Valorization of invasive water hyacinth into biochar for sustainable soil amendment and enhanced okra productivity

This study demonstrated the conversion of a harmful weed into value-added product, biochar. Pyrolysis of water hyacinth biomass was carried out in a semi-automated charcolator at 500 ºC (yield 36.7% ± 1.2%) and applied into the soil at three different concentrations (low, medium, and high). The biochar presented alkaline pH (8.4±0.04), moderate cation exchange capacity (1.83±0.04 meq/100g) and moderate electrical conductivity (2709±44.73 μS/cm). Fourier-transform infrared spectra indicated diverse types of functional groups (phenols, alcohols, unsaturated carbon compounds, and aromatic compounds) in Eichhornia crassipes biochar (ECB). Scanning electron microscopy and element dispersive X-ray analysis confirmed the high porosity (2.5 µm to 7.8 µm) and abundance of micro and macronutrients on biochar surface. Thermogravimetric analysis of ECB showed high thermal stability. Ameliorated soil edaphic parameters improved plant growth conditions. ECB added at medium concentration, remarkably increased shoot length and germination, and those of ECB added at high concentration recorded the highest chlorophyll content (60.5 SPAD). The experimental results showed favorable prospects for sustainable waste biomass recycling to produce valuable biochar, enhance soil health, and increase productivity of okra (Abelmoschus esculentus L.).