Decarbonizing Concrete: PHNX Materials Turns Coal Waste into Sustainable Solution

The Unexpected Climate Benefit of Coal Ash

For the past century, coal-fired power plants have demonstrably contributed to environmental issues. Impacts ranging from climate change and acid rain to health problems like black lung and heart disease have positioned these plants largely as detrimental forces.

However, a potential, albeit surprising, climate benefit resides within the byproducts of these plants – specifically, in the ash they produce.

Utilizing Fly Ash in Concrete Production

According to Krish Mehta, co-founder and CEO of PHNX Materials, “Ash can be used to replace up to 30% of cement.” Substituting cement with fly ash from coal plants offers a pathway to significantly reduce the carbon footprint associated with concrete production.

PHNX Materials has developed a process to remove sulfur and carbon, which are considered impurities by concrete manufacturers, from fly ash. This preparation renders the ash suitable for use in concrete while simultaneously creating valuable resources like sulfur and aluminum.

Recent Funding and Industry Context

The startup recently secured a $2.5 million seed funding round, as exclusively reported by TechCrunch. This investment was spearheaded by Divergent Capital, KdT Ventures, and Overture, with additional participation from Jane Woodward.

The use of ash in concrete isn’t a new practice. Historically, the Ancient Romans utilized volcanic ash, and for over a century, state transportation departments have incorporated fly ash into their projects. For instance, Caltrans mandates a minimum of 25% fly ash content in concrete used for its infrastructure.

The Role of Fly Ash in Concrete Stability

Jorge Osio-Norgaard, PHNX Materials co-founder and CTO, explains that fly ash plays a crucial role in stabilizing concrete mixtures. Without ash, a chemical reaction can occur, transforming the aggregate – the small rocks within concrete – into an expansive gel that can cause cracking.

“When you invest a billion dollars in a highway or bridge, longevity is paramount,” Osio-Norgaard stated. “Fly ash contributes significantly to achieving that long-term durability.”

Challenges Arising from Power Plant Closures

The decline in coal-fired power plants has led to a reduction in the availability of ash for concrete companies. Coal’s contribution to U.S. electricity generation has decreased from 51% to 15%.

This reduction has spurred a new industry focused on coal ash harvesting. Companies are now actively recovering fly ash from storage sites, processing it minimally, and selling it to concrete producers. However, the quality of recovered ash varies, leading to a fly ash shortage and subsequent price increases.

Impact on Concrete Composition and Carbon Emissions

Consequently, concrete companies have reduced the amount of fly ash in their mixes to approximately 8%, according to Mehta. While they could utilize up to 30%, they are compensating with increased cement usage, which is nearly twice as expensive per ton as fly ash.

This shift not only potentially compromises the durability of the concrete but also elevates its carbon footprint. Cement production releases CO₂ both from the chemical processes involved and from the fossil fuels used to generate the necessary heat. The EPA estimates that one ton of U.S.-produced cement releases around 0.8 tons of carbon dioxide.

PHNX Materials’ Approach to Decarbonization

“We believed that unlocking a new supply of ash represented the most scalable and rapid method for decarbonizing this sector,” Mehta explained.

PHNX Materials’ process directly extracts sulfur and aluminum from fly ash sourced from landfills. The company is also exploring methods to recover rare earth elements. The processed ash will be sold to concrete manufacturers, while the extracted sulfur, aluminum, and other compounds will be marketed to relevant industries. Sulfur, for example, can be utilized in fertilizer production.

By addressing the impurities present in the majority of the 843 fly ash landfills across the U.S., and potentially generating revenue from these byproducts, PHNX Materials aims to provide the concrete industry with a more sustainable alternative. “We felt that unlocking a new supply of ash was the most scalable and quickest way to decarbonize the sector,” Mehta reiterated.