Dark fermentative hydrogen production from hydrolyzed sugar beet pulp improved by nitrogen and phosphorus supplementation.

The effect of nitrogen and phosphorous addition on hydrogen production from hydrolyzed Sugar beet pulp (SBP) was investigated using (NH4)3PO4, NH4Cl and K3PO4 as the supplements. In batch tests, the maximal hydrogen production of 279 dm3/kgVS was observed for K3PO4, which was added to SBP in a dose of 1 g/dm3. In semi-continuous experiments, the greatest hydrogen production of 36 dm3/kgVS was reported for the same supplement, and this value was twice higher than that of the control run. The analysis of microbiota revealed that the majority of bacteria was affiliated to the orders Clostridiales, Lactobacillales and Coriobacteriales. Moreover, a noticeable methane production was associated with the activity of Methanosphaera sp., which could grow in a low pH environment of dark fermentation.

Dark fermentative hydrogen production from hydrolyzed sugar beet pulp improved by iron addition.

This study evaluated the impact of three different iron compounds (Fe2O3, FeSO4, FeCl3) on hydrogen production via mesophilic dark fermentation (DF) of hydrolyzed sugar beet pulp (SBP). In batch tests, the maximum hydrogen yield of over 200 dm3H2/kgVS was achieved with the addition of 0.1 gFe2O3/dm3, which was twice greater than the control. In semi-continuous experiments, the highest hydrogen production of 52.11 dm3H2/kgVS combined with 19.4 dm3CH4/kgVS methane yield was obtained at a dose of 1 gFe2O3/dm3. Acetic, lactic and caproic acids were the main metabolic products of DF. Microbiological studies showed some balance between hydrogen producing microorganisms from the order Clostridiales and lactic acid producers (LAB) affiliated with the orders Lactobacillales and Coriobacteriales. Moreover, the presence of methanogens affiliated to the genera Methanobrevibacter and Methanosphaera was also documented. An interesting finding was the appearance of rare bacteria from the genus Caproiciproducens, which was responsible for increased caproic acid production.