Methane Fermentation of Cowdung: Effect of Loading Rate

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Mekki, I. I
El.Amin, H. B.
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Faculty of Agriculture, University of Khartoum, Shambat, Sudan
Biogas production from cowdung was investigated on a laboratory scale using semi-continuous fermentation techniques, with loading rates of 2.5,3.5 and 4.5 g OM/L/day. A retention time of 30 days was employed for all three loading rates. The loading rate of 4.5 g OM/L/day gave the highest gas production and methane content. Increasing the load rate, generally, increased biogas production but greatly decreased the yield per unit weight. Percentage decomposition rates of organic solids were 26, 25 and 22 for the loading rates of 2.5, 3.5 and 4.5g OM/L/day, respectively. The experiment continued for 45 days (one and half turn) although the steady state was reached 30 days after the start of the process. A complete gas analysis at the steady state revealed that biogas contained an average of 65% methane, 31.9% carbon dioxide and 2.5% carbon monoxide; oxygen was not detected. Volatile fatty acids did not retard biogas production and pH level was kept automatically between 6.0 and 7.0.
Page(s): 3 (1), 119-139, 23 Ref.
retention time, gas production, decomposition, organic solids and yield.