Anaerobic digestion can be completed at psychrophilic (10–25 °C), mesophilic (30–40 °C) or thermophilic (50–60 °C) temperatures, and can occur under hydraulic flow regimes being batch reactor (BR), sequencing batch reactor (SBR) or continuous flow reactors (CFR). Continuous flow bioreactors are operated as a plug flow reactor (PFR) or as a completely stirred tank reactor (CSTR). Both CFR types are operated at constant volume, which means that as substrate is fed into the bioreactor an equivalent volume of bioreactor content is removed at the same flow rate. Continuous flow operation requires more sophisticated equipment and is more prone to biomass washout and bioreactor failure than sequencing batch reactors. As a result, the latter is more appropriate for farm scale operations. Batch reactors consist of a tank in which 5 consecutive operations occur being: fill, react, settle, draw and idle. The organic waste is loaded into the SBR during the fill period with the length of the reaction period being sufficient to meet treatment objectives. During the settling period, no mixing is provided and quiescent conditions prevail to allow treated liquid to be separated from solids. During the draw period the treated liquid is removed, while the idle period allows coordination of simultaneous operation of two or more SBR. Methanogens grow slowly and their retention within the bioreactor is essential to its performance. In SBR, the high food to microorganism ratio (F/M) at the beginning of the feed period, and the low F/M at the end of the react period, enhance sludge settling characteristics and allow retention of a higher concentration of active microorganisms in the bioreactor (Dague et al., 1992 and Dague et al., 1998).