Enhancing Thermal Efficiency and Reducing Emissions in Biomass Combustion Systems for Sustainable Brick Production

• Biomass chamber reached ∼80% efficiency when using wood pellets. • Optimized air staging lowered CO emissions to about 0.33 g/min. • Refractory insulation raised thermal efficiency by up to 30%. • Efficient combustion reduced PM and CO₂ emissions measurably. • Improved biomass system outperformed conventional fossil-fired kilns. The continued use of fossil-fueled kilns in small-scale brick production results in low thermal efficiency and high pollutant emissions. Although biomass offers a renewable heat source, many existing systems are limited by inadequate air distribution and chamber design, leading to incomplete combustion. This study evaluates how targeted design improvements influence the thermal and emission performance of a small biomass combustion system. A refractory-lined cylindrical chamber incorporating staged air injection, gravity-fed fuel delivery, and multi-point monitoring was developed and tested using agricultural residues, wood pellets, and biomass briquettes. Temperature profiles, fuel consumption, thermal efficiency, and emissions of CO, CO₂, and particulate matter were measured across multiple trials and analysed in MATLAB. ANSYS Fluent simulations were used to validate the observed temperature distribution and airflow behaviour. Results show that fuel properties and chamber configuration strongly affect performance. Wood pellets achieved the highest thermal efficiency (≈80%), briquettes performed moderately (≈70%), and agricultural residues exhibited lower stability (≈55%). Design enhancements, notably improved air staging, refractory insulation, and optimised chamber geometry, collectively increased system efficiency by up to 30% compared with the baseline configuration. Emission levels decreased under optimised conditions, reflecting more complete combustion and reduced heat losses. The study provides evidence-based insights into how specific design elements contribute to improved combustion behaviour, avoiding generalised claims of superiority. Its novelty lies in integrating experimental evaluation with CFD-supported validation to isolate the functional impact of air distribution, insulation, and geometry. These findings offer practical guidance for upgrading traditional kilns and support the broader adoption of cleaner, more efficient biomass-based thermal technologies.