Long chain fatty acids degradation in anaerobic digester: thermodynamic equilibrium consideration

Sungtaek Oh, Alastair D. Martin

Research output: Contribution to journalArticle

35 Citations (Scopus)

Abstract

The biological oxidations and reductions occurring in batch anaerobic digesters may approach equilibrium. The approach depends strongly on the activities of the micro-organisms present. The thermodynamics of linear long chain fatty acid degradation in a batch reactor was modeled. The substrates considered are the saturated fatty acids from acetic acid to stearic acid. From the thermodynamic perspective, the fermentation (acidogenesis and acetogenesis), decomposing the long chain saturated fatty acids to acetic acid though shorter chain acids, could not proceed spontaneously (ΔH ≫ 0 and ΔG ≫ 0). However the model suggests that the major driving force for the fermentation may be found in the methanogenesis. The model results show two distinct cases: (ΔS > 0 and ΔH > 0) and (ΔS < 0 and ΔH < 0), relating to spontaneous but endothermic and non-spontaneous but exothermic processes respectively. Where, spontaneous digestion is associated with high initial concentrations of LCFA and endotherm. This implies that the digestion of this type of substrate might be better facilitated by the supply of supplemental heat. The digestion of very low concentrations of LCFA is found to be non-spontaneous due in large part to the solubility of carbon dioxide. This implies that the digestion of this type of substrate might be enabled by selectively removing carbon dioxide.
Original languageEnglish
Pages (from-to)335-345
Number of pages11
JournalProcess Biochemistry
Volume45
Issue number3
DOIs
Publication statusPublished - Mar 2010
Externally publishedYes

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Thermodynamics
Fatty acids
Saturated fatty acids
Digestion
Fatty Acids
Acetic acid
Carbon Dioxide
Degradation
Acetic Acid
Fermentation
Carbon dioxide
Substrates
Stearic acid
Batch reactors
Solubility
Oxidation-Reduction
Oxidation
Acids
Hot Temperature

Cite this

Oh, Sungtaek ; Martin, Alastair D. / Long chain fatty acids degradation in anaerobic digester : thermodynamic equilibrium consideration. In: Process Biochemistry. 2010 ; Vol. 45, No. 3. pp. 335-345.
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Long chain fatty acids degradation in anaerobic digester : thermodynamic equilibrium consideration. / Oh, Sungtaek; Martin, Alastair D.

In: Process Biochemistry, Vol. 45, No. 3, 03.2010, p. 335-345.

Research output: Contribution to journalArticle

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