The purpose of this research was to study the physical and economic characteristics of carbonized briquettes from rain tree (Samanea saman) residues and coffee ground/tea waste with cassava starch (10% wt.). This experiment utilized five treatments. As a binder, 10% wt. cassava starch was added to five ratios of rain tree residues to coffee ground/tea waste: RT100:CT0, RT75:CT25, RT50:CT50, RT25:CT75, and RT0:CT100. The physical properties of the carbonized briquettes were analyzed using ASTM methods. The results showed that carbonized briquettes made from 50% rain tree (Samanea saman) residues and 50% coffee ground/tea waste (RT50:CT50) had the highest calorific value (20.17 ± 0.042 MJ/kg)-insignificant at the 95% confidence interval-and highest shatter index (99.16 ± 0.20%). However, all ratios of rain tree residues to coffee ground/tea waste can produce carbonized briquettes for household use, convenient for transportation. In terms of economic performance, carbonized briquettes made from 50% rain tree (Samanea saman) residues and 50% coffee ground/tea waste (RT50:CT50) achieved the optimal payback period (approximately six months). Thus, making carbonized briquettes from rain tree residues and coffee ground/tea waste a viable alternative method of adding value to biomass residue for use as raw materials to produce fuel products for household cooking.

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