“Forever chemicals”, officially known as PFAS, are a large group of manmade chemicals that have been used for decades due to their useful properties. However, many of these chemicals are remarkably resistant to remediation, and can take years or even decades to break down in the environment. This is what earned them the name “forever chemicals” in the popular press. Now, startups and scientists are developing new technologies to help us properly destroy these chemicals and reduce their impact on the environment and human health.
Why do we need to destroy PFAS?
PFAS, (per- and polyfluoroalkyl substances), have become a major health concern recently. They are also a major environmental pollutant.
PFAS are used in a wide range of applications including:
- Greaseproof coatings on food packaging (think of the shiny layer on the inside of a microwave popcorn bag).
- Water repellant coatings on clothing (the ones that make the water bead up instead of making the coat wet).
- Non-stick coatings on cookware (although some modern versions no longer contain PFAS).
- Firefighting foams (AFFF) used to fight fuel fires (however, there is now a moratorium on the use of PFAS for these foams).
Furthermore, PFAS are widely used in manufacturing including making other PFAS compounds, in electronics, and in industrial lubricants.
PFAS health concerns
PFAS have been linked with a wide array of serious health issues. These include cancers, cardiovascular disease, developmental issues, infertility, and inflammatory bowel disease. There seem to be a few mechanisms of action to be concerned about:
- Inflammation: PFAS are shown to cause inflammation in several systems in the body including the bowel, arteries, and major organs.
- Endocrine disruption. Some PFAS compounds are structurally very similar to vital hormones in the body. This means they interfere with the body’s endocrine system.
- Cholesterol uptake: PFAS seem to be linked with an increased risk of dyslipidemia (high cholesterol).
- Carcinogenicity. Some PFAS are proven to be carcinogenic, and many others may exhibit carcinogenic effects. They are linked with cancers of the thyroid, liver, and kidney. There may also be a link with bladder cancer.
Why are PFAS hard to destroy?
PFAS compounds are based on organic atoms with fluorine atoms replacing some or all the hydrogen atoms. The resulting chemicals are incredibly stable because the carbon-fluorine (C-F) bond is so hard to break down. Even when they do break down, this often results in another shorter chain PFAS compound. As a rule of thumb, the longer the atom, the harder it is to break down. However, there are notable exceptions to this rule. The upshot is that certain PFAS compounds have been steadily increasing in our environment for decades.
One of the biggest worries is that many PFAS compounds include hydrophilic chemical groups that make them extremely soluble in water. So much so that one study of PFAS in the Great Lakes basin found PFAS in almost all the precipitation samples they collected. PFAS have also been found on every continent on the planet.
Technologies being tested
Many startups have spotted a growing market in technologies that are able to destroy PFAS compounds. There are all sorts of technologies that have been proposed. Here, we look at three of the most promising.
Supercritical water oxidation (SCWO)
In supercritical water oxidation, water is heated in a high pressure container until it becomes a supercritical fluid. You then introduce the contaminated PFAS waste stream. The resulting reaction is strong enough to break the C-F bonds.
It relies on heating and pressurising water to such a high degree that it enters a new state of matter: a so-called supercritical state. When the PFAS waste stream is introduced, it breaks the carbon-fluorine bonds. This allows the fluorine to bond with the water instead and results in the destruction of the PFAS.
Electrochemical oxidation (EO) technology.
Electrochemical oxidation uses a traditional technique, electrolysis, to cause the PFAS-contaminated water to ionise and trigger oxidation. The water breaks down into hydrogen and oxygen, along with high energy hydroxyl radicals. The PFAS is then oxidized either at the anode or via the hydroxyl radicals.
Plasma technology
This approach uses a plasma (a high energy stream of ionized gas) to break down the PFAS molecules. The reaction occurs in a specially designed plasma reactor and works to progressively shorten the PFAS molecules. Eventually, they become short enough to be able to degrade naturally.
PFAS destruction vs reduction
Up to now, most commercial approaches to PFAS reduction have involved high performance active carbon filters. The problem here is that these filters eventually become saturated with the PFAS. The compounds are trapped, but you then have the problem of how to dispose of the resulting waste safely. All too often, the only solution is to bury it in sealed landfill sites. Other filtration methods, such as reverse osmosis, also suffer from the same drawback.
Issues with PFAS destruction
There are three significant issues we need to solve with the current approaches to PFAS destruction.
- Byproducts: Many approaches generate extremely hazardous byproducts, such as hydrogen fluoride vapor. This is extremely toxic, even in small doses.
- Low volumes: As things stand, none of these approaches can work at industrial scale. This may change over the coming years, but these technologies are still in their infancy.
- High energy. Often, these approaches require significant amounts of energy to break down the C-F bonds. This could make them uneconomic at large scales.
Reality not just research
PFAS-degradation is still a completely new field. However, some startups are already ahead of the curve.
Aquagga
Aquagga uses an approach called HALT (hydrothermal alkaline treatment). This uses an alkaline liquid heated under pressure to extremely high temperatures in order to degrade the PFAS. In June, they announced that they had successfully completed a proof-of-concept demonstration with the DOD for destroying old stocks of PFAS-based AFFF foam.
374Water
374water is based in North Carolina. They are developing SCO technology for use in waste water plants. The high levels of PFAS in drinking water mean that waste water plants act as concentrators of PFAS as they filter and separate out fluids and solids. 374Water is running a commercial trial with the City of Orlando, FL, to test their technology. Currently, they can only process a tiny fraction of the waste, but early results are promising.
Looking to the future
Manufacture of some more toxic forms of PFAS is illegal in both the US and EU. However, globally, PFAS continues to be manufactured and used at a huge scale. This, coupled with the incredible longevity of PFAS, means we are only on the cusp of the PFAS problem. As a result, techniques to reduce or eliminate PFAS are likely to become ever more common over the coming years.
One notable issue is the slow growth in approaches designed to eliminate PFAS from the human body. Cambiotics, a spinout from the University of Cambridge, has developed a nutraceutical treatment that uses natural gut bacteria to bind and eliminate PFAS from the body. NeutraOat is working on a specialized fiber supplement designed to prevent your body from absorbing plasticizer, BPA, and PFAS. The upside of this is a reduction in PFAS in people taking the treatments. But the unwanted side effect is to increase the amount of PFAS entering the waste water system. In turn, this drives an increase in the need for PFAS destruction in waste water treatment.
