Structural optimization of biohydrogen production: Impact of pretreatments on volatile fatty acids and biogas parameters

The present study aims to describe an innovative approach that enables the system to achieve high yielding for biohydrogen (bio-H2) production using xylose as a by-product of lignocellulosic biomass processing. A hybrid optimization technique, structural modelling, desirability analysis, and genetic algorithm could determine the optimum input factors to maximize useful biogas parameters, especially bio-H2 and CH4. As found, the input factors (pretreatment, digestion time and biogas relative pressure) and volatile fatty acids (acetic acid, propionic acid and butyric acid) had significantly impacted the biogas parameters and desirability score. The pretreatment factor had the most directly effect on bio-H2 and CH4 production among the factors, and the digestion time had the most indirectly effect. The optimization method showed that the best pretreatment was acidic pretreatment, digestion time > 20 h, biogas relative pressure in a range of 300-800 mbar, acetic acid in a range of 90-200 mg/L, propionic acid in a range of 20-150 mg/L, and butyric acid in a range of 250 -420 mg/L. These values caused to produce H2 > 10.2 mmol/L, CH4 > 3.9 mmol/L, N2 < 15.3 mmol/L, CO2 < 19.5 mmol/L, total biogas > 0.31 L, produced biogas > 0.10 L, and accumulated biogas > 0.41 L. (c) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.