Available on-line at http://www.bjbabe.ro Banat s Journal of Biotechnology 2016, VII(14) 89 COMPARATIVE EVALUATION OF CUMULATIVE BIOGAS YIELD OF YELLOW YAM BRUTE CO–DIGESTED WITH COW PAUNCH MANURE IN BATCH MODE DOI: 10.7904/2068–4738–VII(14)–89 Ifeanyi Chuba Edwin UMEGHALU 1 , Josiah Chidiebere OKONKWO 2 1 Department of Agricultural and Bioresources Engineering, Nnamdi Azikiwe University, Awka, NIGERIA 2 Department of Animal Science and Technology, Faculty of Agriculture, Nnamdi Azikiwe University, Awka, NIGERIA *Corresponding author: umeghaluice@gmail.com Abstract. Anaerobic digesters were used in a study to compare cumulative biogas yield from yellow yam brute, cow paunch and yellow yam brute co–digested with cow paunch manure. It was found out that the mixture slurry of yellow yam brute mixed with cow paunch (YYB+CP) had the highest cumulative biogas yield of 668.65 mL/TMS than the cumulative biogas yield of 587.86mL/TMS and 307.96 mL/TMS obtained from the single base line substrates of cow paunch and yellow yam brute, respectively within the 35 days hydraulic retention time (HRT). It was also observed that YYB+CP and cow paunch (CP) produced almost equal quantity of cumulative biogas yield of 398.76 mL/TMS within the first 15 days of observation compared with cumulative biogas yield 178.45 mL/TMS produced by yellow yam brute (YYB) within the same HRT. It was also observed that gas production reduced seriously in mono–digested substrates YYB and Cp compared with the co–digestate because of lack of synergistic nutrients. It is generally observed that co–digestion of more than one substrate increase cumulative biogas yield. The trend of cumulative biogas yield at the end of 35 days hydraulic retention time was YYB+CP > CP > YYB. This study is aimed to evaluate the performance of biogas production from yellow yam brute mixed with cow paunch manure, and to compare its cumulative biogas yield with cow paunch and yellow yam brute digested as mono–digestate in batch mode. Keyword: Anaerobic digestion, Biogas, Substrate, Co–digestion, Cow paunch, Yellow yam brute. Introduction Globally, Nigeria is the sixth largest producer of petroleum products [NWOKOJI, 2012] , but this position has not fully solved the energy needs of the country. Presently, the country produces over 2.4 million barrels of crude oil daily with estimated crude oil reserve of over 40 billion barrels and over 176 trillion cubic feet of natural gas reserve. However, despite these huge deposits of crude oil and natural gas, the country is experiencing enormous scarcity of petroleum products especially in the rural areas where the price and supply of these products are fluctuating. A country’s economic growth and developmental aspiration is highly dependent on the cost of its energy supply sector. An investor makes maximum profit when all the economic indices point to low cost of production. Since Nigerian independence in 1960, her energy supply has been characterized with rising prices of fossil fuels, low reliability of electricity provision from national grids with persistent risk of power cuts and vulnerability of hydro power to drought [CHUKWUMA and CHUKWUMA, 2014] . Presently, power generation in the country fluctuates between 3800 and 4400 MW which has adversely affected the country’s economic growth. Effort by successive governments to break the jinx is yet to be applauded [NWOKOJI, 2012] . Bamikole stated that efforts to expand petroleum oil production by way of expanding the refineries and upgrading of the existing ones will not cut down the country’s dependence on oil, will not create the mix, will not be cheap, and will not create the employment envisioned by the year 2020 [BAMIKOLE 2012] .