Co-fermentation of Lemna minor with glucose and Diospyros kaki peels for hydrogen production

Abstract

Batch hydrogen gas production by co-fermentation of Lemna minor with glucose and Diospyros kaki peels was investigated. Box-Wilson statistical experiment design was used to confiGüre the experiments. The aim was to determine the most suitable Lemna minor-glucose and Lemna minor-Diospyros kaki peel concentration blends resulting in the most convenient hydrogen production yield and rate. Two sets of experiments were performed. For the first set of experiments, most convenient hydrogen yield (77.34 mL H-2/10 mL) and rate (10.82 mL H-2/h) were obtained by blending 40 g/L Lemna minor with 21 g/L glucose. Higher glucose concentration than 21 g/L at 40 g/L fixed Lemna minor caused substrate inhibition. For the second set of experiments, blending 40 g/L Lemna minor with 60 g/L Diospyros kaki peels resulted in maximum hydrogen yield and rate of 125.35 mL H-2/10 mL and 26.95 mL H-2/h, respectively. Increasing the blend concentration of Diospyros kaki peels at fixed Lemna minor concentration did have an increasing effect on hydrogen yield and rate. The total sugar concentration did not exceed 21 g/L within the inspected ranges during the second set of experiments; therefore, 40 g/L Lemna minor was blended with 123 g/L Diospyros kaki peels which provided 21 g/L total sugar, and the maximum hydrogen yield (142.24 mL H-2/10 mL) and rate (21.34 mL H-2/h) were obtained at this point. Model predictions and experimental results were reasonable. Blending Lemna minor with Diospyros kaki peels resulted in more efficient hydrogen production than blending with glucose.