C. S. Waswa1*, P. A. Kabok2 and D. M. Nyaanga1
1Agricultural Engineering Department, Egerton University,
P.O. Box 536 – 20115, Egerton, Kenya.
2School of Engineering, Jaramogi Oginga Odinga University,
P.O. Box 210-40601, Bondo, Kenya.
*Corresponding Author: email@example.com
Generation of biogas can greatly be influenced by feed stock pretreatment. The effect of hydro, mechanical and thermal pretreatment of chicken and goat manure on biogas production was done using a 0.15m3 laboratory scale batch digester. The feed stocks were subjected to 6, 12 and 18 hours of soaking, 2 mm, 3 mm and 4 mm of mechanical mincing, and 60˚C, 80˚C and 100˚C of heating. Pretreated feed stocks were co-digested with untreated cow manure from an extensive dairy rearing system. Experiments were done at 8 % substrate total solids and a constant temperature of 35°C. Averagely, mechanical pretreatment resulted in the highest increase in mean biogas production rate with 11.11%, over the co-digestion control (0.54 m3/m3d), followed by thermal and hydro by 5.56% and1.85%. Maximal increase in production for each pretreatment was at 6 hour soaking time (9.30%), 3 mm effective feed stock particle sizes (18.52%) and 80˚C of heating (14.81%). Co-digestion increased mean biogas production rate over mono-digestion by 68.97% (chicken), 81.84% (goat) and 8.8% (cow manure). Superior outer cell wall and cover disruption of feed stocks for easy hydrolysis advantaged mechanical pretreatment.
Keywords: Pretreatment, Chicken-goat-cow manure, Biogas production, Fixed dome, Laboratory digester