Microbial activities during mesophilic composting of manure and effect of calcium cyanamide addition

Previous study showed that manure composting would quickly reach the sanitary standard with the addition of calcium cyanamide (CaCN2). In the current study, the effect of CaCN2 addition on microbial activities was evaluated during 63 days mesophilic composting of cow manure at laboratory scale. The changes in the population of heterotrophic bacteria (eutrophic bacteria and oligotrophic bacteria), actinomycetes and various kinds of organic matter-decomposing bacteria (proteolytic, lipolytic, cellulolytic and amylolytic bacteria) were tested along the composting process. The results showed that the compostable substrates mixed with 2% and 3% CaCN2 had no significant impact on the total average populations of heterotrophic bacteria, actinomycetes, cellulolytic and amylolytic bacteria. However, addition of 2% CaCN2 significantly decreased the total average population of proteolytic bacteria while lipolytic bacteria increased in both 2% and 3% CaCN2 composting. The results revealed that addition of CaCN2, at least at the additive contents of 2% and 3% did not exert a significant inhibition on indigenous bacterial population and organic substrates degradation during the co-composting of cow manure and sawdust.