Drohnen zeigen, dass die Emissionen von Kläranlagen höher sind als erwartet. Wissenschaftler fanden heraus, dass die Emissionen von Methan (CH₄) und Lachgas (N₂O) aus diesen Anlagen – insbesondere aus der Schlammlagerung – etwa 2,5-mal höher sind, als internationale Klimamodelle vermuten lassen.

The study, published in Environmental Science & Technology, challenges long-standing assumptions used by the UN Intergovernmental Panel on Climate Change (IPCC). The IPCC currently estimates that WWTPs contribute roughly 5% of human-caused methane and nitrous oxide emissions, but their estimates rely on generalised emission factors rather than direct measurements.

The team used custom-built drones to measure emissions at 12 Swedish treatment plants that use anaerobic digestion – a common process for breaking down sludge and producing biogas. Their results revealed that large amounts of methane and nitrous oxide escape not during treatment itself, but later, when the sludge is stored to kill pathogens before being used as fertiliser.

The findings also highlight a previously overlooked source of climate pollution. Nitrous oxide, a greenhouse gas with nearly 300 times the warming potential of carbon dioxide, was found to be a major contributor – its climate impact was roughly equivalent to that of methane from the same sludge. These emissions had previously been assumed negligible in IPCC calculations.

Researchers say that using actual measurements rather than estimates would help local governments better track progress and justify investments in emission-reduction technologies

https://pubs.acs.org/doi/10.1021/acs.est.5c04780