Torrefaction of Groundnut Shell and Straw for Improving the Fuel Quality and Bioenergy Application

Groundnut residues, specifically shells and straw, are abundant agricultural by-products in Nigeria and other developing nations. These residues are often underutilised or openly burned, contributing to environmental pollution. This study investigates torrefaction as a thermochemical pretreatment process to improve the fuel quality of groundnut residues. Groundnut shell and straw were mixed in different ratios (100:0, 75:25, 50:50, 25:75, and 0:100) and torrefied under varying temperatures (250, 270 and 2900C) and residence times (15, 30 and 60 minutes). Proximate and ultimate analyses, higher heating value (HHV), mass yield, energy yield, and energy density ratio performance were evaluated. Results showed that torrefaction reduced moisture and volatile matter content while increasing fixed carbon and HHV (up to 24 MJ/kg). Improvements were also observed in hydrophobicity, grindability, bulk density, and durability of the pellets. The findings demonstrate that torrefaction significantly upgrades groundnut residues into viable solid biofuels for domestic and industrial applications.