Emission of PFOA of a Waste-to-Energy incinerator

October 2017

Nowadays thousands of synthetic organic fluorine substances are produced for a wide range of applications; one of the large groups are per- and polyfluoroalkyl substances (PFASs) with an estimate of 3000 compounds. Since the late 1990s, multiple long-chain PFASs, in particular perfluorooctanoic acid (PFOA) and perfluorooctanesulfonate (PFOS), have attracted worldwide attention in the scientific and regulatory community and among the public. PFOS and its precursors are now listed and PFOA and related precursors are being evaluated for listing, under the Stockholm Convention on Persistent Organic Pollutants (POP).

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Taylor et al (2014) [3,4] find incineration of fluorotelomer-based polymers does not result in the formation of detectable levels of PFOA under conditions representative of typical municipal waste combustor (MWC) and medical waste incinerator (MWI) operations in the U.S. Therefore, waste incineration of these polymers is not expected to be a source of PFOA in the environment.

 

In a study of ToxicoWatch 2015 - 2018, the flue stack was analyzed on fluorinated compound PFOS and PFOA in a long-term sampling program of AMESA. PFOS was only detectable (above LOQ) in one shutdown event with 8,23 pg/Nm3.

PFOA was detectable in all (n=6) long-term sampling periods (433 – 794 hours, total 3,929 hours). Minimum-maximum is 0,0134 – 0,004 ng/Nm3, average emissions are 0,002 ng/Nm3, which results in a yearly load estimate of 40,1 mg PFOA and 4,9 mg PFOS. No correlation could be found with transient conditions, like start-up of a shutdown, in all modes of operations PFOA was detectable. However, PFOA and PFOS should not be detectable at all in modern waste incineration processes [3]. Finding of PFOA in the stack can be an indicator of incomplete combustion, i.e. not complying with a minimum 2 seconds residence time at 850 °C, or they could be the result of bypassing during start-ups and shutdowns, observed during 20,748 hours of long-term sampling with AMESA.

 

Essentially, 'small' emissions of PFOA from a steady state operational incinerator are just the tip of the iceberg when all the potential 'upset' conditions are considered. It conveys the impression that modern incinerators cannot fully destroy UPOPs like PCDD/F, PBB, PCB or even PFOA - even under optimal operating conditions. Maybe temperatures in the post-combustion zone should be elevated anyhow to the level of 1100 degrees for a true complete destruction of all relevant UPOPs.

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PolyBrominated Biphenyl (PBB) decompose above 300 degrees C, however, two times PBB was detected during steady state conditions 0,038 – 0,133 ng/Nm3

Also this study of 20,139 hours sampling shows, the average contribution of dl-PCB is 8,5% of the total TEQ (n = 36). This is a factor 3 higher than Sakurai et al (2003) find of the contribution of coplanar PCBs from combustion sources, 3% in the total TEQ PCDD/F/dl-PCBs (see poster TW UPOPs). Together with the results of the heterogeneous temperatures in the after combustion zone, makes it reasonable the incinerator is not complying the two seconds residence above the 850  degrees. This is one of the pillars of the Stockholm Convention to eliminate or to reduce the emissions of persistent organic pollutants (see poster temperatures). 

In 2014 NGO ToxicoWatch was one of the signatories of the 'The Madrid Statement on Poly- and Perfluoroalkyl Substances (PFASs).