At WEFTEC in Chicago this week, much of the conversation turned to the greenhouse gases too often overlooked in wastewater. Methane and nitrous oxide (N₂O) are not side issues — they are the forces that will define whether the sector delivers on its climate commitments or risks losing credibility. What struck me most was how quickly these hidden emissions are moving from research into practice, and how urgent it is for utilities to act.

Methane: A Test of Trust and Safety

The sector has built a compelling narrative around biogas: turning waste into renewable energy as a climate solution. However, that promise collapses if methane leaks. Once losses reach 7–9%, biogas can be more carbon-intensive than conventional energy.

The stakes go beyond carbon accounting. Methane is a combustible gas, and unchecked leaks pose serious health and safety risks for workers, surrounding communities, and plant infrastructure. A single high-profile incident — whether detected on a satellite map or triggered by an accident on-site — could undermine confidence in biogas projects and set the industry back years.

The tools to prevent this are well established. Utilities can pair top-down technologies such as satellites and drones with ground-based monitoring to pinpoint leaks. Routine leak detection and repair (LDAR), stronger digester operations, and targeted upgrades are all achievable today. These practices reduce emissions, strengthen safety, and build public trust.

Nitrous Oxide: The Overlooked Giant

N₂O is often the largest single source of emissions in wastewater treatment, especially where electricity supplies are already low-carbon. Yet it remains largely unmeasured and unmanaged.

The hierarchy of action is clear: reduce nitrogen loading upstream, optimize processes to prevent N₂O formation, recover nitrogen where possible, and reserve destruction technologies for high-concentration cases. Importantly, low N₂O emissions are not just a climate benefit — they signal more stable, resilient treatment processes.

International peers are already moving. Carbon markets, emissions pricing, and large-scale monitoring investments are advancing elsewhere, while the U.S. risks falling behind if these emissions remain unaddressed.

The Path Forward

The conversations at WEFTEC left me with several clear takeaways. Methane and N₂O must be treated as central to climate strategy, not as afterthoughts. Monitoring needs to be deliberate and sustained. Many solutions can come from operational improvements, not only capital projects. And none of this succeeds without engaging operators early, equipping them with training and tools, and aligning emissions reduction with utilities’ core priorities of safety, stability, efficiency, and compliance.

The leadership imperative is unmistakable. Both methane and N₂O are measurable and manageable. What’s needed now is to move beyond pilots and embed these practices into standard operations. The tools exist, the risks are clear, and the time to act is now. The sector’s climate credibility — and its safety record — depend on whether we can confront these hidden emissions and bring them under control.