The increased demand for energy worldwide, climate change due to emission of greenhouse gases from fossil fuel, increase in price of crude oil are the major key factors leading to need for alternative sources of energy. Biodiesel can serve as alternative to fossil fuel because it is environmentally friendly and easily renewable. This research was aimed at synthesis of biodiesel from Papaya seeds and blending it with petro-diesel to determine their potential as alternative to fossil fuel. The sample were collected, sundried, ground prior to oil extraction using Soxhlet apparatus and nhexane as solvent. The oil extracted were characterized of acid value, viscosity, SG, %FFA, %Moisture content e.t.c The oil was converted to biodiesel by acid-catalyzed esterification followed by base transesterification and properties like SG, Iodine value, Pour and Cloud point, Cetane number, Flash and Fire point were analyzed in the biodiesel. Furthermore, the biodiesel (B100) were blended with petro diesel on two different ratio i.e B20 (20% biodiesel and 80% Petrodiesel) and B50 (50% biodiesel and 50% petro diesel) and their properties were also analyzed. The % oil yield of Papaya seed was 25.40%, its Acid value was 12.20 mgKOH/g, Iodine value was 58.979mg/g. The % yield of biodiesel was 90%. The %FFA of B100, B50, B20 were 0.63%, 0.47% and 0.41% respectively. Their specific gravity were 0.902, 0.890 and 0.850 respectively; their Cetane number were 52, 50, 49 respectively, their Flash point were 1150C, 880C and 750C respectively. Most of the fuel properties of B100, B20, B50 were within the standard of ASTM D6751 and EN 14214. These showed that Papaya seed oil can serve as alternative to petro diesel
