The effect of organic loading rates (OLRs) on the performances of food wastes and maize husks anaerobic co-digestion in continuous mode

Owamah, H.I and Izinyon, O.C. (2015) The effect of organic loading rates (OLRs) on the performances of food wastes and maize husks anaerobic co-digestion in continuous mode. Sustainable Energy Technologies and Assessments, 11. pp. 71-76. ISSN 2213-1388

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Abstract

A continuous anaerobic digestion experiment was carried out to investigate the co-digestion of 75% foodwaste and 25% maize husk at different organic loading rates (OLRs) of 1–4.5 gVS/L/d. Results obtainedshowed that pH fluctuated between 7.3 and 7.5 and total alkalinity (TA) between 0.4 and 6.7 gCaCO3/L, indicating that the system was not inhibited by acidification. The range of the ratio of volatilefatty acid (VFA) to TA of 0.06–0.25 was also well below 0.4 and showed that the anaerobic co-digestionwas stable and feasible. Though there was no significant difference (p< 0.05) between biogas yields atOLRs of 3.5 and 4.5 gVS/L/d, the methane content at OLR of 4.5 gVS/L/d was higher than that of3.5 gVS/L/d and suggests that carbon dioxide producing microorganisms were more active in OLR of3.5 gVS/L/d. The OLR of 4.5 gVS/L/d was therefore found to be the most satisfactory for large scale oper-ation of anaerobic digesters for co-digestion of food waste and maize husk. From a separate batch test, theaverage biogas yield of 0.50 ± 0.04, 0.24 ± 0.02 and 1.31 ± 0.07 L/gVS were obtained from digesters A, Band C, respectively, indicating that the addition of maize husk to digester C significantly improved theproduction of biogas from food waste when compared to the biogas yield of digester A that containedfood waste alone. Digester B with 100% maize husk was by far the least performed digester.

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