Advancements in PFAS-Free AFFF formulations
Firefighting formulations used for military operations on Department of Defense (DoD) installations historically contain per- and polyfluoroalkyl substances (PFAS) in order to meet the performance requirements of MIL-F-24385F. However, the PFAS in aqueous film forming foam (AFFF) formulations are difficult to degrade and can migrate to groundwater, potentially posing risks to human health and the environment. To manage these risks, the DoD is working to develop alternative PFAS-free fire-suppression methods.
SERDP and ESTCP have launched a number of projects over the years to research and demonstrate viable replacements for AFFF. Our Principal Investigators are considering many different approaches to new formulations. A snapshot of some of these efforts is captured below.
Nine proof-of-concept efforts were funded by SERDP in 2017 and 2018. These projects broke ground on testing possible PFAS-free replacements for AFFF. Dr. Joseph Tsang with the Naval Warfare Center Weapons Division tested polysaccharide copolymers and nanoparticles as potential foam components that were expected to be sustainable, non-toxic and water-dispersible ( Project Webpage). In order to determine ideal components for alternative formulations, Dr. John Payne is broadening our understandings of firefighting foam chemical processes by analyzing the relationships that determine effective surfactant formulation, surface chemistry, foam physical properties, and fire performance ( Project Webpage).
At the U.S. Naval Research Laboratory, Dr. Ramagopal Ananth is leading an effort focused on the use of siloxane surfactants from commercial sources to develop a fire-suppression solution with low environmental impact ( Project Webpage). Under their first SERDP project, Ananth and his team discovered that siloxane surfactants failed to rapidly and completely cover burning and non-burning fuel pools. They are now pivoting to synthesize siloxane surfactants with a systematic structural variation of the head and tail groups to ensure the foam fully expands across the fuel pool surface.
In his recently completed project focused on identifying surfactants that spread over the hydrocarbon surface and include metal carbonate particles, Jaspreet Dhau with Molekule, Inc. ( Project Webpage) found that aqueous solutions of alkyl imidazolium or alkyl pyridinium ionic liquids as well as alkyl sulfates formed stable foams capable of extinguishing small hydrocarbon fires. These solutions demonstrated spreading coefficients close to or higher than the DoD minimum, drainage time falling within the target range, and enhanced foam stability when combined with the metal carbonate particles.
Investigators are also looking into other surfactants, including polymer-based surfactants at Virginia Tech ( Project Webpage) and surfactants with organosilicate nanostructures at the Naval Air Warfare Center, China Lake ( Project Web Page). Aromatic polymers have been found to inhibit flames through the formation of a char, while polyhedral oligosilsesquioxanes, thermally stable silicate materials, could be transformed into surfactants to increase water solubility.
As the knowledge-base increased, so did DoD’s investment in PFAS-free AFFF alternatives. In 2019, an additional 6 projects were initiated to investigate PFAS-free fire suppression agents. Building on previous projects, researchers have had more opportunities to test and compare commercially available PFAS-free formulations.
Jerry Back at Jensen Hughes, Inc. is working to compare and quantify the capabilities of AFFFs and commercially available PFAS-free alternatives, which will coincide with the development of a database to increase access to this information ( Project Webpage). Dr. Satya Chauhan with Battelle Memorial Institute is not only testing multiple commercial off the shelf PFAS-free formulations against MIL-PRF24385F specifications, but also alternative firefighting technologies (such as compressed air form and ultra-high pressure) to determine if these technologies will be compatible with new alternative foams ( Project Webpage). In order to assess how PFAS-free forms might perform against large-scale fires, Brian Lattimer with Jensen Hughes is conducting a series of bench-scale tests to predict whether these commercial or developmental formulations have the potential to meet MIL-F24385F fire suppression and burnback performance requirements ( Project Webpage).
To learn more about DoD-funded research on PFAS-free fire suppression agents, check out this developing list of SERDP projects and ESTCP demonstrations addressing PFAS-free solutions. Research, development and demonstrations will continue over the next several years in order to meet performance requirements and keep our warfighters safe.