Analysis shows no significant PFAS emissions under approved waste incineration conditions

Fluoropolymers have become an integral part of modern society, both in industrial and consumer applications. At the end of their useful life, these high-performance materials can become both industrial and domestic waste.

Researchers at Karlsruhe Institute of Technology (KIT), in collaboration with international partners, analyzed the contribution of fluoropolymer waste incineration to the release of small-molecule, non-polymeric fluorinated compounds.

Experiments using KIT’s BRENDA incinerator show that fluoropolymers are almost completely destroyed during combustion at temperatures and residence times typical of European incinerators. The study was published in the journal Chemosphere.

In contrast to fluoropolymers, also known as “polymer PFAS” and considered non-mobile and non-bioaccumulative, used in medical products, semiconductors, aerospace, automotive, chemical processing, etc. “Molecular PFAS” are being integrated into a wide range of decentralized consumer applications.

They are used, for example, as water-repellent impregnations in textiles, clothing, and paper (pizza boxes, hamburger boxes, baking liners). The PFAS substance group includes approximately 10,000 substances, but fluoropolymers are only a small subgroup of 38 substances.

Some low-molecular-weight PFAS are hazardous to health and have been linked to organ damage and cancer. Low molecular weight PFAS can accumulate in groundwater and soil, causing environmental problems in many places and impacting human health, whereas fluoropolymers have much larger molecular weights, making them less harmful to health and the environment. It is considered safe.

Researchers study the efficiency of the combustion process

A research team led by Dr. Hans-Joachim Gehrmann from the KIT Institute for Technical Chemistry (ITC) analyzed whether and how much low-molecular-weight PFAS are released into the environment by incineration of fluoropolymers. .

In collaboration with Gujarat Fluorochemicals, India’s leading manufacturer of fluoropolymers, the scientists conducted the test using the BRENDA pilot-scale incineration facility at KIT. The researchers burned fluoropolymers in tests and measured PFAS concentrations in scrubber water, ash, and exhaust gas.

The purpose of the experiment was to determine whether standard combustion conditions in municipal and industrial waste incinerators are sufficient for complete mineralization of fluoropolymers.

Typical fluoropolymer mixtures

The researchers conducted experiments at two different temperatures. One is 860 degrees Celsius, which corresponds to the European household waste incineration standard, and the other is 1,095 degrees Celsius, which is the typical temperature for hazardous waste incineration. In both cases, the minimum residence time of the flue gases in the combustion chamber was 2 seconds.

“We have demonstrated that a fluoropolymer reduction rate of over 99.99% can be reached at a combustion temperature of 860 degrees Celsius and a residence time of 2 seconds. “This means we have achieved almost complete mineralization of the polymer,” Gehrman said.

“Combustion at 1,095 degrees Celsius did not result in significantly higher reduction rates, suggesting that high temperatures do not have a significant effect on the petrification of fluoropolymers.”

For the combustion chamber experiments, the team used materials commercially available around the world, including polytetrafluoroethylene (PTFE, also known as Teflon), polyvinylidene fluoride (PVDF), perfluoroalkoxy alkanes (PFA), and fluoroelastomers (FKM). We selected a representative sample covering 80% of the fluoropolymers used in .

Samples were taken from the flue gas at several stages of the combustion process: at the exit of the combustion chamber, downstream of the boiler, and in the chimney. The team also analyzed samples from wastewater and solid residues. Analytical methods such as gas chromatography and mass spectrometry were used to identify and accurately quantify PFAS.

“This result is good news that fluoropolymers can be completely removed in municipal waste incineration according to European standards,” Gehrmann said. However, he said, “There are other ways in which PFAS can enter the environment, and these need to be analyzed and evaluated.”