- Drones expose underestimated methane and nitrous oxide emissions in wastewater facilities.
- Researchers call for real-time measurement systems to guide global emission reduction efforts.
A new study from Linköping University has revealed that greenhouse gas emissions from wastewater treatment plants may be more than double previous estimates. Researchers used drones equipped with specialised sensors to detect high levels of methane and nitrous oxide, two potent greenhouse gases.
The study, led by Dr Magnus Gålfalk, found that many emissions from wastewater plants had gone unnoticed for years. With this discovery, scientists can now recommend more effective strategies to reduce emissions.
According to the UN Intergovernmental Panel on Climate Change (IPCC), wastewater facilities handling household and industrial sewage produce around five per cent of human-made methane and nitrous oxide.
The IPCC typically estimates these figures using models that are linked to population size and plant connections, rather than relying on direct measurements. As a result, the reported numbers often fail to reflect actual emission reductions accurately. Researchers argue that these models make it difficult for local authorities to show progress or justify investments in cleaner systems.
To address this, the team measured methane (CH₄) and nitrous oxide (N₂O) directly at twelve Swedish wastewater plants. The results were striking. Actual emissions were about 2.5 times higher than IPCC calculations suggested. Most gases were released after sludge digestion, particularly during storage. At this stage, methane leaks increased sharply, and nitrous oxide emissions rose unexpectedly.
Nitrous oxide proved to be a significant but underestimated threat. It has nearly 300 times the warming potential of carbon dioxide. The study also revealed that the climate impact of sludge storage matched methane.
These findings suggest that greenhouse gas emissions from wastewater treatment plants may have a significantly greater impact on global warming than previously thought. Therefore, adopting drone-based monitoring could ensure more accurate reporting, better policymaking, and more decisive climate action in the future.