Abstract:
Biogas is produced by bacteria through the bio-degradation of organic material under anaerobic
conditions. The aim of this study was to evaluate biogas production potential from anaerobic codigestion of khat (Catha edulis) and food waste with cow dung. Khat waste, food waste, and cow
dung were used for this study. Khat waste samples were collected from khat markets of Jimma
town, whereas; food and cow dung were collected from Jimma University College of Agriculture
and Veterinary Medicine. Ten treatments with different mixing proportions were conducted from
khat waste, food waste, and cow dung. These all treatments were evaluated for their potential of
gas production. The gas produced was measured by water displacement method until it stopped to
produce any more gas. The CH4 content in the biogas was determined by allowing the gas to pass
through a CO2 absorption solution. The physico-chemical parameters were determined in a
laboratory-scale bench digester for a total period of 41 days at a mean temperature of 22.5 ± 3 °C
monitored by Styrofoam. The mean, standard error of the mean for average biogas yield and
methane percentage of the triplications of the ten treatments, and correlation statistics at 5 and 1 %
significant level, respectively were carried out using SPSS software. The results in this study
indicated that the mean biogas produced in ascending order was T3 (5526 mL), T4 (5855 mL), T9
(6003 mL), T8 (6020 mL), T6 (6218 mL), T7 (6375 mL), T10 (6423 mL), T1 (6823 mL), T6
(7310 mL) and T5 (8565 mL) per 100g fresh mass sample. T5 produced the highest biogas yield.
This may be because of its optimum C/N ratio (25:1) and synergistic effects of organic matter in
terms of provision of nutrient for the growth of methanogenic bacteria. This study helps to
improve energy shortage and is a very promising way to overcome the problem of energy demand
and waste treatment of our country (Ethiopia)
