Simultaneous biohydrogen production from dark fermentation of duckweed and waste utilization for microalgal lipid...

A cost-effective and environmentally friendly method for biofuel production was developed, by utilizing duckweed as feedstock for biohydrogen production through dark fermentation and simultaneously using the fermentative waste to produce microalgal lipids. The results suggested that acid hydrolysis (1% H₂SO₄) was more suitable for the pretreatment of duckweed biomass. Maximum hydrogen production of 169.30 mL g^-1 dry weight was determined under a temperature of 35 °C and an initial pH of 7.0. After the dark fermentation, the volatile fatty acids (VFAs) including acetate and butyrate, were detected in the waste, with concentration determined as 1.04 g L^-1 and 1.52 g L^-1, respectively. During the mixotrophic cultivation of Chlorella sacchrarophila FACHB-4 using waste as feedstock, the maximum microalgal biomass and the lipid productions were about 2.8 and 33 times higher with respect to the autotrophic growth. The simultaneous biohydrogen production and waste utilization method provided a green strategy for biofuel production.