A highly cost-effective simplification in the design of fast-paced vermireactors based on epigeic earthworms

Abstract

Epigeics, such as Eudrilus eugeniae, Eisenia fetida and Perionyx excavatus are humus-feeder earthworms which, in natural environments, mostly dwell in the humus and leaf litter lying over the top soil and have very shallow borrows. In order to make the most of this characteristic of the epigeics, we have simplified the design of epigeic-based vermireactors by doing away with layers of gravel, sand and soil, normally used for maintaining the other types (anecic and endogeic) of earthworms in the vermireactors. Instead, we have laid a moistened cotton cloth at the bottom of the circular vermireaction tank and have laid the feed over it. This arrangement provides the epigeics with a thin, moisture-rich, layer of solids beneath the humus-like compost used in the reactors as feed. The bottom layer mimics the moist soil below the mulch and humus which the epigeics use for their shallow burrows in natural environments. By doing away with the conventionally used elaborate vermibed, which used to take up ∼5% of the vermireactor volume in conventional systems, we have effectively increased the utilizable fraction of the reactor volume, thereby enabling a much higher feed throughput per litre of the reactor. Six month long operation of the conventional and the modified vermireactors in two concurrently run batches – one operating at low density of E. eugeniae and the other in high-rate mode – revealed that vermicast production per litre of reactor volume in both batches of modified reactors was dramatically higher than the output in the corresponding conventional reactors.