Cleaner cooking solutions: Optimizing biomass briquettes to replace charcoal and mitigate climate change in Tanzania

• Coconut shell, palm kernel shell, and charcoal dust showed high carbon (>65%), low ash (<10%), and high calorific values (6,299–6,737 kcal/kg). • Starch-based briquettes had highest strength (>93%), rapid ignition (2–4 min), and steady burning (4–8 g/min). • Blending rice husk with biochar (60:40) improved calorific value (4,741–5,552 kcal/kg), reduced ash (<20%), and enhanced durability. • Optimal starch loading: 20% for single-feedstock, 25% for blends, balancing energy and strength. • The study offers a scalable approach for sustainable biomass briquettes in sub-Saharan Africa. This study investigated the optimization of biomass briquettes produced from locally available agricultural residues (coconut shell, palm kernel shell, rice husk) and forest wastes as sustainable alternatives to charcoal in Tanzania. Carbonized feedstocks were blended with starch, molasses, or clay binders at varying ratios, and their proximate, energy, combustion, and mechanical properties were examined. The results demonstrated that feedstock type strongly influenced briquette performance, with coconut shell, palm kernel shell, and charcoal dust exhibiting high fixed carbon (>65%), low ash (<10%), and superior calorific values (6,299–6,737 kcal/kg). Among the binders, starch produced the best overall results, yielding briquettes with high shatter resistance (>93%), rapid ignition (2–4 min), and steady burning rates (4–8 g/min). Molasses produced moderately strong briquettes with acceptable energy output but slightly higher ash content, while clay enhanced shape retention but reduced calorific value and prolonged ignition due to its non-combustible nature. The optimal starch loading was 20% for single-feedstock briquettes and 25% for blended systems. Blending rice husk with high-energy biochar at a 60:40 ratio improved calorific value (4,741–5,552 kcal/kg), reduced ash content (<20%), and enhanced mechanical durability, converting low-grade residues into efficient solid fuels. The optimal starch loading was 20% for single-feedstock briquettes and 25% for blended systems. Blending rice husk with high-energy biochar at a 60:40 ratio improved calorific value (4,741–5,552 kcal/kg), reduced ash content (<20%), and enhanced mechanical durability, whereas the 50:50 blend exhibited moderate performance with lower energy density and higher ash levels, converting low-grade residues (rice husks) into efficient solid fuels. This research advances practical knowledge on optimizing feedstock blending and binder formulation to enhance biomass fuel quality, offering a scalable model for sustainable energy transitions in sub-Saharan Africa.