Temperature and ph effect on methane production from buffalo manure anaerobic digestion

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.