No abstract

Anaerobic digestion is an established technology to simultaneously produce biogas and treat different kinds of wastes. This work deals with water buffalo manure digested under mesophilic (37°C) and thermophilic (55°C) conditions with initial pH varying from 6.0 to 8.7. The digestion is investigated following the evolution of the biogas composition in time, in terms of the volume fraction of CH4, CO2 and their ratio. The growths of the biogas products are interpolated with a Gompertz equation and in all the investigated cases the methane productivity is above 63% with a CH4/CO2 ratio rather high and equal to about 2. In mesophilic conditions, an initial pH of 7.0 must be preferred to optimize the methane yield and to minimize the time required to attain it. The thermophilic conditions resulted very promising since they almost halved the time required to reach the final yield. The speed up of the process at 55°C, in our case, resulted to be due to the increase of the digestion kinetic more than to the selection of a new metabolic pathway.

Anaerobic digestion is an established technology to treat different kinds of wastes and to simultaneously produce biogas, a mixture of methane and carbon dioxide, which is a useful and renewable energy source. In this work, the anaerobic digestion of buffalo manure is studied. The latter is a low cost substrate rich in carbohydrates, especially suitable to produce biogas in anaerobic digesters. The process is performed both under mesophilic (37 °C) and thermophilic (55 °C) conditions with pH spanning from 6.0 to 8.7. Many different samples, deriving both from lactating and non-lactating buffaloes, are used. Under mesophilic conditions, our results are essentially in line with literature, and the highest methane concentration in the biogas (even above 65 %) is obtained with pH = 7.0. Conversely, under thermophilic conditions, we observed that also with pH > 8.0, the anaerobic process runs efficiently. In particular, methane concentration in the biogas reaches values around 70 %, with production rates almost twice those obtained at 37 °C. This experimental observation is particularly interesting for those wastes showing a natural basic pH, as the buffalo manure at hand; in these cases, in fact, the digestion process can start without any manipulation of the pH.

No abstract