Optimization of Briquette Quality from Wheat Stalk and Rice Husk Residues: Physico chemical Characterization, Combustion Performance and Durability

Abstract

This study evaluated the effect of feedstock composition and pre-compression moisture on the physical, chemical and combustion properties of briquettes produced from wheat stalk and rice husk. Fifteen mixture ratios (100:0, 75:25, 50:50, 25:75, 0:100) were prepared and densified by screw extrusion at three moisture levels (8, 10 and 12% w/w). Samples were characterized by proximate analysis (moisture, ash, volatile matter, fixed carbon), higher heating value (bomb calorimeter), bulk density, durability (free-fall test) and burning rate; combustion emissions were measured with a portable gas analyzer. Statistical analysis (ANOVA, regression) was used to identify significant effects of composition and moisture. Briquettes formed at 8% moisture exhibited the highest durability and calorific performance i.e. the maximum HHV measured was 18.4 MJ·kg⁻¹ for 100% wheat stalk briquettes at 8% moisture. Durability decreased with increasing moisture (strong inverse correlation), while calorific value showed a weaker dependence on moisture. Ash content was lowest in mixes with higher rice husk fraction at the optimal moisture. The findings indicate that controlling pre compression moisture is critical to briquette quality and that wheat stalk rich briquettes produced under low moisture conditions are promising for household and small scale industrial use. The paper outlines recommendations for full reporting of densification parameters and proposes further scale up trials.