Technical BRIEF

INNOVATIVE RESEARCH FOR A SUSTAINABLE FUTURE

Per- and Polyfluoroalkyl Substances (PFAS):
Incineration to Manage PFAS Waste Streams

Background

Per- and polyfluoroalkyl substances (PFAS) are a very large
class of man-made chemicals that include PFOA, PFOS and
GenX chemicals. Since the 1940s, PFAS have been
manufactured and used in a variety of industries in the
United States and around the globe. PFAS are found in
everyday items such as food packaging, non-stick stain
repellent, and waterproof products, including clothes and
other products used by outdoor enthusiasts. PFAS are also
widely used in industrial applications and for firefighting.
PFAS can enter the environment through production or
waste streams and can be very persistent in the
environment and the human body. PFAS have many and
varied pathways into waste streams, presenting challenges
for ultimate disposal. Determining the appropriate method
for ultimate disposal of PFAS wastes is a complex issue due
to their volatility, solubility, and environmental mobility
and persistence. EPA is currently considering multiple
disposal techniques, including incineration, to effectively
treat and dispose of PFAS waste.

Options and Considerations for the
Disposal of PFAS Waste via Incineration

One potential disposal method for PFAS waste is through
high temperature chemical breakdown, or incineration.
Incineration has been used as a method of destroying
related halogenated organic chemicals such as
polychlorinated biphenyls (PCBs) and ozone-depleting
substances (ODSs), where sufficiently high temperatures
and long residence times break the carbon-halogen bond,
after which the halogen can be scrubbed from the flue gas,
typically as an alkali-halogen. PFAS compounds are difficult
to break down due to fluorine's electronegativity and the
chemical stability of fluorinated compounds. Incomplete
destruction of PFAS compounds can result in the formation
of smaller PFAS products, or products of incomplete
combustion (PICs), which may not have been researched
and thus could be a potential chemical of concern.

Incineration of halogenated organic compounds occurs
via unimolecular decomposition and radical reaction. For
unimolecular decomposition, fluorinated organic
compounds require temperatures above 1,000°C to
achieve 99.99% destruction in 1 second residence time.
Unimolecular decomposition of highly fluorinated
organics most likely occurs through breakage of C-C or C-
F bonds (Tsang et al., 1998). The most difficult
fluorinated organic compound to decompose is CF4,
requiring temperatures over 1,400°C, but is easily
monitored, making it a potential candidate for
destructibility trials.

Fluorinated organic compounds can also be degraded via
incineration by free radical initiation, propagation, and
branching mechanisms. Although hydroxyl radical
reaction with hydrocarbons is a common combustion
flame-propagating mechanism, the strength of the C-F
bond makes this pathway unlikely and would instead
leave atomic hydrogen, formed at high temperatures, as
the likely radical reacting with the carbon-bonded
fluorine.

U.S. Environmental Protection

August 2019

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Radical reactions are more likely for chloroalkanes than
fluoroalkanes, due to the lower bond energy of C-CI (Tsang
et al., 1998). If formed, the extremely high
electronegativity of fluorine radicals results in their quick
combination with other radical species, preventing flame-
sustaining free radical propagation and branching
processes. This propensity to terminate free radical
chemistry make PFAS effective fire suppressants.

The stability of perfluorinated radicals leads to higher
concentrations and correspondingly increased propensity
to recombine, creating larger molecules that are products
of incomplete combustion (PIC) and distinctive from the
original fluorinated organics. These reactions are promoted
by partial organic combustion resulting from insufficient
temperatures, time, and mixing. In addition, the presence
of catalytic surfaces, often metals, promotes further
reaction and PIC formation in post-combustion regions.

This scenario has been most studied related to the
formation of polychlorinated dibenzo-p-dioxins and
dibenzofurans (PCDDs/PCDFs) in the cool-down regions of
waste incinerators.

The effectiveness of incineration to destroy PFAS
compounds and the tendency for formation of fluorinated
or mixed halogenated organic byproducts is not well
understood. Few experiments have been conducted under
oxidative and temperature conditions representative of
field-scale incineration. Limited studies on the thermal
destructibility of fluorotelomer-based polymers found no
detectable levels of perfluorooctanoic acid after 2 second
residence time and 1,000°C (Yamada et al., 2005; Taylor et
al., 2014). Emission studies, particularly for PICs, have been
incomplete due to lack of necessary measurement
methods suitable for the comprehensive characterization
of fluorinated and mixed halogenated organic compounds.

capture and identify PFAS compounds and their thermal
decomposition byproducts, and the efficacy of emission
control technologies are areas of targeted research.
These efforts, in cooperation with states and industries,
is aimed at proper disposal of PFAS-laden wastes without
media-to-media transfer or environmental release.

References

Tsang, W.; Burgess, D.R., Jr.; Babushok, V. (1998) On the
Incinerability of Highly Fluorinated Organic Compounds,
Combust. Sci and Technol. 139:1, 385-402, DOI:
10.1080/00102209808952095

Yamada, T.; Taylor, P.; Buck R.; Kaiser, M.; Giraud, R.
(2005) Thermal Degradation of Fluorotelomer Treated
Articles and Related Materials, Chemos. 61, 974-984.

Taylor, P.; Yamada, T.; Striebich, R.; Graham, J.; Giraud, R.
(2014) Investigation of Waste Incineration of
fluorotelomer-based Polymers as a Potential Source of
PFOA in the Environment, Chemos. 110,17-22.

Contacts

•	Brian Gullett, PhD Gullett.brian(a)epa.Eov

•	Andy Gillespie. PhD Gillespie.andrew@epa.gov

Addressing Gaps in Research for PFAS
Waste

The extent to which PFAS-containing waste material in the
United States is incinerated is not fully documented or
understood. PFAS compounds are not listed as hazardous
wastes under the Resource Conservation and Recovery Act
(RCRA) nor as hazardous air pollutants under Clean Air Act
regulations, so they are not subject to the tracking systems
associated with these regulations.

EPA is currently considering multiple disposal techniques,
including incineration, to effectively treat and dispose of
PFAS wastes. EPA researchers are currently studying PFAS
incineration, sampling and analytical methods
development, and industrial field sampling. Research on
thermal stability of PFAS compounds, the ability to fully

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U.S. Environmental Protection Agency

August 2019

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