Vermicomposting of paper industry sludge with cowdung and green manure plants using Eisenia fetida: A viable option for cleaner and enriched vermicompost production

Vermicomposting of paper mill sludge (PMS) with cowdung (CD) and green manure plants, Tephrosia purpurea (TEP) and Gliricidia sepium (GLS) in different combinations (21 days pre-decomposed) was carried out using Eisenia fetida (60 days). Results revealed that electrical conductivity, total Kjeldahl nitrogen, total phosphorus, total potassium and N-NO3- levels were higher in vermicomposts generated from PMS + CD with TEP/GLS combination than in composts prepared without earthworms; while total organic carbon, C/N ratio, C/P ratio and organic matter content depicted significant reduction. C/N and C/P of final vermicompost ranged from 13.45 to 22.33 and 15.54 to 28.56 respectively. The total microbial population was significantly higher in CD + TEP/GLS vermicomposts (P < 0.001). Activities of dehydrogenase, urease, acid and alkaline phosphatases during vermicomposting elevated initially and then declined, indicating vermicompost maturity. Also, the seed germination tests with maize and cowpea in vermicomposts of PMS, CD and green manure combination support the maturity and less phytotoxic nature of vermicompost produced. Growth and reproduction of E. fetida explained that the addition of CD along with GLS/TEP significantly created an impact on bioconversion of PMS. The PMS + CD + TEP/GLS (2:1:1 ratio) combination can be used for sustainable PMS utilization through vermicomposting, and enriched vermicompost can also be obtained by the addition of green manure plants. (C) 2019 Elsevier Ltd. All rights reserved.