Vermicomposting of tannery sludge mixed with cattle dung into valuable manure using earthworm Eisenia fetida (Savigny)

► Study revealed the role of earthworm in converting tannery sludge into a valuable product. ► Number of worms, cocoons and hatchlings were taken as indicators of the suitability of feed mixtures for earthworms. ► Nitrogen, sodium, phosphorus and pH increased in the products of vermicomposting. ► Organic carbon, potassium and electrical conductivity decreased in the final products. ► Transition metals increased from the initial value and within the permissible limit.