Performance evaluation and Exergetic analysis of a pilot-scale vertical biodigester using cow dung
Department of Mechanical Engineering, University of Ibadan, Ibadan, Oyo State.
Research Article
International Journal of Frontiers in Engineering and Technology Research, 2026, 10(02), 001–013.
Article DOI: 10.53294/ijfetr.2026.10.2.0015
Publication history:
Received on 17 March 2026; revised on 25 April 2026; accepted on 29 April 2026
Abstract:
Fossil fuels dominate global energy consumption, necessitating the shift to sustainable alternatives like biogas. This study investigates the thermodynamic and economic feasibility of cow dung-based biogas as a small-scale cooking fuel in a Nigerian context. Biogas was produced using cow dung feedstock in a locally fabricated 0.165m3 vertical drum reactor operated in a semi-continuous mode. Gas composition was measured using the wet chemistry method, followed by a boiling test for heat value determination and a second-law (exergy) analysis to assess thermodynamic efficiency. Finally, a breakeven analysis compared biogas viability against common household fuels, kerosene, and Liquefied Petroleum Gas (LPG). The biogas contained 70% methane, yielding a heating value of 25,098 kJ/m3, indicating high methane quality typical of well- digested slurry. However, the second-law efficiency was only 4.87%, reflecting significant exergy losses primarily due to burner inefficiencies. The breakeven analysis demonstrated that the biodigester investment becomes cost-effective after approximately 337 nominal days when replacing LPG, and 525 nominal days when replacing kerosene. These findings confirm the strong potential of cow dung biogas as an environmentally friendly and economically viable long-term energy source. Improved burner efficiency is critical to maximising the thermodynamic potential and speeding up the adoption of this technology.
Keywords:
Biogas; Cow Dung; Cooking Fuel; Economic Feasibility; Exergy
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