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

TL;DR

This study develops an integrated optimization approach to enhance biohydrogen and biogas production from lignocellulosic biomass, identifying key factors like pretreatment and digestion time that significantly influence yields.

Contribution

It introduces a hybrid optimization method combining structural modeling, desirability analysis, and genetic algorithms to maximize biohydrogen and biogas outputs.

Findings

Acidic pretreatment significantly improves bio-H2 and CH4 yields.

Optimal conditions include digestion > 20 hours and specific volatile fatty acid ranges.

Produced bio-H2 exceeds 10.2 mmol/L under optimized parameters.

Abstract

The present study aims to describe an innovative approach that enables the system to achieve high yielding for biohydrogen (bio-H$_2$) 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-H$_2$ and CH$_4$. As found, the input factors (pretreatment, digestion time and biogas relative pressure) and volatile fatty acids (acetic acid, propionic acid and butyric acid) had indirectly and significantly impacted the bio-H$_2$ and desirability score. The pretreatment factor had the most effect on bio-H$_2$ and CH$_4$ production among the factors, and after that, were propionic acid and digestion time. The optimization method showed that the best pretreatment was acidic pretreatment, digestion time > 20 h, 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 H$_2$ > 10.2 mmol/L, CH$_4$ > 3.9 mmol/L, N$_2$ < 15.3 mmol/L, CO$_2$ < 19.5 mmol/L, total biogas > 0.31 L, produced biogas > 0.10 L, and accumulated biogas > 0.41 L.