ABSTRACT The availability and usability of biodegradable waste in a locally designed engineered landfill for biogas generation was practically examined in this study. Nigeria with a population estimate of 180 million people and daily average temperature of 28oC generates waste at a minimum rate of 0.43 kg/person every day, which is disposed mostly at open dumpsites. With the availability of reliable technology like engineered landfill, sustainable energy can be harnessed from organic fraction of Municipal Solid Waste (MSW). To determine the energy potential of individual food waste, experimental design was carried out using organic feedstocks such as Beans, Rice, Yam, Fufu, Ripe Plantain, Garri, Corn, Sweet Potatoes, Ripe Banana, Pineapple and Water Melon. Preliminary tests were conducted to determine the pH and composition of soil samples from Oluku dumpsite and Uselu market dumpsite, control samples collected from a distance of 1.6 m from each dumpsite, and the control samples intermixed with food waste. Montmorillonite clay samples collected from Okada, Oduna and Okpella were subjected to geotechnical tests to determine their suitability for landfill compacted clay liner. From conceptual designs considered in this project, the landfill design prototype was constructed incorporating vertical and horizontal gas extraction pipe. Internal walls of the constructed landfill were lined with Montmorillonite clay liner and High Density Polyethylene (HDPE) liner while the drainage layer consisted of granular materials and perforated pipes to aid in the circulation of leachate. Perforated pipes were installed vertically and horizontally with gravels packed around them to allow gas ingress for evacuation. The landfill was covered with concrete slab, with manhole provided at the top for easy access, deposition and removal of organic feedstock. From the experimental design using 5 kg each of different feedstocks, Garri yielded the highest raw biogas of 140 g and highest purified biogas of 110 g. Among the aforementioned feedstocks digested, Sweet potatoes had the lowest raw biogas yield of 70 g with the lowest purified biogas yield of 50 g. The pH of soil samples from Oluku and Uselu market dumpsite were ultra-acidic (3.3 and 3.5), while pH of soil samples collected 1.6 m from Oluku and Uselu market dumpsite and intermixed with food waste were neutral in the range of 6.8-7.1 with very low chemical compositions. The clay sample from Oduna met EPA recommendation with hydraulic conductivity of 1x10-7 cm/sec, liquid limit of 50.2%, plasticity index of 31% and 50% soil particle passing through #200 sieve size. The composition of both raw and purified landfill gas collected from the system were analysed, and 55.4% CH4, 43.6% CO2 0.6% H2S, 0.2% moisture and 0.1% nitrogen were indicated in the raw landfill gas while the purified landfill gas contained 99.6% CH4, 0.2% CO2, oxygen and nitrogen in trace quantities as well as calorific value of about 30 MJ/m3 . Compared to the indiscriminate disposal of waste at open dumpsites, the adoption of engineered landfill system can yield biogas for domestic and industrial purposes in Nigeria.
