Associate Professor Magnus Gålfalk and Professor David Bastviken at Linköping University are behind the study, which examined twelve Swedish wastewater treatment plants that use sludge digestion to produce biogas. The survey was conducted using drones equipped with specially manufactured sensors that measure emissions of methane and nitrous oxide.
The researchers have concluded that emissions were approximately 2.5 times higher than the UN body IPCC's calculation model shows.
"This is a completely new way of measuring greenhouse gas emissions. We have been able to measure with high precision over large areas," says Bastviken.
Bastviken wants to be clear that the treatment plants should not be portrayed as environmental criminals - he believes that they are doing what they can to reduce emissions but that they have lacked the right tools and data.
"They're doing a great job. This new technology is not really about detecting emissions, but about the ability to fix emissions. It's a technology to help the sector," he says.
Methane and nitrous oxide emissions occur primarily when the digestion process is complete and the remaining sludge is piled up. Sludge storage is done to reduce the amount of harmful microorganisms before the sludge is used as fertilizer, for example.
Water treatment plants that receive wastewater from households and industries account for approximately 5 percent of human-caused methane and nitrous oxide emissions, according to the IPCC.
