STEAM EXPLOSION PRETREATMENT FOR ENHANCING BIOGAS PRODUCTION OF GROUNDNUT SHELL AND COWDUNG

Abstract

The demand, high costs and health implications of using energy derived from hydrocarbon compound have necessitated the continuous search for alternative source of energy. Groundnut shell (GS) and Cow dung (CD) as renewable source of energy supply have been proven to be very efficient. This study investigated the production of biogas using steam explosion (SE) of GS and CD. Ten (10) plastic digester of size 4,000cm3 was constructed, the digester were labelled A to J. The result of chemical analyses shows that SE reduces the total solid of GS from 87.90% to 79.42% while the volatile solid was increased from75.11% to 86.32% as a result of SE pre treatment. Though the nitrogen content of GS increases after SE the carbon content remain barely constant even after SE. Lignocelluloses content of the substrate are: Hemicellulose before and after pre-treatment are 34.11% and 40.20% respectively, Cellulose are 30.50% and 28.80% while lignin before and after pre-treatment are 35.39% 31.00% respectively. Hemicellulose consists of several type of sugar unit and sometimes referred to by sugars they contain. Digester A been the control containing 100% of CD have pH of 7.00 and 7.20 before and after digestion respectively. This shows that the pH values of CD was neutral before digestion and slightly alkaline after digestion while digester E containing 100% of GS also a control have pH of 7.10 and 7.20 respectively before and after digestion. There was fluctuation in the quantity of gas produced from each substrate possibly due to variation in the ratio of the substrates. The co-digestion of 25%CD-75%GS, 50%CD-50%GS, and 75%CD-25%GS have their highest gas production around sixteen and twenty-first day of retention period respectively while their least were also recorded toward the end of the retention period. Also, digester A and E containing 100% each of CD and GS have their highest biogas production around eighteen and twenty first day of retention period respectively and the least is also seen in toward the end of the digestion. Also, from the results it was observed that digester A and F containing 100%CD each produced the highest biogas and this could be attributed to multiplication of microbial organism within the methanogenesis stage, the digester E and J containing 100% each of GS digested alone produce the least biogas. So, pre-treatment of GS before digestion enhance gas production. Thus biogas production from CD is a good and cheap alternative source of energy