Abstract:
Production of biogas through anaerobic digestion of organic waste materials provides an
alternative environmentally eco-friendly renewable energy. In this study, biogas production
from co-digestion of the Justicia schimperiana and cow dung in five mix ratios,A100%JS,
B 75%JS: 25%CD, C 50%JS:50%CD, D25%JS:75%CD, E100%CD was evaluated under
mesophilic conditions (38ºC) using a batch digester in microbiology laboratory of Haramaya
University. In all treatments, Total solid, Volatile Solid, organic carbon, percent moisture
content and pH were measured before and after digestion, while, Organic carbon to Nitrogen
ratio was measured before anaerobic digestion, and found in the range of optimal nutrient
requirement for anaerobic microorganisms. The daily biogas production was subsequently
measured by water displacement method for 28 days. All measured Physico-chemical
parameters of each substrate were significantly dif erent between before and after anaerobic
digestion. Gas production was noticed in all of the substrate v a r i a t i o n from the first day
of digestion experiment and became almost zero at the 28th day in all substrates. Assessment of cumulative biogas production revealed that substrate in a mix ratio of 75% JS
and 25% CD showed the highest cumulative biogas production (924.11mL), suggesting this
mix ratio of the two substrates is an optimal mix ratio to yield better amount of biogas. Overall
results indicate that the increment of biogas yield, and VS and TS reduction can be significantly enhanced when Justicia schimperiana and Cow dung are co- digested in 3:1 ratio.i.e.75%JS:25
%CD.
