Effect of adding urea on biogas production potentials of selected fruit wastes in Addis Ababa, Ethiopia
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2012-10
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Addis Ababa University
Abstract
Fruit wastes are ideal candidates for anaerobic digestion because they contain high levels of easily biodegradable materials. These wastes from the central and biggest fruits, fish & vegetables retail and distribution market in Addis Ababa City, Ethiopia are poorly managed. Again problems such as low biogas/methane yield and process instability are often encountered in anaerobic digestion of these wastes, challenging its reliability and efficiency. This study evaluated the effect of adding urea on biogas (methane) potential of selected fruit wastes following characterization. A laboratory scale experiment on batch anaerobic mesophilic digestion was carried out. Selected and pretreated fruit wastes were fed to digesters using standard procedures. Analytical equipments, simple tools and statistical software were used for data analysis. The ultimate biogas yield from using avocado, banana, and mango fruit wastes as substrate is; 0.48, 0.57, 0.53 l/g VS without adding urea and 0.76, 0.82, 0.82 l/g VS adding urea with a statistically significant difference (p-value; 0.006 for avocado, 0.029 for banana, and 0.007 for mango FW at 95% Confidence Interval respectively). Thus urea addition significantly improved biogas yield. In relation to this, ultimate CH4 yield didn’t show difference in response to the treatment and gave 0.27, 0.33, 0.27 l/g VS without adding urea and 0.44, 0.46, 0.43 l/g VS for avocado, banana, & mango fruit wastes with adding urea where the later yield is above average yield reported for fruits and vegetables wastes. Further, the biogas manure contains nutrients in their useful form and better than the row waste for plant growth signifying the advantages of anaerobic digestion. Prediction of biogas and biogas manure obtainable from the city’s fruit wastes is also made.
Keywords: fruit waste; urea; biogas; methane; volatile acids; and plant nutrient
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fruit waste; urea; biogas; methane; volatile acids; and plant nutrient