Industrial & Engineering Chemistry Research, Vol.50, No.2, 639-644, 2011
Production of Gaseous Biofuels and Electricity from Cheese Whey
In this paper, the potential of energy recovery from cheese whey in the form of gas biofuels (hydrogen, methane) as well as electricity generation through application of the microbial fuel cell technology are studied. Hydrogen and methane production from cheese whey in a two-stage process has already been studied at a lab scale in a continuous stirred tank reactor (CSTR) of 3 L and a periodic anaerobic baffled reactor of 15 L, respectively. In this work, to scale up the hydrogen production step, the cheese whey fermentation process was studied at a larger scale using a 13.8 L bioreactor of CSTR type. The chemical oxygen demand concentration of the cheese whey fed to the CSTR was 53.3 +/- 3.8 g/L. The pH in the bioreactor was maintained at 5.14 +/- 0.15 with NaOH addition. The hydrogen produced reached up to 4.8 +/- 0.5 L/L/d at an hydraulic retention time of 24 h (corresponding to a yield of 1.3 mol H-2/mol consumed carbohydrates), approximately twice as much obtained in previous lab-scale experiments in a 3 L bioreactor. In addition, diluted cheese whey at different initial concentrations, was used as feedstock for electricity generation, using a two-chamber microbial fuel cell (MFC). The experiments showed that the MFC performance was not limited by the wastewater strength since the substrate removal efficiency and maximum power output were not affected by the increase of the initial concentration. The time needed for complete substrate degradation increased linearly with the wastewater strength.