Sustainable Biohydrogen Production from Sucrose Supplemented with Dairy Manure

Previous studies had demonstrated the feasibility of hydrogen production from sucrose by dark fermentation under mesophilic conditions. However, the net energy gain in those studies had been negative because the hydrogen yield was not high enough to offset the heat energy input to maintain the mesophilic conditions. Because of the negative net energy gain, this route to hydrogen production is not sustainable. This study evaluated the feasibility of fermentative hydrogen production from sucrose at ambient temperature using dairy manure as a co-substrate. Batch tests were conducted at various manure:sucrose ratios to assess the practical viability of the process in terms of hydrogen yield as well as net energy gain. A kinetic model was also developed to predict hydrogen production and byproduct formation by the process. Results of this study confirmed that cattle manure could not only serve as a co-substrate, but also as a buffer to maintain optimal pH levels and as a nutrient source to provide required nutrients. Hydrogen yields found in this study with sucrose/manure blend at ambient temperatures (2.9-5.3 M hydrogen/M sucrose) are higher than those reported in the literature that had used pure sucrose at mesophilic temperatures. The net energy gain found in this study was positive and was greater than those reported in the literature. Concentrations of end products predicted by the model developed in this study agreed well with the temporal trends in the experimental data, with r² averaging 0.85 for dissolved COD; 0.94 for total COD; 0.84 for hydrogen; 0.84 for acetic acid; 0.89 for butyric acid; and 0.57 for propionic acid.