Effect of Thermal and Mechanical pre-Treatments on the CH₄-H₂ Production from Water Buffalo Manure in Different Process Conditions

Abstract

Animal manure can be profitably used to produce energy in anaerobic fermenters increasing energy independence and reducing disposal costs and pollution. Animal manure is a low cost substrate rich in carbohydrates, especially suitable for biofuels production, such as hydrogen and methane. We preliminary studied the effect of mechanical manure pre-treatments on the fermentation process focusing on the biogas yield and composition. In particular, we investigated both the H2 and CH4 oriented fermentation. Our batch reactors consist in 280 ml serum glass bottles hermetically sealed with pierceable rubber cups. The products of fermentation were measured with a micro gas chromatograph, equipped with two capillary columns. To individuate the most suitable conditions for H2 production, a manure thermal pre-treatment, used to isolate the H2-producing bacteria, was investigated. Preliminary results show that the mechanical pre-treatments do not systematically alter the fermentation process. Concerning the thermal pre-treatment, we found that the CH4 production is inhibited when the manure is heated at the 90 °C for several hours. Moreover, we identified the most favorable conditions to optimize the production of H2: i) thermal pre-treatment on the substrate; ii) initial pH ~ 5.0; iii) process temperature of 55 °C. The favorable conditions to optimize the production of CH4 are: i) initial pH ~ 7.0;ii) process temperature of 37 °C.