Quantifying Fugitive GHG Emissions At Metro Vancouver’s Lulu Island WWTP

[b]Introduction[/b] Metro Vancouver's Climate 2050 Strategic Framework established regional targets of achieving 45 percent reduction in greenhouse gas (GHG) emissions by 2030 and becoming carbon neutral by 2050. In 2025, a two-stage multi-method monitoring project was launched at Metro Vancouver's Lulu Island WWTP (LIWWTP) to identify and quantify fugitive methane (CH₄) and nitrous oxide (N₂O) emissions. Results will inform a Fugitive Emission Management Plan for the plant, develop tangible measures to reduce emissions, and guide strategies at Metro Vancouver's other WWTPs. Efforts to monitor and ultimately reduce fugitive CH4 emissions will lead to additional revenue and cost savings. LIWWTP is a secondary treatment plant with a design average dry weather flow capacity of 89 ML/d. Major treatment processes include primary and secondary treatment, disinfection, sludge thickening, anaerobic digestion and dewatering. Biogas is used in boilers to meet on-site heating demand. Excess biogas is upgraded to produce renewable natural gas for grid injection. Secondary treatment is designed for BOD removal only using trickling filters (TF) followed by solids contact tanks (SCT). N2O emissions are expected to be minimal, while multiple sources of fugitive CH4 emissions are likely. [b]Approach and Methodology[/b] Standard protocols for quantifying GHG emissions do not exist for wastewater facilities. Some measurement methods allow both CH4 and N2O, while others only measure one. Some technologies are great at spotting leaks but poor at quantifying emissions, while other technologies may be ideal for short-term campaigns but not financially or technically viable for year-round continuous monitoring. A multi-method approach is adopted, allowing for source-level and area/site-level quantification, as well as seasonal campaigns and long-term, continuous monitoring. The project uses commercially available technologies and innovative solutions (Figure 1) through academic partner University of Calgary (UoC). The project is being carried out in two stages: [b]Stage 1 (April - May 2025):[/b] This stage used initial monitoring to determine the most important locations and appropriate technologies for longer-term monitoring in Stage 2. Efforts included near-continuous site-level monitoring using a QLM light detection and ranging (LiDAR) camera, and a one-week campaign based on dispersion modelling by the UoC. [b]Stage 2 (August 2025 – March 2026):[/b] Multiple methods are being deployed, including the QLM LiDAR camera, seasonal site-level campaigns using tracer correction (Aerodyne) and dispersion modelling (UoC), process unit level CH4 leak detection and quantification by Montrose Environmental using optical gas imaging camera and Hi-Flow Sampler integrated with Tunable Diode Laser Absorption Spectroscopy, and process unit assessment from various odour control units (OCUs) using gas canister sampling and/or flux chamber on bark filers (Jacobs/UoC/ALS). Other innovative site-level methods to be tested include low-cost metal oxide sensors, Open-Path Tunable Diode Laser (TDL) camera and satellite imaging for CH4 quantification (UoC). [b]Stage 1 Results[/b] Estimated site emissions during the monitoring period based on QLM's system were 20,000 kg CH4. Most emissions were from three sources: 66% from the biogas upgrade system water scrubber pressure safety valve (Figure 2); 14% from a combination of near-range air vent (exhaust from biogas upgrade system water scrubber) and more distant emissions from TF3 (Figure 3); and 7% from ground-based biofilter 3 which receives air from TF4 and TF pump station 2 (Figure 4). UoC concentration mapping identified CH4 hotspots around ground-level biofilters and around the Biogas Upgrade System (Figure 5 example). N2O was not measured above ambient levels – this was expected as the plant is not operated for nitrification. CH4 losses based on biogas production was estimated to be between 4 and 7 percent. This is higher than the default value currently used by Metro Vancouver (which is based on the OWWA/WEAO GHG Inventory Tool), but within the typical range identified in the IPCC protocol (0-10%). QLM-based estimates from a 4-day sampling period in April 2025 are nearly twice those from UoC data. However, the two methods are not directly comparable; UoC measurement data are extrapolated from ground-level readings during site operating hours only, while QLM data are extrapolated from near-continuous monitoring. [b]Key Outcomes and Next Steps[/b] Both Stage 1 methods identify OCUs and the biogas upgrading system as key CH4 sources. The near-continuous monitoring and dispersion modelling approaches aligned fairly well, and Stage 2 work will be able to further develop these comparisons. The first and second phase of Stage 2 field campaign were completed in late August 2025 and early December 2025, respectively. One more seasonal campaign is scheduled for March 2026. In addition, two continuous methods (QLM LiDAR and low-csot sensors) will be deployed for site-wide CH4 measurements. Full results from Stages 1 and 2 will be presented at the conference. Results will be used to create a monitoring-based plant emissions inventory, provide a comparison to IPCC guideline-based calculations, develop recommendations on GHG emission reduction actions, and to inform process-based emission monitoring and reduction at other Metro Vancouver WWTPs.