Coal remains a primary energy source, widely used for fuel and electricity generation, but it is also a major contributor to global carbon emissions, responsible for over 40% of the 15.3 billion tons of CO₂ emitted in 2021. In response, researchers are exploring strategies to reduce coal usage in briquette production. One promising alternative is biomass-based briquettes, designed to offer comparable performance to traditional charcoal while being more sustainable. This study investigates the thermal and mechanical properties of briquettes made from rice husk (RH) and coffee husk (CH), focusing on how particle size affects their heating value. RH and CH are rich in lignin, cellulose, and hemicellulose, crucial for briquette structure, while tapioca flour, used as a binder, provides amylose and amylopectin to enhance bonding. The carbonization process was conducted at 400°C for 60 minutes. Researchers used a 25% CH to 75% RH blend and evaluated three mesh sizes (60, 80, and 100). Briquettes were assessed based on calorific value, moisture content, shatter index, volatile matter, fixed carbon, density, ash content, and combustion rate. The results showed that the 100-mesh sample had the highest density, moisture content, volatile matter content, and burning rate with the value of 662.81 Kg/m3, 6.7%, and 7.07%, respectively. In contrast, the 60-mesh sample had the highest ash content (5.01%), as well as the lowest fixed carbon (82.04%) and shatter index (4.36%). These findings indicate that mesh size significantly affects the thermal and mechanical properties of the briquettes.