Biowaste can be transformed into an environmentally friendly fuel, resulting in a cleaner environment. The use of plum fruit (Spondias mombin) as a substrate in a biowaste energy conversion system is a solution to the problem of fossil fuel through gasification. The aim of this research is to design and fabricate a gasifier for liquid fuel production from S. mombin (plum seed). This work was achieved by harvesting, drying, and pulverizing of plum seed after which the detailed design of the gasifier was done with the aid of solidworks. Materials were carefully selected and purchased based on availability, cost, thermal properties, mechanical properties, and their physical properties. The reactor system which consists of the reactor, pipes, and bends, shell in tube condenser, and thermocouple were fabricated. The performance evaluation of the gasifier was carried out, and various parameters such as operating time, start-up time, total operating time, fuel combustion rate, specific gasification rate, and combustion zone rate were obtained as 0.167 h, 1.17 h, 1.417 h, 11.98 kg/h, 24.94 kg/m2 h, and 4.7 (m/h) respectively. The heat load of the condenser, the logarithmic mean temperature difference (LMTD), mass flow velocity, Reynold’s number of fluid entering the condensing unit, and volume of burning chamber were also obtained as 145 kJ, 25 °C, 0.5 kg/s, 4.5448, and 0.062 m3, respectively. The maximum pressure built up in the reactor was 0.05 bar, and quantity of liquid fuel produced was 10 ml.