Bioformulation of biochar as a potential inoculant carrier for sustainable agriculture

Abstract The dependence on chemical fertilizers and pesticides to increase agricultural outputs owing to the demands of a growing human population creates the need for a sustainable fertilizer. Biochar is presently a promising candidate as an inoculant carrier, given its highly porous structure, with nutrients naturally derived from the biomass, high water, and nutrient retention properties, which favor microbial growth. Biochar can be produced through pyrolysis, hydrothermal carbonization, gasification, and torrefaction. The porosity and adsorption ability of biochar allows it to be effectively used as a carrier to immobilize plant growth-promoting rhizobacteria (PGPR) for enhanced crop growth. Furthermore, the physicochemical properties of biochar like surface area, pore properties, and surface functional groups can be further modified via several activation methods, such as chemical oxidation and reduction, and physical activation to optimize the PGPR immobilization. The understanding of the agronomic impacts of biochar and the possible scaling up of cell immobilization will provide insights on the mechanism of biochar as an efficient inoculant carrier. This will contribute to fewer environmental hazards with the utilization of biochar for promoting plant growth. The complex interplay of physicochemical properties of biochar as a carrier to immobilize PGPR and the potential mechanisms of biochar-based inoculants are significant to achieve agricultural sustainability.