Anaerobic Digestion of Cassava (Manihot Esculenta) Waste: Effects of Inoculum on Biogas Production Rate

ABSTRACT

In this paper, cow manure fluid was used as inoculums to investigate biogas production rate from anaerobic digestion of cassava peel at mesophilic temperature (280C). The anaerobic experiment was conducted using six batch digesters (D1, D2, D3, D4, D5 and D6) each of 20L capacity for 40-day hydraulic retention. Each digester, was loaded with 5kg of cassava peel (CP) and 0%, 10%, 20%, 30%, 40% and 50% of inoculum to CP. Hashimoto model was used to obtain the digestion kinetic parameters. The results of the study showed that inoculums influenced the rate of biogas production, showing variations in biogas production, correlation coefficient (R2) and in first-order decay constant (k). The average cumulative biogas production was in the range of ~2358 to 4010ml/kgVS for 10% to 50% inoculum. The R2 and k for D1 was 0.959 and 0.359 D1 (without inoculum), 0.990 and 0.371 for D2 (10% inoculum) and 0.991 and 0.371 for D3 (20% inoculum), 0.951 and 0.356 for D4 (30% inoculum), 0.992 and 0.372 for D5 (40% inoculum), and 0.990 and 0.371 was obtained for D6 loaded with 50% inoculum. Despite variation in biogas yields from different inoculums, biogas production obtained from anaerobic digesters loaded with inoculums were still lower compared with that without inoculum.

Keywords: Biogas, Cassava waste, Inoculum, Bioenergy, Kinetics

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