The inhibitory effect of ammonia during anaerobic digestion of
animal wastes has been studied by several authors (10–15). Many
studies have focused on reducing the effect of ammonia inhibition
and improving the process of fermentation of CM for the production
of methane. In one of these studies, CM was diluted with water to
decrease the total percentage of solid (7, 16–18). Codigestion of CM
with other types of livestock manure, such as cattle manure (6), hog
wastes (3), and anaerobically digested sludge (ADS) (7), was also
attempted. Acclimation of methanogenic consortia to high ammonia
levels, or raising ammonia tolerance, is a proven useful method for
improving the process of anaerobic digestion and production of
methane from different kinds of wastes (10). However, only a few
studies have been conducted on CM. Demirci and Demirer (6) have
strongly recommended preacclimation in order to increase the
efficiency of the digestion process for a mixture of cattle manure
and chicken manure, but a study on CM alone has not been
reported.