Another highly relevant session was Decarbonizing Wastewater and Sanitation: Emissions, Resilience, and Climate Action, which closely aligned with EMISI’s work on methane emissions and greenhouse gas inventories.

Linda Strande presented research on determining population equivalents for non-sewered sanitation systems, challenging long-standing assumptions used in the Intergovernmental Panel on Climate Change methodology. Current IPCC calculations rely heavily on generalized assumptions such as person equivalent (PE), biochemical oxygen demand (BOD), and methane correction factors (MCFs). These assumptions may significantly overestimate greenhouse gas emissions from sanitation systems and consequently lead to oversized wastewater treatment infrastructure. Linda proposed shifting from PE-based calculations toward actual user numbers and localized field measurements. Her findings echoed discussions from participants studying pit latrine compositions in Japan, where waste characteristics were found to vary daily and seasonally, making steady-state assumptions increasingly unreliable.

Kelsey Shaw presented a study on measuring, scaling, and reporting methane emissions from low-cost non-sewered sanitation systems. Her work strongly resonated with what we are doing in EMISI. Methane (CH₄), a potent greenhouse gas contributing significantly to global warming, remains poorly quantified in non-sewered sanitation systems despite these systems serving nearly 58% of the global population. Current IPCC guidelines depend on generalized methane correction factors and per-capita assumptions that may not reflect real conditions. Through field measurements conducted in Canada and Uganda, the study found that conventional indicators such as BOD and COD showed little correlation with methane emissions. Instead, practical onsite indicators, such as scum depth, proved to be stronger predictors. These findings support the need for evidence-based climate policies and more accurate national greenhouse gas inventories for the sanitation sector. An interesting technical takeaway was that gas samples remain stable for up to a year when properly stored with standard gases.

Similarly, Aasim Mansuri shared findings on evaluating methane emissions across the sanitation service chain in India. Like EMISI, his team developed custom-built flux chambers to measure emissions from onsite sanitation systems, sewer networks, pumping stations, and drainage channels. Their results demonstrated that methane emissions in India are also underestimated by existing IPCC default values. By conducting localized field measurements in cities across Maharashtra, including Vita, Ichalkaranji, and PCMC, the study developed city-level emission factors and a standardized methodology for greenhouse gas accounting. The research contributes to climate mitigation strategies, resource recovery opportunities, and the development of more accurate urban emissions inventories.

Another plenary session that left a lasting impression on me was The Momentum Moment: Safely Managed Sanitation at Scale by Roshan Shrestha. Representing the Bill & Melinda Gates Foundation, he discussed how sanitation investments can drive climate resilience, public health, and sustainable urban development. Dr. Shrestha has spent more than 35 years advancing non-sewered sanitation, fecal sludge management, and citywide inclusive sanitation across the Global South, particularly in India, Bangladesh, and Nepal. His presentation emphasized the importance of strengthening systems, scaling climate-resilient sanitation infrastructure, and building cross-sector partnerships to accelerate progress toward sustainable development goals.