Integrating composting and vermicomposting in the treatment and bioconversion of biosolids

Traditional thermophillic composting is commonly adopted for treatment of o rganic wastes or for production of organic/natural fertilizers. A related t echnique, called vermicomposting (using earthworms to breakdown the organic wastes) is also becoming popular. These two techniques have their inherent advantages and disadvantages. The integrated approach suggested in this st udy borrows pertinent attributes from each of these two processes and combi nes them to enhance the overall process and improve the products qualities. Two approaches investigated in this study are: (1) pre-composting followed by vermicomposting, and (2) prevermicomposting followed by composting. The substrate was biosolids (activated sewage sludge) with mixed paper-mulch a s the carbon base. Eisenia fetida (red wigglers) was the species of earthwo rms used in the vermicomposting processes. The results indicate that, a sys tem that combines the two processes not only shortens stabilization time, b ut also improves the products quality. Combining the two systems resulted i n a product that was more stable: and consistent (homogenous), had less pot ential impact on the environment and for compost-vermicomposting (CV) syste m, the product met the pathogen reduction requirements. (C) 2000 Elsevier S cience Ltd. All rights reserved.