title: Kinetics and methane gas yields of selected C1 to C5 organic acids in anaerobic digestion.
abstract: Volatile fatty acids (VFAs) and other short-chain organic acids such as lactic and pyruvic acids are intermediates in anaerobic organic degradation. In this study, anaerobic degradation of seven organic acids in salt form was investigated, including formate (C1), acetate (C2), propionate (C3), pyruvate (C3), lactate (C3), butyrate (C4), and valerate (C5). Microbial growth kinetics on these organic acids were determined individually at 37 °C through batch anaerobic digestion tests by varying substrate concentrations from 250 to 4000 mg COD/L. The cumulative methane generation volume was determined real-time by respirometry coupled with gas chromatographic analysis while methane yield and related kinetics were calculated. The methane gas yields (fe, mg CH4 COD/mg substrate COD) from anaerobic degradation of formate, acetate, propionate, pyruvate, lactate, butyrate, and valerate were 0.44 ± 0.27, 0.58 ± 0.05, 0.53 ± 0.18, 0.24 ± 0.05, 0.17 ± 0.05, 0.43 ± 0.15, 0.49 ± 0.11, respectively. Anaerobic degradation of formate showed self-substrate inhibition at the concentrations above 3250 mg COD/L. Acetate, propionate, pyruvate, butyrate, lactate, and valerate did not inhibit methane production at the highest concentrations tested (i.e., 4000 mg COD/L). Microbes growing on acetate had the highest overall specific growth rate (0.30 d(-1)) in methane production. For comparison, the specific microbial growth rates on formate, propionate, pyruvate, butyrate, lactate, and valerate for methane production were 0.10, 0.06, 0.08, 0.07, 0.05, 0.15 d(-1), respectively.
authors.affiliation: Department of Civil and Environmental Engineering, University of Missouri, E2509 Lafferre Hall, Columbia, MO 65211, USA.
authors.forename: Yu
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Department of Civil and Environmental Engineering, University of Missouri, E2509 Lafferre Hall, Columbia, MO 65211, USA.
authors.forename: Qian
authors.initials: Q
authors.lastname: Chen
authors.affiliation: Department of Civil and Environmental Engineering, University of Missouri, E2509 Lafferre Hall, Columbia, MO 65211, USA.
authors.forename: Jialiang
authors.initials: J
authors.lastname: Guo
authors.affiliation: Department of Civil and Environmental Engineering, University of Missouri, E2509 Lafferre Hall, Columbia, MO 65211, USA. Electronic address: huzh@missouri.edu.
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Hu
mesh_terms: D000144:Acids, Acyclic / Q000378:metabolism*; D000693:Anaerobiosis; D056804:Biofuels; D019149:Bioreactors; D005232:Fatty Acids, Volatile / Q000378:metabolism*; D007700:Kinetics; D008697:Methane / Q000032:analysis / Q000378:metabolism*; D064307:Microbiota / Q000502:physiology*
chemical_list: D000144:Acids, Acyclic; D056804:Biofuels; D005232:Fatty Acids, Volatile; D008697:Methane
keywords: Anaerobic digestion; Kinetics; Organic acid; Respirometry; Volatile fatty acids