Journal Of Tropical Biosciences
Volume No: 11|
Page No: 9
| FullText PDF
EVALUATION OF COW DUNG AND RICE HUSK WASTES SUBSTRATES FOR BIOGAS PRODUCTION USING LOCALLY FABRICATED DIGESTERS
ASIRU, R.A.*; ADO, S.A. AND MACHIDO, D.A.
DEPARTMENT OF MICROBIOLOGY, AHMADU BELLO UNIVERSITY, ZARIA, NIGERIA
Biogas production from organic wastes is a sustainable waste management strategy that produces an agriculturally valuable sludge, as well as biogas. The study was conducted to assess the potentials of cow dung and rice husk as substrates for biogas generation at laboratory scale. The study was carried out at mesophilic condition between (37- 40)°C and natural pH of the slurry for a period of 30 days. The total biogas produced during digestion was estimated by water displacement method. When substrates digested individually at mesophilic temperature, cow dung yielded the highest volume of biogas (581cm3), followed by rice husk (8cm3). Combining the two substrates in 1:1 proved more productive in term of biogas yield, however there were no significant differences (p<0.05) between the biogas produced by cow dung (581cm3) alone and the combination of the substrates (715cm3). The quality of biogas produced was evaluated by flame test. Seven bacteria species were isolated from the slurry in the digesters during various stages of anaerobic digestion and confirmed by standard bacteriological identification procedure. The bacteria species identified are; Peptococcus spp, Peptostreptococcus spp, Clostridium baratii, Clostridium sporogenes, Methanobacterium formicicum, Methanobacterium oryzae and Methanosarcinafrisia. It was concluded that co-digestion of rice husk and cow dung increased biogas yield as compared to pure substrates of either rice husk or cow dung and production of biogas depends to a large extent on the choice of feed stock.
Study concludes that biogas generation directly depends on the initial characteristics of the substrates (its digestibility) and type of bacterial present responsible for digestion processes. Among the substrates of the study, cow dung produced the highest biogas with better rate and contains more nutrients than rice husk; furthermore, the performance of biogas production from cow dung substrates was the best among the substrates in our study. The study also revealed that rice husk requires enrichment with inoculum and minimal pre-treatment of drying and grinding to enhance the biogas yields. The use of enriched and pretreated rice husk for biogas generation would provide a good energysource for those residing in the coastal areas, which face the menace of this waste in the environment. Blending of cow dung and rice husk produce more biogas than when digested individual substrates this way can lead to improved digestion and enhancement of biogas production through synergistic effects. The outcome of this research also suggests that rice husk does not produce gas as compared to cow dung; however, the residue obtained from the digestion process can be a source of good fertilizer for crop.