Abstract:
Biogas generation and its utility as an alternative renewable energy source are gaining
attention, particularly among developing countries. In this study, biogas production was
evaluated from Gosspium barbadense leaves (GB) and cow dung (CD) co-digestion in five
mixed ratios (A =100% GB, B=25 % GB+75% CD, C=50%GB+50%CD, D=75
%GB+25%CD, E= 100% CD.) under mesophilic conditions using batch digesters. The daily
biogas production was subsequently measured by the water displacement method. In all
treatments, physico-chemical parameters such as total solid , volatile, organic carbon, total
nitrogen , carbon to nitrogen ratios and pH, were measured and before and after AD .The
results also indicated that after anaerobic digestion, 100% GB was the lowest pH value, at the
same time, the highest value pH was noticed in 100% CD. The moisture content of 100% GB,
25% GB+75% CD, 50% GB+50% CD, 75GB% +25%CD and 100% CD before AD were
5.367 ± 0.28%, 6.600 ± 0.47 %, 6.700 ± 0.63%, 6.833 ± 0.29%, and 7.200 ± 0.43%,
respectively. This result showed that the % of organic carbon of the substrates in the digester
increases with the increasing in the CD content and a simultaneous decrease in the GB content
of the mix ratios. Moreover, the highest % of total nitrogen was observed at 100% CD,
whereas the lowest % of total nitrogen was shown at 100% GB. In this study, the maximum
reduction (18.03%) of TS was recorded in treatment D (75%GB+25%CD), whereas the
minimum reduction (8.52%) of TS was reduced in treatment E (100%CD). Before AD , carbon
to nitrogen ratios (C:N) of all treatment were found in the recommended range 20:1 to
30:1, which was a suitable condition for methanogenic bacteria to reproduce and
produce optimum biogas. The highest daily mean biogas was obtained in treatment D, which
is 576.7 ml, followed by treatment C, which is 447.7 ml. The evaluation of biogas yield
revealed that the highest cumulative biogas production was recorded in the mix ratios of
75% GB and 25%CD treatment ,suggesting that the substrates ratio is an optimum mixed
ratio to enhance biogas production.
