Effect of rice husk content on thermal and chemical characteristics of rice husks and pine sawdust heterogeneous briquettes

Heterogeneous rice husk and pine sawdust briquettes present a promising alternative to meet the rising demand for household energy in Sub-Saharan Africa and other regions worldwide, while mitigating deforestation. However, their combustion performance is constrained by high ash content and low calorific value. This study aimed to formulate and characterize heterogeneous briquettes from rice husk and pine sawdust blends to identify the most efficient. Briquette analysis methods included Thermogravimetric analysis for proximate analysis; calorimetry for higher heating value (HHV); and a Water Boiling Test for thermal efficiency and emissions. Results indicated that blending biomass with compaction enhanced HHV to 16.80-18.22 MJ/kg compared to 12.8–14.5 MJ/kg for rice husk biomass alone. Briquettes with a 10% wt rice husk blend achieved the highest thermal efficiency (43.33%) and cooking power (872 W), with the lowest CO emissions (1.12 g/MJd), meeting the ISO 19867-1:2018 Tier 5 limit. The particulate matter (PM2.5) ranged from 82 to 155 mg/MJd, falling within the Tier 3 limit. These findings highlight that a 10% rice husk blend optimized performance, though efficiency remains lower than some reported biomass formulations. This practically demonstrates the potential of heterogeneous briquettes to provide cleaner household energy while reducing reliance on wood fuel. Future research should explore chemical pretreatment prior to densification to further enhance combustion efficiency, including emission performance. Future research should also incorporate economic analysis for real-world application to ensure sustainability, and structural analysis to further enhance understanding of the effects of rice husks on the combustion of rice husk and pine sawdust briquette blends. Rice husks and pine sawdust solid fuel offer clean energy and reduce deforestation. Blended rice husks and pine sawdust solid fuel burns stronger than husks alone. 10% rice husk solid fuel gave best cooking power, thermal efficiency, and emissions. Treating the mixes before pressing could make solid fuels burn more efficiently.