Vermicomposting of sludges from paper mill and dairy industries with Eisenia andrei: A pilot-scale study

We studied vermicomposting with Eisenia andrei of sludges from a paper mill mixed with cattle manure in a six-month pilot-scale experiment. Initially, a small-scale laboratory experiment was carried out to determine the growth and reproduction rates of earthworms in the different substrates tested. In the pilot-scale experiment, the number of earthworms increased between 22- and 36-fold and total biomass increased between 2•2- and 3•9-fold. The vermicomposts were rich in nitrogen and phosphorus and had good structure, low levels of heavy metals, low conductivity, high humic acid contents and good stability and maturity. These sludges could be potentially useful raw substrates in larger commercial vermicomposting systems, and would reduce the costs related with the exclusive use of different types of farm wastes as feed for earthworms.