Effects of a precomposting step on the vermicomposting of dairy manure-waste paper mixtures

Thermophilic composting is being promoted as a means of sanitizing waste materials prior to vermicomposting. The precomposting duration is, however, critical to the success of the vermicomposting phase as it affects worm biomass. This study evaluated the effectiveness of different precomposting periods (0, 1, 2, 3 and 4 weeks) on the sanitization and vermicomposting of dairy manure-waste paper mixtures. The parameters measured were coliform bacteria and protozoa oocyst numbers, earthworm growth, as well as stabilization and nutrient content of vermicomposts. Over 95% of fecal coliforms, Escherichia coli and of E. coli 0157 were eliminated from the waste materials within 1 week of precomposting and total elimination of these and protozoan oocysts was achieved after 3 weeks of precomposting. Microbial biomass carbon and water soluble carbon of waste mixtures decreased with increase in precomposting time and impacted negatively on earthworm growth and subsequent stabilization of the dairy manure-paper waste mixtures. Vermicomposts from waste mixtures precomposted for over 2 weeks were less stabilized, less humified and had lower nutrient contents than vermicomposts from waste mixtures precomposted for 1 week or less. A precomposting period of 1 week was found to be ideal for the effective vermicomposting of dairy manure-waste paper mixtures.