A novel technology for separating live earthworm from vermicompost: Experiment, mechanism analysis, and simulation.

The vermicomposting is widely acknowledged as an effective and sustainable biological technology to dispose large scale organic solid waste such as livestock manure, crop residues and municipal sludge. The scale of vermicomposting has constantly increased over recent years due to high market demand for live earthworms. Rapid and efficient extraction and harvesting earthworm from large-scale vermicompost has become a bottle-neck problem at the end of vermicomposting. Currently, most earthworm separation is done manually or relies on simple tools, and is therefore low efficient, time consuming and labor intensive. In this study, to explore earthworm separation technology and underlying mechanisms, three major studies were conducted based on the developed separator: Earthworm separation experiment, mechanism analysis of separation, and separation process simulation. The result indicated that under a 45% moisture content of vermicompost, earthworm can be separated centrifugally with approximately 83.79% worm separation rate. The treatment capacity of separator is 21.2 kg of total vermicompost mixture per minute. The critical factor in earthworm-vermicompost separation is frictional force and liquid membrane adhesion at the contact interface of conical separator. The final separated X velocity of earthworms is higher, whereas the Y and Z velocities are less than those of vermicompost. The earthworms are centrifugally thrown to a specific area called the earthworm harvest position. The outcome of this study provides a valuable reference for improvement of earthworm harvest efficiency and for shortening the recycling period of vermicomposting products in practice.