Date of Award

1-11-2022

Publication Type

Thesis

Degree Name

M.A.Sc.

Department

Civil and Environmental Engineering

Keywords

Anaerobic digestion, Biomethane recovery, Co-digestion, Distillery stillage, Pre-treatment, Source separated organics

Supervisor

N.Biswas

Supervisor

R.Seth

Rights

info:eu-repo/semantics/openAccess

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

Abstract

In Ontario, Canada, landfill capacity is rapidly decreasing, and inadequate waste management has resulted in increased greenhouse gas emissions and leachate volumes. Municipalities are left to design and implement their own organics waste management solution. Energy recovery through anaerobic digestion (AD) is attractive. However, AD can be costly for small and medium-sized communities. Two methods of improving economics of AD are studied in this thesis: co-digestion and pre-treatment of wastes.

Making use of industrial wastes can be an excellent method of supplementing AD of municipal wastes. The effect of mixing ratios on methane yield, substrate compatibility, and kinetics were studied for AD of distillery wet cake, source-separated organics (SSOs), and wastewater sludges. Mesophilic AD (37 °C) at an F/M ratio of 0.5 in a batch setup was performed using the AMPTS II unit. The addition of SSOs at higher ratios (50% and 75% VS) in the substrate mix resulted in a 14–15% higher yield per gram COD added, as compared to mono-digestion of wet cake. Mesophilic AD of the stillage and SSO mixtures resulted in a considerable lag phase, implying that degradation kinetics could be improved by acclimation of inoculum. This could help reduce operational costs and overall digestion time. Co-digestion studies revealed compatibility between the substrates, thus making AD a feasible alternative.

Microwave (MW) pre-treatment on distillery wet cake was investigated at temperatures of 50 °C, 70 °C, and 90 °C at 480 W and 1080 W, respectively. MW pre-treatment of distillery wet cake did not have a significant effect on the solubilization of COD and biomethane yield. At 480 W, 20–35% decreases in methane production rate were observed. At 1080 W, 22–30% decreases were observed. This suggests the production of phenolic compounds that slowed the degradation of stillage.

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