<![CDATA[This study aimed to develop a heterogeneous base catalyst derived from Cyperus rotundus biomass and to evaluate its application in biodiesel production from palm oil. The catalyst was prepared through a series of processes, including washing, drying, grinding, and calcination at 600 °C for 2 h. The prepared catalyst was then characterized using X-ray fluorescence (XRF), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) analysis, and the Hammett indicator method. The transesterification reaction was carried out at 60 °C for 30 min, with variations in the methanol-to-oil molar ratio (9:1–21:1) and catalyst loading (3–11 wt%). The characterization results revealed that the catalyst contained a high proportion of K₂O (44.5%), had a specific surface area of 89.821 m²/g, and exhibited a basicity of 0.5 mmol/g. The biodiesel yield increased with increasing methanol-to-oil molar ratio and catalyst loading until the optimum conditions were reached, after which the yield decreased due to mass transfer limitations and difficulties in glycerol separation. The highest biodiesel yield of 96.31% was obtained at a methanol-to-oil molar ratio of 15:1 and a catalyst loading of 7 wt%. The resulting biodiesel had a density of 0.8809 g/cm³, a kinematic viscosity of 3.0691 mm²/s, an acid value of 0.3366 mg KOH/g, and a flash point of 235 °C. These properties met the requirements of the SNI 7182:2015 standard. GC-MS analysis identified methyl oleate and methyl palmitate as the major components of the biodiesel. Overall, the results demonstrate that Cyperus rotundus biomass has potential as an environmentally friendly source of heterogeneous base catalysts for biodiesel production.]]>
