Abstract:
Biogas has been an alternative source of energy, which is generated from organic digestion under anaerobic conditions. Normally the objective was for organic waste treatment and also for an alternative source of energy. Seed culture was prepared from cow dung which contained a methanogenic microorganism. Cassava was a good carbon source, because it contained high content of starch. It is cheap and is an abundant agricultural product. When selecting varieties of cassava. Huay Bong revealed that the physical and chemical compositions of cassava were elucidated to be of 16.04% of moisture content, 70.92% of starch, 37.69% of total carbon and 0.45% of total nitrogen. Cow dung contained 81% of moisture, 13.2 mg/g of BOD, 125.5 mg/g of COD, 163.3 mg/g of total solid, 108.0 mg/g of total volatile solid, 7.80% of total carbon and 0.37% of total nitrogen. The calculated BOD to Nitrogen to Phosphorus is 100:28:4.1. The ratio of carbon to nitrogen was calculated to be 84:1 which was not suitable for biogas production. Therefore, in order to maintain the appropriated C/N ratio, urea was used as nitrogen source adding to the system. In this study, using cow dung and urea at different concentrations showed that concentrations of cow dung and urea at Suitable for biogas production was 10% and 0.08% respectively. The fermentation process was performed at room temperature (approximately 30◦C) for 30 days in 3 liters of single stage bioreactor. Changing of COD value, reducing sugar, Total carbohydrate and total gas were analysis. The suitable concentration of cassava on growth of Aspergillus awamori was also studied. The results found that concentrations of cassava were 2% w/v was the optimum concentration for growth of fungi, which could produce average biogas of 0.64 liters/day at maximum methane content of 34.8% in 26 days of fermentation at pH of 4.2-7.5. In conditions without adding A. awamori, the result revealed that the average amount of biogas was 1.03 liters/day of maximum methane concentration of 54.6% in 30 days of fermentation at pH of 7.1-8.0.