THE EFFICIENCY OF BIOGAS PRODUCTION FROM CO-DIGESTION OF Gossypium barbadense L. LEAVES WITH COW DUNG THROUGH ANAEROBIC FERMENTATION

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.