5. Summary and conclusion
The design and functioning of a novel vermicomposting machine, acronymed
HEVSTOW (High Efficiency Vertically Stacked vermicomposting system for
Treating Organic Waste), on which a patent has recently been granted, is
described. Over 6-month long uninterrupted operation HEVSTOW was able to
simultaneously vermicompost different substrates with different species
of earthworms. It functioned to its designed capability and efficiency
throughout. By following the paradigm of high-rate vermicomposting,
developed earlier by the authors, it was possible to directly
vermicompost in HEVSTOW the weed water hyacinth (Eichhornia
crassipes) without pre-composting it or doing any other form of
pre-treatment. The machine was also able to vermicompost paper waste ─
which had been pre-soaked in water containing 10% (w/v) of fresh
cow-dung ─ as swiftly as it processed water hyacinth. It was possible to
achieve convertion of all the substrate to vermicompost within a solid
retention time of just 20 days. The vertically stacked multi-module
design of HEVSTOW was thus seen to enable unprecedentedly high
efficiency of vermicomposting in terms of space as well as time.