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Abstract
The experimental works of this study were carried out in biogas laboratory, Agric. Eng.
Dep., Fac. of Agric., Suez Canal Univ., Ismailia, Egypt. The present work aimed to study
the effect of substrate type (100% cattle dung (CD), 100%chicken manure (CM) as monodigestion
and amixture of themas co-digestion (CD+CM, 1:1 byweight) at TS 7.75%) and
digester shape (horizontal and vertical) on quantity and qualityof biogas produced at various
digestion temperatures of 20±3 (at winter), 29±3 (at summer) and 38±1 ºC (controlled
temperature) and a digestion period of 60 days.
The cumulative biogas or methane productions were found increase with increasing
digestion time reaching their highest amounts at the end of experiments. Highly significant
linearly correlations were observed. The horizontal digesters produced considerably high
amounts of cumulative biogas or methane than the vertical ones.
In all treatments of the three experiments, the cumulative and daily specific biogas and
methane production followed the order: CD+CM > CD > CM, except for the vertical
digesters at 38±1 ºC followed the order: CD+CM > CM > CD. This result demonstrated
that, the co-digestion of CM with CD was more effective than the digestion with each of
themalone.
The highest average methane content of 68.1% (by volume) in biogas was observed in
the vertical digesters fed with CD+CM at digestion temperature of 29±3 ºC. On the
contrary, the lowest average methane content of 42.0%was found in the horizontal digesters
loaded with CMalone at 38±1 ºC.
The highest average specific biogas and methane production rates of 355 and
238 L kg-1VS added per day, respectively, were obtained from the horizontal digesters fed
with CD+CMat 29±3 ºC, while the lowest rates of 79 and 32 L kg-1VS added per day were
observed in the horizontal digesters loaded with CMalone at 38±1 ºC, respectively.
This study demonstrated that the utilization of a mixture of CD+CM (1:1 by weight)
with 7.75% TS as a substrate in the horizontal biogas digesters at ambient digestion
temperature of 29±3 ºC and digestion time of 60 days gave the highest quantity and quality
of biogas compared to all other treatments of the three. These results are recommended to
apply on field-scale digesters.