5.4 Vermicompost and pathogen reduction

Unlike (co-)composting, pasteurizing temperatures cannot be achieved as worms and bacteria are sensitive to extreme temperatures. Instead, a combination of direct and indirect actions by the earthworms contribute to pathogen inactivation.

The direct actions include intestinal digestive action of earthworms and endosymbiotic microbes, secretion of coelomic fluids that have antibacterial activity and/or antimicrobial properties, while indirect actions are earthworm-induced growth of microbial communities, secretion of mucus, and aeration by burrowing activity.

The following schema visualizes the interaction of direct and indirect actions.

The earthworms can remove pathogens, but it is not certain that the final compost meets the pathogen reduction standard (H. Karimi, 2016). Even if the compost removal of bacteria (faecal coliform), pathogens (Salmonella spp.), and parasites (helminth ova) to acceptable safety levels can be achieved (L.G. Rodríguez-Canché, 2010), monitoring of the final product is required and hygienisation of the compost may need to follow.