Generating biogas through the co-digestion of municipal organic waste and sewage biosolids at the Township of Georgian Bluffs Wastewater Treatment Works

The Township of Georgian Bluffs will partner with the Ontario Clean Water Agency (OCWA) to assess opportunities to retrofit and upgrade an anaerobic digester at the Derby (WWTW). The project aims to increase onsite renewable energy generation, divert waste from landfill and produce a valuable agricultural soil amendment (fertilizer). It also aims to improve the overall performance of the Derby WWTW while decreasing its operating costs. The Derby WWTW’s anaerobic digester facility was designed to accept and process both dewatered septage and solid feedstock. However, to date the facility has not operated at full capacity, due in part to limited feedstock. The township will assess options for introducing additional organic waste (e.g., source-separated organics from local communities) to increase the volume of biogas that can be produced. It will also evaluate new technologies and select the optimum technology for the planned upgrade. The study will also explore economically feasible options for using the increased biogas. The digester currently produces methane, which is used to generate electricity that is fed into the distribution grid for general use. The study will assess continuing to use the biogas for electricity production versus upgrading the biogas to renewable natural gas (RNG). This RNG would be comparable to fossil fuel natural gas, with equal or more methane content and energy value, and could be used onsite or injected into a natural gas pipeline. The increase in biogas production combined with the diversion of organic waste from landfill is expected to reduce the WWTW’s annual greenhouse gas emissions by approximately 11,568 tonnes of CO2e. Improved processes are also expected to reduce its energy consumption. Finally, using the digestate as a commercial fertilizer would mean not having to import mineral fertilizer, eliminating indirect greenhouse gas emissions related to production and transportation of that fertilizer. This feasibility study aligns with provincial policies focused on keeping food and organic waste out of landfills. It also supports the township’s Conservation and Demand Management Plan and its Energy Management Plan. Innovative aspects • The study aims to demonstrate the technical and financial feasibility of producing energy and a high-quality biosolid product from waste • The project will demonstrate the feasibility of this approach for small communities, and potentially be the first regional facility that produces both energy and a high quality digestate from waste materials • potentially be the first regional facility that produces both energy and a high quality digestate from waste materials Replicability • The findings of the feasibility study could be useful to other municipalities considering anaerobic digesters as part of their organics management systems • OCWA, the project consultant, will capitalize on its broad network in the Ontario wastewater sector to communicate lessons learned to municipalities across the province (Project description from original funding application)