Fermentation of Chlorella sp. for anaerobic bio-hydrogen production: Influences of inoculum-substrate ratio, volatile fatty acids and NADH

► Influences of inoculum-substrate ratio (ISR) and volatile fatty acids (VFAs) on anaerobic hydrogen production were studied. ► The role of nicotinamide adenine dinucleotide, the reduced form (NADH) were also investigated. ► ISR and NADH were negative relation with H2 yield, while VFAs had a positive correlation with hydrogen production. ► The maximum hydrogen production from degrading Chlorella sp. achieved by 7.13 mL/g VS at the ISR value of 0.3.