Rapidly Separating Earthworm from Vermicompost Using Two-Step Technology

Abstract

The vermicomposting has become a widely accepted approach to dispose organic solid waste such as livestock manure, plant straw and municipal sludge. With the enlargement of vermicomposting scale, it is necessary to separate earthworm from vermicompost as soon as possible before marketing. However, nowadays, separating earthworm is a bottle-neck in vermicomposting industry because it is often done manually, which is inefficient and expensive. The objective of this study is to develop a rapid and highly efficient two-step technology of separating earthworm from large-scale vermicompost. During the separation process, small granule vermicompost (diameter size < 6 mm) were separated with rolling screen and the earthworm were thoroughly separated from vermicompost through a special cone structure equipment called conical separator. Three experiments were conducted to evaluate the separation efficiency and obtain the optimal parameters for Earthworm-Vermicompost Rolling Separator (EVRS). The results showed that the optimal parameters for the EVRS were as follows: screen mesh size was 6 mm, rolling speed was 33.05 r min−1, inclined angle of rolling screen was 6.40°, screening length of rolling screen was 1290 mm and the generatrix angle of conical separator was 28°. The optimal separation effect could be achieved for EVRS at 45–55% vermicompost moisture content. Ten kg earthworm and vermicompost mixture was treated within 41.55 s, consuming electric power in 0.0025 kWh. EVRS can separate 84.38 ± 3.20% of mature earthworm and earthworm can be separated with survival rate of 96.25 ± 2.50%. In this study, the developed two-step technology and separator is a rapid, less energy consumption, highly efficient and applicable, which is expected to lighten the labor burden and shorten the recycling time of vermicomposting product.