Vermicomposting of grass and newspaper waste mixed with cow dung using Eisenia fetida: physicochemical changes

This study was conducted to investigate the effect of different types of organic wastes (grass and newspaper wastes, cow dung and their combination) on physicochemical properties during vermicomposting using Eisenia fetida. Three set-ups were conducted in which three experiments were for composting (controls) indicated as C1 for newspaper waste, C2 for grass waste and C3 for cattle dung and the corresponding replicates for vermicomposting processes for grass and cattle dung were T1 to T7 and mixed of newspaper, grass and cattle dung were T8-T13. A significant difference was detected among weight and number of Eisenia fetida in treatments, which the highest weight and population growth of worms occurred in T7 (60% of newspaper, 30% of cattle dung and 10% of grass waste). Compared to control treatment (without earthworms), vermicomposting treatment resulted in a decrease of organic carbon and C/N ratio after 30 days. Vermicomposting caused significant reduction in organic carbon (3.9-32.8% ) and C/N ratio (7.9–33.6%). The heavy metals degradation was evaluated after 90 days and at the end of the experiment the concentration of As, and Cd significantly decreased. This study clearly indicates that vermicomposting is a suitable technology for bioconversion of newspaper waste, grass clipping and cow dung to valuable material.