Crude glycerol is a by-product generated from biodiesel
production in the amount of 1 kg per 10 kg of biodiesel (10% w/
w) [14]. Various investigations of single stage of dark or photo
fermentation for hydrogen from crude glycerol have been reported
[15e17]. However, to the best of our knowledge, there
was no report on two stage processes of dark and photo
fermentation of crude glycerol from the biodiesel plant.