Modeling and Optimization of Process Conditions Influence on Glucose, Xylose and Bioethanol Yield From Lignocellulosic Waste Palm Fruit Bunches

This study examined the effect of processing parameters (acid concentration, temperature and process duration) on the yield of glucose, xylose and bioethanol synthesized from lignocellulosic waste palm fruit bunches. Raw material was procured from a palm oil processing company in Port-Harcourt, Nigeria. It was mechanically communited, characterized and hydrolyzed using different concentrations of H2SO4, temperatures and resident times. Hydrolysates were tested for xylose and glucose yield using a spectrophotometer Hydrolysates were then fermented at room temperature for different time duration using Saccharomyces sereviciae. Hydrolysis and fermentation processes were modeled and optimized using the RSM. A laboratory distiller was used to purify the bioethanol obtained, and the proximate composition and fuel properties were determined. Results showed that the feedstock had a composition of 74.33 % holocellulose, (57.44 % α-cellulose and 16.89 % hemicelluloses), 15.87 % lignin and 5.57 % ash. RSM polynomial of the quadratic form adequately expressed the relationship existing between process variables and yield of glucose, xylose, and bioethanol with R2 and SEE ranging from 0.963 to 0.993 and 0.121 to 2.501, respectively. Optimum glucose and xylose yield was 34.643g/L and 18.471g/L, at 1.196 and 1.195% acid load hydrolysis for 26.924 and 21.578 mins at 160.407 and 160.071oC, respectively. Optimum bioethanol yield of 32.838 g/L was obtained at 72.933h and 86.15% fermentation efficiency. The bioethanol had 97.68 % purity, 0.03 % ash, 0.42 % moisture content, 5.05 mg/L acidity, and 6.61 pH. The fuel properties were 791.13 kg/m3 density at 15oC, 1.67 mm/s2 viscosity at 40oC, 124 Octane Number, 13.043 kPa vapour pressure, 12.8oC flash point, 79 - 101oC distillation temperature range, 358oC auto-ignition, 29.16 MJ/kg calorific value, and 589.51oC drivability index. Proximate composition of the bioethanol satisfied the ASTM D4806 specification, its fuel properties met the International Standard, therefore, it can be blended with pure petrol for use in spark ignition engines.