Effect of Temperature and Retention Time on the Quality of Biochar of Some Agricultural Waste

Abstract

The conversion of biomass and waste into valuable energy products via pyrolysis offers a sustainable solution to energy poverty and waste management challenges in Northern Nigeria. This study investigated the effects of temperature and retention time on the quality of biochar derived from three local feedstocks: groundnut shell (GS), millet husk (MH), and rice husk (RH) in Jigawa State, Nigeria. The primary objective was to determine optimal pyrolysis conditions for producing high-quality biochar. Biomass samples were pyrolyzed in a furnace at 400°C, 450°C, 500°C, and 550°C, with retention times of 30, 45, and 60 minutes. Biochar quality was evaluated through proximate analysis, ultimate analysis, calorific value measurement, and thermogravimetric analysis (TGA). Results show that higher temperatures decrease biochar yield but increase fixed carbon content. Groundnut shell char produced at 450°C achieved the highest calorific value (26.93 MJ/Kg). Millet husk char exhibited the highest carbon content (79.27%), while rice husk char had the highest ash content (39.80%). Notably, retention times exceeding 30 minutes had minimal influence on product characteristics. Overall, pyrolysis effectively converts agricultural waste into high-quality biochar. Groundnut shells and millet husk are identified as promising feedstocks for clean cooking fuel and soil amendment in rural communities..