Research on PFAS in flue gases leads to
new discoveries

In a recent research project, IVL Swedish Environmental Research Institute tested new methods for measuring the hazardous substance PFAS in flue gases from Swedish waste-to-energy plants. The measurements show low levels of PFAS – instead, it was CFCs that accounted for the majority of the emissions. The discovery raises questions about how long these persistent fluorinated compounds, which were banned in the 1980s, will continue to circulate within society’s material flows.

CFCs were previously used, among other things, in insulation materials when this was still permitted. They remain present in older buildings and can be released when these are demolished, with the resulting demolition waste sent for energy recovery. At the same time, we cannot completely rule out the possibility that some formation may occur during incineration, or that background levels in the surrounding air may influence the results – for example, we detect CFCs in some background measurements, such as indoor air in laboratory environments. Overall, demolition waste nevertheless appears to be a likely explanation for why we are detecting CFCs in the flue gases says Johan Strandberg, project manager at IVL.

The Swedish project, which is supported by the U.S. EPA and the Swedish Environmental Protection Agency, is the first to measure PFAS in flue gases from waste-to-energy plants. In the study, three different measurement methods were tested under real-world operating conditions.

The measurements show that the concentrations of many individual substances vary significantly over time and between different sampling points in the stack. For the most volatile substances, the results are more consistent, but for other substances a single spot sample would often be misleading if the aim is to describe, for example, annual emissions.

When levels fluctuate this much, it becomes difficult to use single spot measurements as a basis for permit conditions or follow-up. It is likely and reasonable to expect that emissions of PFAS into the air will be regulated. But then we need monitoring that is designed to capture variations over time as well. Johan Strandberg.

Since PFAS are already present in society’s material flows, they will continue to appear in waste streams for many years to come – in the same way that CFCs are now detected as a result of past use. Therefore, it is important to develop methods that enable facilities to monitor and track their emissions reliably, even when concentrations are at low levels.

Our study shows that it is already possible today to measure these substances in flue gases, but also the limitations for how the results can be used. It provides guidance for how future monitoring programmes can be designed so that emissions of persistent fluorinated compounds can be tracked more systematically says Johan Strandberg.