Producing hydrogen from the fermentation of cheese whey and glycerol as cosubstrates in an anaerobic fluidized bed reactor

Abstract

This study aimed to evaluate the effect of the organic loading rate (OLR) (60, 90, and 120 g Chemical Oxygen Demand (COD). L −1 . d −1 ) on hydrogen production from cheese whey and glycerol fermentation as cosubstrates (50% cheese whey and 50% glycerol on a COD basis) in a thermophilic fluidized bed reactor (55 °C). The increase in the OLR to 90 gCOD.L −1 . d −1 favored the hydrogen production rate (HPR) (3.9 L H 2 . L −1 . d −1 ) and hydrogen yield (HY) (1.7 mmol H 2 . gCOD −1 app ) concomitant with the production of butyric and acetic acids. Employing 16S rRNA gene sequencing, the highest hydrogen production was related to the detection of Thermoanaerobacterium (34.9%), Pseudomonas (14.5%), and Clostridium (4.7%). Conversely, at 120 gCOD.L −1 . d −1 , HPR and HY decreased to 2.5 L H 2 . L −1 . d −1 and 0.8 mmol H 2 . gCOD −1 app , respectively, due to lactic acid production that was related to the genera Thermoanaerobacterium (50.91%) and Tumebacillus (23.56%). Cofermentation favored hydrogen production at higher OLRs than cheese whey single fermentation. • The organic loading rate was evaluated in a thermophilic fluidized bed reactor. • Cofermentation of cheese whey and glycerol was suitable for bio-H 2 production. • A higher H 2 yield of 1.7 mmol. gCOD −1 app was observed at 90 gCOD.L −1 . d −1 . • The highest H2 yield was concomitant with butyric acid (41.1% molar) production. • Thermoanaerobacterium was the main genus involved in H 2 production.