Be Ambitious: Durham Region's Water and Wastewater Net-zero GHG Roadmap

Durham Region initiated a project to develop a long-term greenhouse gas (GHG) management strategy for its water and wastewater (W&WW) facilities over the next 20 years, in alignment with the Region's Corporate Climate Action Plan (CCAP) goals of 20% below 2019 levels by 2025, 40% below 2019 levels by 2030, and achieving net-zero emission for corporate operations by 2045. The Region's GHG inventory was expanded to include applicable Scope 1 and 2 emissions conform with the 2019 Intergovernmental Panel on Climate Change (IPCC) Refinement, and selected Scope 3 emissions related to chemicals, biosolids, and incineration ash management (Table 1). Development of the GHG inventory considered the industry best practice, applicable local and federal GHG reporting requirements, the availability and accuracy of quantification methodologies for each source, the level of complexity and difficulty in quantifying these emissions, and whether mitigation measures are available (such that the contribution to GHG reduction goals can be reasonably quantified). The updated 2019 base year emission for Region's W&WW sectors was 45,913 tonnes CO2e, including 85% Scope 1, 6% Scope 2, and 9% Scope 3 emissions. Wastewater contributed to approximately 92% of the total emissions, while water accounted for the remaining 8%. It is recognized that setting GHG reduction targets for all emission sources is currently not practical, given the difficulty and uncertainty associated with the quantification methods. Therefore, only Scope 1 and 2 emissions were included for GHG objective setting; Scope 3 emissions will continue to be tracked to assist decision-making, and target setting can be considered in the future as improved methodologies can data sources become available. Figure 1 shows the base year Scope 1 and 2 emissions by source. Wastewater process N2O emission represents the single largest GHG source. The very low Scope 2 emissions (electricity) are attributed to the low-intensity electricity grid in Ontario (largely consisting of nuclear, hydro, and renewables). An industry scan of current best practices was completed to identify net-zero solutions applicable to the Region. The long list was screened using a set of must-meet criteria that considered compatibility, technology readiness level, and GHG reduction potential based on the 80/20 rule (i.e., 80% of emissions likely resulted from 20% of the processes). Twelve (12) sites/systems were shortlisted for detailed evaluation, including 6 wastewater pollution control plants, 4 water supply plants, the wastewater collection system, and the drinking water distribution system. These sites/systems together accounted for more than 90 percent of the total Scope 1 and 2 emissions. Monitoring and mitigating process N2O emissions was identified as one of the most critical strategies. A two-year continuous N2O monitoring program was initiated, with two liquid-phase N2O sensors installed at the Duffin Creek Water Pollution Control Plant (co-owned by Durham and York Regions) in August 2023; initial results indicated variances over time and at different locations within the same treatment train. Examples of other shortlisted net-zero solutions include mitigating CH4 emissions through leak detection and repair, converting sludge storage lagoon to gravity thickener to reduce fugitive CH4 emission, biogas upgrade to renewable natural gas, thermal hydrolysis pre-treatment coupled with post-aerobic digestion to increase biogas generation while mitigating process emissions, sewer thermal recovery, and solar photovoltaic generation. Future GHG projections were developed for business-as-usual and based on implementing the recommended projects, as shown in Figure 2. Although it is possible to meet the 2025 and 2030 GHG reduction targets set out in the CCAP (if implementing all the identified projects), additional reductions will be required to meet the net-zero target by 2045, through further process optimization and/or adopting innovative net-zero solutions in the long term as they become more developed. A two-tiered approach was recommended, including the baseline objectives considering the current best practices available, and stretch goals aligned with the CCAP targets, as illustrated in Figure 2. The project is expected to be completed in early 2024. The presentation will include the final recommendations of major projects, the implementation plan by 2045, and the refined short-, medium-, and long-term GHG reduction targets for Durham Region's water and wastewater systems. Results from the first 14 months of the continuous N2O monitoring program will also be presented.