EFFECTS OF ADDITIVES ON BIOGAS PRODUCTION FROM COW DUNG AND CHICKEN DROPPING MIXED WITH DIGITARIA SMUTS II

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Department of Engineering

ABSTRACT
This study was carried out to examine the effects of Single Super Phosphate with Wood ash on the production of biogas from Cow Dung and Chicken Droppings mixed with Digitaria Smuts II. An existing digester design was adopted (3 in 1 floating drums) and fabricated using locally available materials to digest Cow Dung from Kawo Abattoir, Chicken Droppings from Salma Farms and Digitaria Smuts II (Woolly Finger Grass) from NAPRI respectively. The study was carried out in eight (8) identical reactors to enable variation of the catalyst combination and were labelled A1, B1, C1, D1, A2 B2 C2 and D2. The research showed that using SSP and wood ash could reduce the lag phase in anaerobic digestion. The controls A1 and A2 had the longest lag phase of 7.5 and 8.9 days as compared to 5.5 and 7.9 days with (200gSSP/100gWood ash). At the end of the digestion period, there was significant difference in volume of biogas produced across the digesters which ranged from 0.0893m3 (no additives) to 0.1188m3 (200gSSP/100gwood ash) for cow dung, while that of chicken droppings mixed with grass is from 0.0647m3 (no additives) to 0.1088m3 (200gSSP/100gWood ash), indicating 20.6% and 40.6% increment respectively. The Modified Gompertz equation was applied to describe the cumulative biogas generation. The biogas production kinetic constants estimated by the linear regression method using the solver function in Microsoft Excel as well as other characteristics obtained for the eight digesters were 0.0037m3/day 0.0036m3/day 0.0045m3/day, 0.0056m3/day, 0.0025m3/day, 0.0028m3/day, 0.0031m3/day, and 0.0046m3/day for Biogas Production Rate and 0.0893m3, 0.0841m3, 0.0977m3. 0.1188m3, 0.0647m3, 0.0737m3, 0.0808m3 and 0.108 8m3 for Biogas Production Potential. The average temperatures of the digesters recorded were 35.20 0C, 35.30 0C, 35.17 0C, 35.18 0C 35.25 0C, 35.28 0C, 35.30 0C, and 35.40 0C respectively while the average ambient temperature observed during the study was 36 0C which were within the mesophilic range. The results obtain indicated that the additives used influenced biogas production.