The Danish EPA has funded several projects related to N2O emissions, providing a good starting point for reporting direct emissions in Scope 1. This is one of the reasons why Denmark has come far in gathering knowledge on N2O emissions, and several control strategies are now being tested and used at full-scale at Danish utilities.
The VARGA project is an example of one of these projects. It showcases the transformation of a traditional WWTP to a Water Resource Recovery Facility (WRRF) and can be visited as part of the World Water Congress & Exhibition technical tours programme: Tour 2, Avedøre WWTP.
More than three years of online data on N2O emissions have been collected, and a range of control strategies have been tested on-site. The results showed reductions of 30-80 percent (depending on the strategy) without compromising the nitrogen removal.
These experiences, together with the ambitious upcoming implementation of a limit on N2O in Denmark, are key tools for effective emissions reductions that can serve as inspiration for other countries on the road to Net Zero.
Don’t get lost in operation
As mentioned earlier, Scope 3 is now starting to gain traction in the wastewater sector. Here in particular we can find CO2 emissions from construction. We know from other sectors that this has a huge impact, especially when building completely new WWTPs. So far, Danish utilities have focused mostly on CO2 from operations as part of their reporting activities. But now is the time to start expanding our gaze to include wider climate goals and also consider indirect emissions.