Date

2022-11

Author

Odabaş, Yasin

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In this study we investigated the impact of granular activated carbon (GAC) application on anaerobic digestion (AD) process of cattle manure. Firstly, the effect of the presence of basal medium on cattle manure digestion was evaluated. It was observed that basal medium addition decreased methane yield and increased lag time. Then, for the enhanced cattle manure digestion, a metal-based conductive material, hematite (Fe2O3), and carbon-based material, GAC, were amended into the reactors. From the comparison of these two conductive materials, GAC was selected to be used in this study because of the higher performance in methane production. To study, amendment of GAC the optimum dosage was determined as 40 g/L experimentally. Further, the impact of GAC application on mesophilic (T = 35 oC) cattle manure digestion was investigated under both mixing and no mixing conditions and at two different food-to-microorganism (F/M) ratios of 1 and 3 in batch reactors. In the experimental tests, sand particle of similar size as in GAC were also added into the control reactors to assess the impact of supplying extra surface area for biomass attachment. The application of GAC increased the methane yield (139.0 ml CH4/g VSadded) by 28% at F/M ratio of 1 under mixing condition. While the enhancement in methane yield by sand amendment (115.6 ml CH4/g VSadded) was limited to 6% as compared to the Control1-mix (109.3 ml CH4/g VSadded). A higher increase was attained at F/M ratio of 3 under mixing conditions. In GAC amended reactor methane yield was 71% higher than the control, yet in sand amended reactor methane yield was only 15% higher than control. This implies that the performance enhancement in methane production and lag time is not merely due to surface area and can be attributed to the presence of conductive material. Further, we investigated the impact of GAC at psychrophilic temperature (~18 oC) conditions. GAC amendment increased methane yield by 12% and 26% in comparison to conventional anaerobic digestion reactor at F/M ratios of 1 and 3, respectively. Additionally, we have also investigated the impacts of biomass attached GAC, named as BioGAC, on the performance of psychrophilic manure digestion. BioGAC amendment enhanced methane yield by 21% and 33% compared to the control reactor at F/M ratio of 1 and 3, respectively. When GAC and sand applications were compared, higher increase in methane production was observed in GAC added reactors owing to its contribution to direct interspecies electron transfer (DIET) mechanism in the reactors. These results were also supported by cyclic voltammetry (CV) analysis. Finally, 16S ribosomal RNA based methods were used to identify the key microorganisms present in the psychrophilic reactors.

Subject Keywords

Cattle Manure, Anaerobic Digestion, Granular Activated Carbon, Methane, Direct Interspecies Electron Transfer

URI

https://hdl.handle.net/11511/101892

Collections

Graduate School of Natural and Applied Sciences, Thesis