Morphological and chemical profiling of biochar derived from invasive aquatic weed towards bio-nanofertilizer development

Abstract

Since the early 21st century, biochar (BC) has garnered attention for its agricultural and environmental applications. Water hyacinth (WH; Eichhornia crassipes), an invasive aquatic weed, has emerged as a promising feedstock for BC production due to its rapid growth and nutrient accumulation properties. However, studies on nano-nutrient fortification of WH-derived BC and the molecular dynamics of nutrient sorption remain limited. This study prepared BC from WH leaf (D1) and stem (D2) biomasses, achieving yields of 31% and 34%, respectively, under pyrolysis at 600 °C. Furnace residence times of 15–60 minutes were evaluated, with optimal carbonization occurring at ≥30 minutes. SEM and FTIR analyses revealed highly porous structures with functional groups, including –COOH, –OH, CC, and –SO, predominantly in D1. The BC was alkaline (pH 10.7), with liming capacities of 14.76–28.94% cc_eq., zeta potentials of −34 to −38 mV, and particle sizes of 146–583 nm. The 30 minute BC exhibited high nitrogen (34 550 ppm), phosphorus (56 ppm), and potassium (609 ppm) availability, alongside water-holding capacities of 1.58–2.26 g g⁻¹. This study highlights the unexploited potential of WH as a sustainable resource towards nano-enabled biofertilizer development, offering a solution for managing the plant's invasive spread, while simultaneously improving soil nutrient management and contributing to atmospheric carbon sequestration, with positive implications for climate change mitigation.