Evaluation of biogas production rate and biochemical changes in pig dung used in a simple mobile bio-digester

Abstract

The rate of biogas generation and biochemical changes in pig dung used in a simple mobile biogas digester designed and constructed at the Department of Environmental Technology, Federal University of Technology Owerri, Nigeria were evaluated. Measurable gas production started 4 days after feeding the digester with pig dung with daily gas volume at this point standing at 0.005m³ and stabilizing at 0.035m 3 for the 5 th and 6 th day. Thereafter, daily gas production dropped and was fluctuating between 0.001m³ and 0.002m³ from the 7^th to the 22^nd day, and then rose to 0.003m³ on the 23^rd day and maintained a daily production volume of 0.009m³ from the 24^th to 27^th day. A constant volume of 0.008m³ produced for the next 5 days. From the 33^rd day the daily gas volume began to increase exponentially to an optimum volume of 0.070m³ on the 42^nd day after feeding the digester. All biochemical parameters of the dung analyzed such as Moisture (%), Ether Extract (%), Ash (%), Crude Protein (%), Crude Fiber (%), Crude Fiber (%), Nitrogen (%), Phosphorous mg/100gm and Potassium mg/100mg, showed significant decreases in values after 37 days of digestion except crude fiber value which increased significantly (p<0.05). These results indicate that it takes up to 3 weeks before utilizable gas could be produce by a digester of this type. The maximum 0.07m³ of biogas produced and estimated to equal about 0.5 liter of gasoline was relatively small and was attributed to the small size of the digester.

Keywords: pig dung, mobile bio-digester, biogas, biochemical changes

Animal Production Research Advances Vol. 1(1) 2005: 32-38