Synergistic effect of biochar amendment in milk processing industry sludge and cattle dung during the vermiremediation

[Display omitted] •Biochar acted as an effective additive for milk industry sludge waste vermicomposting.•Addition of Biochar increased Eisenia fetida growth and reproduction.•Biochar immobilized heavy metals during the vermicomposting period.•Biochar aids in improvement of nutrients and enhanced mineralisation. The effective and sustainable management of fast growing and large quantities of industrial waste is a serious issue. The purpose of the present study was to assess the synergistic effect of biochar (BC) amended in milk processing industry sludge (MS) mixed with cattle dung (CD) in different ratios through vermiremediation. The MS25 and MS25BC10 (25:75 + 10 % BC) showed the least mortality and greatest earthworm growth and development. The final product from all feed mixtures recorded a decrease in pH, total organic carbon and C/N ratio. Other parameters viz., electrical conductivity, total available phosphorus, total Kjeldahl nitrogen, total sodium, total potassium and ash content was observed to be increased after vermicomposting. Significantly lower heavy metal content was found in all biochar amended feed mixtures than in mixtures without biochar. The germination index of Trigonella foenum-graecum showed a value ranging from 89.14 to 131.46 % for mixtures without BC and 115.18–153.47 % for biochar amended mixtures.