Sequential Generation of Fermentative Hydrogen and Methane from Swine Manure with Physicochemical Characterization

Swine manure, a typical livestock waste, has great potential for biohydrogen production. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) analyses were employed to study the physicochemical characteristics of swine manure. SEM and TEM reveal that swine manure has a significantly damaged lignocellulosic matrix with cracks and debris on the surface. XRD and FTIR demonstrated that the cellulose crystallinity index of swine manure was higher than that of raw lignocellulosic biomass. A three-stage fermentation process comprising dark hydrogen, photo-hydrogen, and dark methane was performed using swine manure. Through the combined dark and photo-hydrogen production, the hydrogen yield was dramatically increased from 71.8 (dark fermentation only) to 247.7 mL of H2/g of total volatile solids (TVS). The subsequent methane yield was 87.2 mL of CH4/g of TVS using the residue of photofermentation, which increased the heat value conversion efficiency to 29.76%.