Abstract
BackgroundComposting is one of the most environmentally friendly treatments to inactivate pathogenic organisms or reduce them to acceptable levels. However, even under thermal conditions, some pathogenic organisms such as E. coli could exist for a long time in composting. Such great persistence may increase the possibility of outbreaks of these organisms and further increase the environmental load. Calcium cyanamide (CaCN2) has recently been recognized to have the fungicidal effect on the pathogens of the soilborne diseases. So, the present study determined the effect of CaCN2 addition on composting progress as an antimicrobial agent and an amendment during forced-aeration static-pile composting of cow manure, which was mainly aimed to inhibit the pathogens that had not been inactivated by heat during composting.MethodsThe mixtures of dairy cow manure and maize straw with addition of 2 % CaCN2 or no addition were composted for 63 days. The physical, chemical and biological changes in compost mixtures were examined during composting. The data were statistically analyzed using ANOVA procedure from SAS software (version 9.0).ResultsThe results showed that the addition of CaCN2 significantly increased the maximum temperature and lengthened the duration of the thermophilic phase, and increased the percent T-N but decreased C/N ratio. For microbiological test, the addition of CaCN2 shortened the time to inactivate E. coli, and increased the total average population of thermophilic bacteria but did not significantly influence that of mesophilic bacteria.ConclusionThe results indicated that the addition of CaCN2, at least at the additive content of 2 % could benefit the thermophilic phase and the composting could quickly reach the sanitary standard during the composting of manure with maize straw in a forced-aeration static-pile system. This finding will contribute to solve the feces disposal problems.
Highlights
Composting is one of the most environmentally friendly treatments to inactivate pathogenic organisms or reduce them to acceptable levels
The survival of the pathogens is greatly different in different systems, for example, in some composting systems even under thermal conditions, some strains of pathogens could exist for a long time or recover after some days
Others reported that lower temperatures were still efficient to inactivate bacterial populations such as E. coli, the temperatures included 45 °C for 72 h in a study conducted by Lung et al [19] and 33.5 to 41.5 °C for 7 days by Larney et al [20]
Summary
Composting is one of the most environmentally friendly treatments to inactivate pathogenic organisms or reduce them to acceptable levels. Even under thermal conditions, some pathogenic organisms such as E. coli could exist for a long time in composting. Such great persistence may increase the possibility of outbreaks of these organisms and further increase the environmental load. Composting is the most efficient process to produce an agronomically advantageous soil organic amendment, and one of the most environmentally friendly treatments to inactivate pathogenic organisms or reduce them to acceptable levels [4, 5]. The survival of the pathogens is greatly different in different systems, for example, in some composting systems even under thermal conditions, some strains of pathogens could exist for a long time or recover after some days.
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