Discharge of Fat, oil and grease (FOG) from the food processing industries and slaughterhouses into the waste streams creates hindrance in the sewer systems and the cross-section of pipes and interceptors of the wastewater treatment plants (WWTPs) due to its deposition. Approximately 98% of pipeline blockages and sewer overflow are occurred by FOG deposition each year in the United States. Despite of its negative effect, the lipidic nature of FOG can be convertible (95%) to biogas through anaerobic fermentation. In this study, the improvement of the hydrogen production was investigated after the supplementation of FOG (10% wt/wt TS) in the anaerobic fermentation of domestic wastewater sludge. Hydrogen yield was significantly improved to 31 mL g-1 VS during FOG fermentation, which was 34% higher than the control (23 mL g-1 VS). Relatively higher hydrogen productivity (Rmax) was also observed in FOG reactors (2 mL d-1) with increased cumulative hydrogen production by 67%. Increased hydrogen production was directly correlated with the degradation of long chain fatty acids (LCFAs) of FOG as FOG provides higher organic matter (97%) in the form of LCFAs (71%) than sludge alone (65%). Especially, carboxylic chain elongation was occurred with the production of medium-chain carboxylates (MCCs) such as Isocaproate, Isocaprylate and Caprylate during 22 days batch fermentation. Chain elongation to MCCs also contributed to the gaseous hydrogen production. The high-throughput sequencing analysis of 16S rRNA genes showed the abundance of the phylum Firmicutes and Bacteroidetes in the FOG reactors due to their predominant role in FOG degradation and utilization through hydrogenogenic acidogenesis. Thus, supplementation of FOG to wastewater sludge improved the hydrogen yield along with the production of value added MCCs.

Utilization of waste fat, oil and grease (FOG) for the improvement of fermentative hydrogen production

255th National Meeting (2018)

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