Effects of stocking density and feeding rate on vermicomposting of biosolids

The double-pronged problem of quantity, and disposal of waste streams from a myriad of industries, is becoming increasingly acute, the world over. The use of earthworms as a waste treatment technique for such wastes is gainin g popularity. This method is commonly known as vermicomposting. Compared to conventional microbial composting, vermicomposting produces a product that is more or less homogenous, with desirable aesthetics, with reduced levels of contaminants and tends to hold more nutrients over a longer period, wit hout impacting the environment. Like in other related waste treatment techn iques, certain parameters need to be established for the design of efficien t and economical vermicomposting systems. Specifically, the focus of this s tudy was to investigate and establish an optimal stocking density and an op timal feeding rate for the vermicomposting of biosolids, with paper mulch p rovided as bedding. A stocking density of 1.60 kg-worms/m(2) (0.33 lb-worms /ft(2)) and a feeding rate of 1.25 kg-feed/kg-worm/ day resulted in the hig hest bioconversion of the substrate into earthworm biomass. The best vermic ompost was obtained at the same stocking density and a feeding rate of 0.75 kg-feed/kg-worm/day. (C) 1999 Elsevier Science Ltd. All rights reserved.