Biological production of hydrogen from crude glycerol under thermophilic conditions
TL;DR
Thermophilic bacteria from the genera Coprothermobacter and Thermoanaerobacterium were favored by the imposed operating conditions, acting synergistically in the thermophilic fermentative metabolic pathways of H2 generation from crude glycerol.
Abstract
ABSTRACT Glycerol is the main residue in biodiesel production. A viable alternative is its application in anaerobic digestion for hydrogen production. Thermophilic conditions can favor biogas generation from glycerol, by anaerobic digestion, with advantages in microorganism selectivity and low biogas solubility in liquid phase. Therefore, this study evaluated the bioconversion potential of crude glycerol into H2, using a thermophilic granular sludge, in anaerobic batch reactors operated at 55°C, at initial pH 5.5 or 6.0 in 5 experiments containing (g L-1) glycerin (10.0) or crude glycerol (5.8) in different culture media with additions of peptone; meat extract and yeast extract. High glycerin removal (92.4–97.5%) was observed in all experiments, resulting in hydrogen production of (mmol L−1) 47.81, 24.19, 51.48, 43.17 and 15.43; yields of (mol H2 mol glycerin consumed-1) 1.36; 0.75; 1.48; 1.30 and 0.48 in the experiments 1, 2, 3, 4, and 5, respectively. Metagenomic analysis revealed that thermophilic bacteria from the genera Coprothermobacter and Thermoanaerobacterium were favored by the imposed operating conditions, acting synergistically in the thermophilic fermentative metabolic pathways of H2 generation from crude glycerol. Thermophilic anaerobic digestion of crude glycerol is an alternative for its treatment, resulting in the generation of biofuels such as H2.