydrolysate (YPH) as a carbon source for lactic acid (LA) production using Rhizopus orysae was investigated in batch surface and submerged fermentation processes. The kinetics of biomass growth, substrate utilization and LA production were studied using models of modified Luedeking–Piret, logistic and simple Luedeking–Piret equations, respectively, for the surface and submerged processes. The YPH containing 80 g L⁻¹ of reducing sugars (glucose, xylose, ribose and others) was obtained by acid hydrolysis (H₂SO₄) of 100 g L⁻¹ of yam peel and used for fermentation. The LA yield from the YPH was 80.03% and 75.63% for the surface and submerged fermentation, respectively. These values were higher than those of synthetic glucose syrup (SGS), which were 77.36% and 38.96% for surface and submerged fermentation, respectively. The models were satisfactory for the fermentation processes with high accuracy of R² ((0.89 to 0.96), (0.95 to 0.99) and (0.86 to 0.99)) for biomass growth, substrate (SGS/YPH) utilization and LA production, respectively. The models also elucidated that the fermentation process was growth associated (α) instead of non‐growth associated (β) because the value of α/β was greater than 1. This justified the other kinetic parameters obtained for the growth phase. Therefore, Rhizopus oryzae effectively converted YPH to LA with a high yield and purity. © 2021 Society of Industrial Chemistry and John Wiley & Sons Ltd

The industrial application of lactic acid is very broad; hence, the high demand is forecasted to multiply in the future. This review presented the major problems for the efficient production of lactic acid from lignocellulose biomass using lactic acid bacteria (LAB) and further proposes three promising solutions to solve these problems, exposing their potentials and future research needs. Recombinant cellulolytic strategy in LAB promises a significant reduction of lactic acid production costs, however, extensive research on genetic engineering is still needed. Microwave‐assisted deep eutectic solvent pretreatment is extremely fast and produces little to no harmful by‐products, but it has not been investigated for lactic acid production yet. Continuous simultaneous saccharification and fermentation with enzyme and cell recycle is newly proposed by the authors as a process set up that can solve the problems of feedback‐, substrate‐ and end‐product inhibition while resulting in higher lactic acid productivities, yield, and concentration.

Acid hydrolysis of cassava peel (CP) to reducing sugar (RS) was undertaken at 70, 90 and 110 °C, and 0.5, 1.0 and 1.5 M concentrations of H₂SO₄. Kinetics and thermodynamics of the study were tested for their statistical consistency using analysis of variance (ANOVA). The RS was characterised for its bioactive chemical compositions and functional groups. Maximum RS of 47.70 g/l from a 50 g/l of the CP with the highest rate constant (k) of 0.00247 min⁻¹ was attained at 1.5 M and 110 °C. The ANOVA results of F > F crit and p < 0.05 revealed that the AC at constant temperature has a significant effect on the hydrolysis. The thermodynamic analysis revealed that the highest value of 3.06 × 10³ Jmol⁻¹ for ΔH (1.5 M and 110 °C), and the lowest value of ΔS = −7.65 × 10 Jmol⁻¹ (0.5 M and 70 °C) were obtained. The bioactive chemical indicated the presence of compounds effective against several diseases. The functional groups obtained among others include alkanols, aldehyde, and alkanoates. Therefore, CP hydrolysis is a significant way of reducing the cost of RS as it contains essential ingredients for pharmaceutical, food and medicinal purposes.