Fermentation of swine wastewater-derived duckweed for biohydrogen production

•We show that duckweed is a promising feedstock for biohydrogen production.•Acid pretreatment could effectively improve the fermentation yield of duckweed.•Biohydrogen production from duckweed was greater at a slightly acidic condition.•Increased salt concentrations inhibited duckweed fermentation to hydrogen.

Duckweed harvested from a swine wastewater treatment system was evaluated for its potential as a fermentation feedstock for the production of biohydrogen. The effects of pretreatment and fermentation conditions on biohydrogen production were investigated in laboratory-scale batch experiments. The results showed that mild acidic thermal pretreatment (1% H2SO4 and 85 °C for 1 h) was more effective in improving the fermentability of duckweed than either thermal or mild alkaline thermal pretreatments. Fermentation of acid-pretreated duckweed resulted in a biohydrogen production of up to 75 mL H2 per g dry duckweed in 7 days (at a H2 concentration of 42%), which is comparable with other plant biomass. Overall, the results show that small aquatic plants such as duckweed can be promising substrate for biohydrogen production.

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