Spirogyra Oil-Based Biodiesel: Response Surface Optimization of Chemical and Enzymatic Transesterification and Exhaust Emission Behavior

Abstract

Algae are emerging as a major and reliable source of renewable biodiesel that could meet the energy requirements of the world. Like plants, algae produce and store oils in their cells. Algal samples were collected from Gujrat District, Pakistan, their oil content was analyzed, and the best oil producing alga was identified as Spirogyra crassa. After collecting sample, oil was extracted using the Soxhlet extraction method. Spirogyra oil was characterized physico-chemically for the evaluation of its quality. Acid value, density, saponification value, peroxide value, as well as viscosity and iodine values were determined and their values were 16.67 ± 3.53 mg KOH/g, 0.859 ± 0.050 g/cm3, 165.33 ± 13.20 mg KOH/g, 4.633 ± 0.252 meq/kg, 5.63 ± 0.833 mm2/mL, and 117.67 ± 13.01 mg I2/g, respectively. Chemical as well as enzymatic transesterification protocols were employed for biodiesel production using NaOCH3 and NOVOZYME-435, respectively. Different reactions parameters involved in transesterification were optimized by the response surface methodology. The optimized yield of biodiesel (77.3 ± 1.27%) by the chemical transesterification of algal oil (spirogyra) was observed by carrying out the reaction for 90 minutes at a reaction temperature of 45 °C using 1.13% catalyst (NaOCH3) concentration and 6:1 methanol:oil. Meanwhile, for enzymatic transesterification, the optimized yield (93.2 ± 1.27%) was obtained by conducting the reaction for 42.5 h at the temperature of 35 °C using 1% enzyme concentration and 4.5:1 methanol:oil. Fuel properties, including flash point, pour point, cloud point, fire point, kinematic viscosity, and density, were determined and their values are 125.67 ± 2.11 °C, −19.67 ± 0.8 °C, −13 ± 1 °C, 138.667 ± 2.52 °C, 5.87 ± 2.20 mm2/mL, and 0.85 6 ± 0.03 g/cm3, respectively. Fourier transfer infrared spectroscopic (FTIR) and Gas chromatography with flame ionization detector (GC-FID) analysis were performed for the monitoring of the transesterification process and fatty acid methyl acid (FAME) profiling, respectively.

Evaluation of a New Cerium Oxide-Bismuth Oxide-Based Nanobiocomposite as a Biocatalyst for Biodiesel Production

“…The normal data distribution points in normality plot without any strong outliers is indicative of the suitability of the quadratic model. Moreover, the similar predicted and actual values also supports the validity of the quadratic model for biodiesel yield data [3]. The validity of the quadratic model was also verified from the normality plot of residuals and predicted vs. actual plot (Figure 8).…”

“…In contrast, the enzyme-catalyzed trans/esterification is becoming the preferred biodiesel production method due to the following advantages over the chemical method: ambient process conditions, lower treatment costs, reusable and renewable catalyst, superior substrate specificity, one-step conversion of triglycerides and FFA to biodiesel, lower alcohol to oil ratio, prevention of side reactions, less impurities, easier biodiesel separation, and fewer environmental concerns [3].…”

“…The lipase immobilization is an environmentally friendly and economically advantageous process that is associated with lower energy consumption, broader feedstock specificity, and reduced post-treatment handling cost. The methods for enzyme immobilization include adsorption, physical entrapment, bio-conjugation and covalent immobilization [3].…”

Microalgal–bacterial consortia for efficient wastewater treatment: Optimization using response surface methodology

“…The R 2 values of COD RE, NH 3 ‐N RE, TP RE, and biomass growth rate were 0.8581, 0.8751, 0.9800, and 0.8952, respectively, which are basically consistent, indicating that the equation can well reveal the relationship between the reliable conditions and the reaction. R 2 values were close to 1, indicating that these equations were closed to accuracy (Sohail et al, 2020). As shown in the rundown of experimental results acquired under various ambient condition and aeration, the highest predicted values of COD RE, NH 3 ‐N RE, TP RE, and biomass growth rate were 95.43%, 89.42%, 99.63%, and 95.49% with illumination intensity 5000 lx, photoperiod 12 h, and aeration 0.55 L min −1 (see Figure 1).…”

“…The 3D plots and contour-line pots of the quadratic model were formed by maintaining aeration at the central level and altering the other two conditions (illumination intensity and photoperiod) within their ranges. The objective of optimization is to ensure maximum production possible by minimizing the associated cost without compromising the efficiency of MBC (Sohail et al, 2020).…”