Design and implementation of a hybrid biogas plant to reduce environmental pollution and food waste

Abstract

The Technical University of Mombasa provides hot meals for about 2,000 students a day. To achieve this, 800 kg of wood and 120 kg of LPG a month are needed. This master’s thesis focuses on two major problems: the use of fossil fuels which contributes to global warming and the management of organic food waste. To address these issues, this master’s thesis covers the design and implementation of a biogas installation. The installation processes organic waste from the kitchen in the most optimal way. This will produce biogas that will be used for cooking and digestate that will serve as a fertilizer. A literature study was conducted to arrive at the optimal fixed-dome digester. The digester combined with a floating-drum gasholder was the first version of the system. At a further stage, this installation was expanded into a hybrid system. This was done by covering the overflow tank, which eliminates the gas losses in the tank and reduces greenhouse gases. In addition, the installation was expanded with a balloon-type digester, which provides better efficiency and a more complete digestion process. To determine the volume of the gasholder, a simulation was performed. The hybrid biogas installation is expected to produce 11.88 m³ of biogas a day, which reduces the energy consumption for cooking activities by 27%. Additionally, the system is also used as a pilot plant for educational purposes. As a further development of this project, the biogas production will be measured and the quality of the biogas and digestate will be analyzed.