In Niger Delta (Nigeria), aside desilting and environmental pressure from crude oil pollution, agricultural encroachment like the invasive rate of water-hyacinths (Eichhornia Crassipes) and poultry litter pollution pose significant threats to lake ecosystem through ecosystem degradation and eutrophication. While mechanical and physical removal of water-hyacinths (WH) has been explored as a sustainable practice, the challenge of managing the harvested biomass remains a huge waste management issue.
Thus, this study investigates the efficacy of co-composting water hyacinth and poultry litter to improve nutrient retention and support lake restoration. A1:1 ratio blend of water-hyacinths and poultry litter, with a 10% biochar (pyrolyzed at 400c), and the same treatment without biochar was prepared as a control. The composting process was performed for 90days in 25-L plastic triangular vessels under a self-constructed greenhouse condition. Changes in Nitrogen dynamics, phosphorous release, and microbial activity were monitored.
Despite a C:N ratio of 13:1 at startup, as compared to the 30:1 and 25:1 recommended for effective composting, the results showed significant rise in temperature after 2nd day, with Control and BC-compost retaining thermophilic temperature (>45c for 12days), favoring higher microbial metabolism and pathogens destruction. Biochar enhanced NH4-N slow release, reducing volatilization losses by 18%, while promoting microbial phosphorous release and facilitated carbon sequestration. The WH biomass lignin content (7-20%) improved the compost aeration and moisture retention. While, microbes temporarily absorbed phosphorus to support their growth, reducing soluble phosphorus levels, this trend correlates with P-nitrophenol rise before 30th day, but fails to increase as P-nitrophenol decreases afterwards, indicating the influence of WH biomass richness in Calcium which fostered the formation of Ca3PO4 as a result of a pH above 8.0 during all composting stages, making it most suitable for soils of acidic to slightly neutral lakes.
This study highlights that water hyacinth and poultry litter co-composting with biochar is a cost effective, sustainable approach for invasive species control and nutrient recovery in Lake restoration. Further studies will explore its application in the bioremediation of hydrocarbon contaminated lakes.