Gasification Biochar from Ligno-Cellulosic Biomass: Physicochemical Characterization and Evaluation as a Soil Amendment Agent

The study aims at a systematic characterization of gasification biochar produced from a practical configuration, in contrast to pyrolysis biochar made from a controlled atmosphere. The soil-amending potential of biochar was evaluated across a wide range of dosages, with chlorophyll as a unifying, cost-effective stress indicator in plants, unlike previous circuitous parametric studies. Gasification biochar was derived from Prosopis juliflora, cashew nutshell, and coconut shell. Characterization techniques include Fourier Transform Infrared Spectroscopy, thermogravimetric analysis, ultimate analysis, nutrient profiling, heavy metals and polycyclic aromatic hydrocarbons quantification. Test soil was analyzed using standard methods, and biochar phytotoxicity was assessed in rice and radish with statistical validation. All three biochars were alkaline, carbon-rich with low hydrogen to carbon and oxygen to carbon molar ratios, heavy metals and polycyclic aromatic hydrocarbons comply with the International Biochar Initiative standards. Germination experiments showed most treatments were either non-phytotoxic or phytostimulant, even at high concentrations, whereas low dosage (1 t ha \(^\text {-1}\) ) showed moderate phytotoxicity. In radish, 55.6% of treatments were phytostimulant with a peak germination index of 188% at 10 t ha \(^\text {-1}\) for Coconut Shell biochar. In rice, 88.8% of treatments were phytostimulant with a maximum germination index of 167% at the same dosage. Strong positive correlations existed between chlorophyll and germination index (r = 0.93 and 0.69, p \(< 0.05\) ), and between post-harvested soil pH and electrical conductivity (r = 0.94 and 0.57, p \(< 0.05\) ). Gasification biochar from three different feedstocks showed high nutrient potential, strong cation exchange capacity, and phytostimulation in the majority, highlighting its inherent soil amending quality.