Hydrogen and Methane Production, Energy Recovery, and Organic Matter Removal from Effluents in a Two-Stage Fermentative Process

This study evaluates the potential for using different effluents for simultaneous H 2 and CH 4 production in a two-stage batch fermentation process with mixed microflora. An appreciable amount of H 2 was produced from parboiled rice wastewater (23.9 mL g −1 chemical oxygen demand [COD]) and vinasse (20.8 mL g −1 COD), while other effluents supported CH 4 generation. The amount of CH 4 produced was minimum for sewage (46.3 mL g −1 COD), followed by parboiled rice wastewater (115.5 mL g −1 COD) and glycerol (180.1 mL g −1 COD). The maximum amount of CH 4 was observed for vinasse (255.4 mL g −1 COD). The total energy recovery from vinasse (10.4 kJ g −1 COD) corresponded to the maximum COD reduction (74.7 %), followed by glycerol (70.38 %, 7.20 kJ g −1 COD), parboiled rice wastewater (63.91 %, 4.92 kJ g −1 COD), and sewage (51.11 %, 1.85 kJ g −1 COD). The relatively high performance of vinasse in such comparisons could be attributed to the elevated concentrations of macronutrients contained in raw vinasse. The observations are based on kinetic parameters of H 2 and CH 4 production and global energy recovery of the process. These observations collectively suggest that organic-rich effluents can be deployed for energy recovery with sequential generation of H 2 and CH 4 .