Optimizing Vegetable Waste-Derived Biochar: Thermal Conversion for Sustainable Soil Fertility

Abstract

Biochar is a carbon-rich material made by heating organic matter, and it can improve soil health while helping the environment. In this study, we looked at how different pyrolysis temperatures (350°C, 450°C, and 550°C) affect biochar made from onion, banana, and orange peels. We also tested how these biochars influenced soil properties and the growth of chili (Capsicum annuum) and brinjal (Solanum melongena) plants. Vegetable waste with high lignocellulose content proved to be a good source for making biochar. Our results show that the pyrolysis temperature strongly affects both the amount and chemical makeup of the biochar. Lower temperatures (350°C) gave higher yields, retained more nutrients like phosphorus (0.40% in onion peel biochar), and preserved important functional groups such as -OH and -COOH. Adding biochar to soil raised the pH and made more nutrients available. Onion peel biochar made at 350°C had a more positive effect on plant growth, producing the tallest chili (2.47 cm/week) and brinjal (2.33 cm/week) plants. These findings highlight that lower pyrolysis temperatures (350°C) provide the greatest benefit from vegetable waste biochar and support sustainable farming.