Date of Award
8-2026
Document Type
Thesis
Degree Name
Master of Science (MS)
Department
Environmental Engineering and Earth Science
Committee Chair/Advisor
Sudeep Popat
Committee Member
David Ladner
Committee Member
Kevin Finneran
Abstract
Medium Chain Carboxylates (MCCs), including caproate and caprylate, are valuable chemicals in various industries that can be produced biologically through an identified chain elongation pathway called reverse β-oxidation. During lipid degradation in anaerobic co-digesters at wastewater treatment plants, methane production is maximized to ensure the successful breakdown of the lipids. It remains unclear whether the anaerobic conversion of lipids possesses the potential to produce MCCs, and this study sought to evaluate the potential using anaerobic co-digester sludge from a full-scale wastewater treatment plant. Batch assays were conducted using the sludge from the plant as inoculum, as well as palmitic acid, glycerol, propionate, and ethanol/acetate, under varying methanogenic inhibition, pH, and buffering conditions. Production of hydrogen and methane, as well as measurements of pH and volatile fatty acid concentrations were monitored to study the relationship between methanogenesis, syntrophic β-oxidation, and reverse β-oxidation. The inoculum was found to have chain elongation potential because in non-inhibitory conditions, transient caproate formation was observed in multiple combinations of substrate, while methane was the ultimate favored electron sink. Methanogenic inhibition using 2-bromoethanesulfonate increased hydrogen partial pressure and suppressed methane production, but strong methane inhibition inhibited syntrophic β-oxidation, thus affecting the production of acetate and furthermore, the potential for chain elongation to occur. pH adjustment and increased buffer capacity promoted more favorable conditions for caproate production, allowing methanogens to scavenge hydrogen to continue β-oxidation. The results of this study suggest that chain elongation will occur from the anaerobic conversion of lipids only when acetate production, hydrogen partial pressure, methanogenesis, and pH are at favorable levels. Complete suppression of methanogenesis was not an effective strategy for promoting MCC production. Instead, these findings support that controlled methanogenetic activity and pH stabilization provide a more favorable environment for reverse β-oxidation to occur during anaerobic lipid conversion. Semi-continuous reactor operation should be investigated as a means of sustaining chain elongation and improving MCC recovery from anaerobic co-digester sludge and the conversion of lipids.
Recommended Citation
Boyer, Erin, "Evaluating the Potential for Chain Elongation to Produce Medium Chain Carboxylates From Anaerobic Conversion of Lipids" (2026). All Theses. 4848.
https://open.clemson.edu/all_theses/4848