(00709)Anaerobic digestion of long-chain fatty acids (oleic, palmitic, stearic)with whey protein as the emulsifier

摘要

Long chain fatty acids are major lipid constituents. In this study, anaerobic digestion of oleic, palmitic or stearic acid (5 g/L each)emulsified with whey protein (20 g/L)was examined in continuous (batch-fed)stirred tank digesters with 2 L working volume. Anaerobic co-digestion of oleic acid displayed high biogas yield (0.47 L/gCOD), compared to palmitic (0.42 L/gCOD)and stearic acid (0.30 L/gCOD). Oleic acid, despite its high biodegradability resulted in major inhibition of the acetoclastic methanogens, as demonstrated by VFA accumulation and by the methanogenic activity assay. Biogas production from palmitic acid was stable, with a biogas yield close (90%)to the theoretically expected values. This was not the case however for stearic which displayed negligible biodegradability. Application of the ADM1 revealed the maximum degradation rate constant of each LCFA. Based on the results of this study it can be concluded that stearic acid degradation is the rate limiting step of the anaerobic digestion process, and this attributed to its low solubility and thus bioavailability.