The inoculum should be “degassed”, i.e. pre-incubated in order to deplete the residual biodegradable organic material present in it. The pre-incubation should be done at the same temperature as the process temperature, where the inoculum was originating from. Degassing should be protracted until no significant methane production: typically 2 to 5days of incubation. In some cases, e.g. when the inoculum is taken from a reactor fed with relatively high fat/oil concentration, higher periods of pre-incubation may be required, in order to eliminate all the residual
929 I. Angelidaki et al. | Defining the biomethane potential: proposed protocol for batch assays Water Science & Technology—WST | 59.5 | 2009
(adsorbed/entrapped) substrate. The inoculum should be as closely representative as that taken from the reactor, and should not be washed to remove residual substrate material and inorganic carbon compounds as described on previous ISO 11734, ASTM E 2170 (2001).