Bioconversion of water hyacinth by vermicomposting with fly ash using an exotic earthworm species Eisenia foetida

The present study aims to convert two solid wastes, Water Hyacinth and Fly Ash, into a bio-fertilizer through Vermicomposting using an exotic earthworm species i.e., Eisenia foetida. The experiments were conducted in triplicates for each treatment using varying ratios of water hyacinth (WH) and fly ash (FA): R1 (only FA), R2 (only WH), R3 (1 WH:3 FA), R4 (1 WH:1 FA), and R5 (3 WH:1 FA), over a duration of 70 days. The physico-chemical properties of the prepared vermicompost were analyzed at different time intervals using standard methods. Heavy metal concentrations in the fly ash, water hyacinth, and vermicompost were measured using ICP-MS (Agilent 7900). The findings of the study indicated that the pH of the vermicompost ranged from 6.9 to 8.5. The Total Kjeldahl Nitrogen (TKN) content was highest in R2 (9.2%) and lowest in R1, which contained only fly ash. By the end of the process, the carbon-to-nitrogen (C/N) ratio of the vermicompost was below 20 across all reactors. In terms of growth performance, Eisenia foetida exhibited the best results in R5 (3:1), where the average number and biomass of worms were the highest. The percent yield was greatest in R2 (90.65%), followed by R5, R4, R3, and R1 in descending order. The study found that the combination of 3 parts Water Hyacinth to 1 part Fly Ash (R5) has the highest C/ N ratio of 19.94, which is ideal for vermicomposting and supports the growth and reproduction of earthworms. Based on these findings, R5 is the most suitable mixture for effective vermicomposting of Water Hyacinth and Fly Ash, resulting in a valuable bio-fertilizer.