Date

2021-2-12

Author

Çelik Çağlar, Tuğba

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In recent years, the renewable energy requirement is increased with the population increase and reduction of fossil fuel resources. In terms of biomass energy, corn waste constitutes the highest portion (33%) among crop wastes in the world. Thus, corncob, which is a corn waste and also non-food waste, has a great potential as a renewable energy source in the country. In this thesis study, the biochemical methane potential (BMP) of corncob (raw CC) was investigated initially and assessed by adopting co-digestion with feed (chicken manure (83%) and poppy (17%)), digestate or post-digestate and a pretreatment method, alkaline hydrothermal pretreatment at 240℃ (AHP_240). BMP of corncob was 103 mL CH4/g VSadded, and the highest synergistic effect was observed in Raw CC+Digestate reactors with 172 mL CH4/g VSadded. After AHP_240 method was applied, although sCOD of AHP_240 CC increased 17 times compared to Raw CC, methane yield of both AHP_240 CC and its co-digestion reactors did not significantly improve. After that, hydrothermal, alkaline and alkaline hydrothermal pretreatment methods were applied on Raw CC by using various temperatures, namely 150℃, 180℃ and 210℃ for their optimization. The hydrothermal pretreated corncob (HP CC) had 55-61% higher vi methane yield than Raw CC and there was no statistically significant difference among methane yields obtained for different temperatures studied. Thus, HP_150 method was selected as the optimum pretreatment method. Lastly, raw CC or hydrothermal pretreated corncob at 150 ℃ (HP_150 CC) were used as substrates with digestate in semi-continuous co-digestion reactors to investigate the optimum operational conditions, i.e., hydraulic retention time (HRT) and organic loading rate (OLR), leading to the maximum methane production. The highest methane yield of HP_150 CC and Digestate reactor was 392 mL CH4/g VSadded at an HRT of 10 days and OLR of 4.5 g VS/L.d. Raw CC apparently requires more than 15 days of HRT for higher solubilization. But, when HP_150 method is applied, HRT of 10 days seems to be profitable. This means smaller volume and lower capital cost for biogas plant. The use of HP_150 CC with Digestate in semi continuous reactors seems to be promising and feasible for methane production in large-scale biogas plant.

Subject Keywords

Corncob, Anaerobic co-digestion, Alkaline Hydrothermal Pretreatment, Biochemical methane potential (BMP), Semi-continuous reactor

URI

https://hdl.handle.net/11511/89580

Collections

Graduate School of Natural and Applied Sciences, Thesis