Abstract:
The unsustainability of conventional energy resources and their associated environmental pollutions made renewable energy the prime need of present time. Therefore, the research was conducted to investigate the production of biogas from Striga hermonthica co-digested with cow manure through anaerobic digestion with five treatment mix ratios were evaluated under mesophilic conditions (38ºC) using batch digesters in the Botanical laboratory of Haramaya University for 30 days of fermentation. In all treatments, physico-chemical parameters such as total solid, volatile solid, organic carbon, nitrogen, pH value and percent of moisture content were measured before and after anaerobic digestion. The results were indicated that, highest pH value (7.27 ) was observed in 10% total solid with 100% cow manure, whereas the lowest pH values (6.37) was observed in 100% Striga hermonthica with the same percentage of total solid content. Comparison of pH values between before and after anaerobic digestion showed that pH values were significantly increased after anaerobic digestion for all treatments. Similarly, maximum value of % total solid and volatile solid was recorded in 100% cow manure with 10% total solid content. In addition to this, carbon to nitrogen ratios were analyzed, the results were revealed that highest carbon to nitrogen ratio was observed in 10% total solid with 100% Striga hermonthica and lowest value in 6% total solid with mix ratio of 50% cow manure +50% Striga hermonthica. In this experimental study the result showed that co-digested substrates of the three mix ratios produced higher amount of biogas than the two sole alone. Among the different proportion of the total solid, 10%, total solid with mix ratio of 25% cow manure +75% Striga hermonthica showed the highest daily mean cumulative biogas production (2150ml) than all other treatments. Over all the results of this study indicate that the increase in biogas yield and reduction in volatile solids and total solids can be significantly enhanced when cow manure is co-digested with Striga hermonthica in 25%:75% mix ratio.
