Per- and polyfluoroalkyl substances (PFAS), often referred to as "forever chemicals," are a large and complex group of synthetic chemicals that have been in use since the 1950s. These substances are known for their strong carbon-fluorine bonds, which make them incredibly resistant to breakdown, allowing them to persist in the environment indefinitely.
Understanding PFAS is crucial because they can pose serious health risks and are widely present in our water and soil. This post will explore what PFAS are and how pyrolysis can destroy PFAS. Get ready to learn about these persistent pollutants and why they matter to you.
PFAS are found in a wide array of products, from non-stick cookware and waterproof clothing to lubricants and coatings on electronics. Alarmingly, forever chemicals have also been detected in food and beverages. For instance, in 2023, Prime Hydration, a popular sports drink brand, faced a class action lawsuit over the presence of PFAS in their grape-flavored drinks. The company was sued in the Southern District of New York for "misleading and deceptive practices" and is now facing a $5 million lawsuit. Read more: PFAS in Prime Hydration.
The persistence of PFAS extends beyond their initial and intended use. When PFAS-containing products are discarded, these compounds often end up in landfills, composting sites, and waste facilities. From there, they can leach into soils and groundwater, accumulating as non-biodegradable, toxic compounds. Extended exposure to such chemicals has been shown to cause various adverse health effects, including an increased risk of some cancers, impacts on the immune system, and altered metabolism.
This makes it critical to prevent the reintroduction of PFAS into the environment when managing waste materials like biosolids and sewage sludge. Destroying PFAS is essential to ensure safe disposal of these materials.
Pyrolysis Process: A Solution to PFAS Contamination
One promising method for destroying or removing PFAS from waste materials is pyrolysis. At elevated temperatures above 600°C, PFAS compounds become volatile, meaning they can vaporize out of solids. Instead of incinerating these substances, which can release harmful gases into the atmosphere, high-temperature pyrolysis (HTP) offers a more environmentally friendly solution.
The HTP process involves heating organic materials to over 800°C in an oxygen-free environment. This auto-thermal process effectively removes PFAS contaminants from dried biosolids, converting these now PFAS-free biosolids into a higher-value biochar output. Not only does this method eliminate PFAS from the solid fraction, but it also decarbonizes the entire biosolids management process by generating renewable gases that can fuel the process and provide excess energy for drying.
Our Success with PFAS Elimination
At CHAR Tech, we have been actively testing the impact of HTP on PFAS destruction , and the results are promising. Pilot-scale tests conducted with biosolids from three wastewater treatment facilities across the USA confirmed the elimination of 31 common types of PFAS compounds. The analysis demonstrated complete elimination of PFAS in the biocarbon after HTP at 700°C, with 99.7% elimination in the liquids and pyrolysis gas outputs. Higher temperatures proved to be even more effective in both volatilizing and destroying PFAS compounds.
After undergoing pyrolysis, the biosolids are transformed into biochar, which is classified as “Class A Exceptional Quality” under the U.S. Environmental Protection Agency (EPA) 40 Code of Federal Regulations (CFR) Part 503.32(a). This means the biochar meets stringent standards for pathogen reduction and metal limits, making it suitable for land applications, including soil amendment, agricultural nutrition, and carbon sequestration.
CHAR Tech is also collaborating with Synagro, a leader in biosolids management and recycling solutions, to integrate the HTP process for PFAS elimination. This collaboration marks a significant step forward in ensuring the safety and sustainability of biosolids recycling. Read more about this project: CHAR Tech Partners with Synagro to Eliminate PFAS in Biosolids.
As we continue to confront the challenges posed by PFAS, the importance of developing and implementing effective mitigation strategies cannot be overstated. By leveraging advanced methodologies like pyrolysis, we can take meaningful steps toward reducing the environmental impact of these persistent chemicals and ensuring a safer, more sustainable future.