Second, a high ammonia concentration inhibited both
the hydrolytic and acetogenic groups of bacteria, thereby
reducing VFA concentrations in the methane fermentation
reactor. In general, the organic acid inhibition in the methane
fermentation for garbage was regarded as a serious
problem; so it was necessary to add an alkali such as
NaOH (Rao et al., 2000) or NaHCO3 (Rao and Singh,
2004) to make the pH suitable for fermentation, resulting
in a high operating cost. Therefore, in this study a cost-saving
method of adding of swine urine was proposed.