Determination of optimal mixing ratios of different feedstock for optimal Biogas production in Uganda.

Abstract

Biogas is a type of biofuel that is naturally produced from the anaerobic decomposition of organic waste, composed of mostly methane and carbon dioxide though other trace elements may be formed are the major constituents. When organic matter, such as food scraps and animal waste, break down in an anaerobic environment they release a blend of gases, primarily methane and carbon dioxide. Anaerobic digestion is a natural form of waste-to-energy that uses the process of fermentation to breakdown organic matter. Biogas is a clean- burning “green” gas used for heating, cooking, transport, and power generation. Dissemination of biogas energy is constrained by inadequate preparation of feedstock, few number of locally trained technicians, poor workmanship and competition from other energy sources. The study was carried out by carrying out prefeasibility study in districts of Kampala, Mbarara, Isingiro, Mityana and Wakiso to assess the performance of possible digesters and the challenges biogas users face. This study investigated the digestion of cow dung, pig dung and chicken waste for biogas production at laboratory scale with an aim to establish optimal conditions for digestion of the mentioned feedstock. The laboratory study was carried out by mixing together different ratios of cow dung, pig dung and chicken waste under mesophilic conditions (temperature between 27-350 c) and a pH of (6.2 to 6.8) for 30 days. The biogas obtained from the experiment was analyzed using a biogas analyzer to test its quality by getting the percentage composition of the constituents from the samples. The results from the experiment show that 25% pig dung and 75% cow dung gives the optimal mixing ratio for optimal biogas production in Uganda. It was also proved that investment in biogas technology is a viable venture basing on the fact that it has a shorter payback period (PBP) and a positive Net Present Value (NPV) and since optimal biogas production indicates large volume of biogas production in a given time, further gas cleaning and upgrading to improve its quality as well as increasing the heating value makes this gas an efficient and cost effective source of energy for engines, boilers, vehicles, and power generation.