A US-based cleantech startup, PHNX Materials, has devised an innovative method to transform toxic coal ash into a high-performance cement replacement. This process not only offers a new lease on life for the hazardous byproduct of coal combustion but also promises to drastically reduce the carbon footprint of concrete, one of the world's most polluting materials.

Headquartered in California, PHNX Materials has developed a proprietary technology to extract valuable compounds from fly ash, the fine, contaminated residue left after burning pulverized coal. Traditionally considered a hazardous waste, fly ash poses environmental risks and disposal challenges. However, PHNX's process purifies this ash, making it suitable for use as a supplementary cementitious material (SCM) in concrete production.

The environmental impact of this innovation is substantial. Cement production is a major contributor to global greenhouse gas emissions, accounting for approximately 8% of the total CO2 released worldwide. Notably, the production of one kilogram of conventional cement releases roughly one kilogram of CO2. Krish Mehta, co-founder and CEO of PHNX Materials, emphasizes the potential of their technology, stating, "Ash can be used to replace up to 30% of cement," thereby offering a direct pathway to significantly lower the carbon intensity of concrete.

The use of ash in concrete is not a novel concept. Ancient Romans utilized volcanic ash, known as pozzolana, to create remarkably durable concrete structures. More recently, transportation departments in the US, including California's Caltrans, have mandated the inclusion of fly ash (at least 25%) in concrete mixes for infrastructure projects to enhance durability and prevent destructive chemical reactions that can lead to cracking.

Jorge Osio-Norgaard, co-founder and CTO of PHNX Materials, underscores this benefit, explaining, "When you spend a billion dollars on a highway or on a bridge, you want it to last the next 100 years. Fly ash helps achieve that goal."

However, the increasing closure of coal-fired power plants across the US, with 21 shutting down in the last two decades, has led to a scarcity of readily available, high-quality fly ash. This shortage has compelled concrete manufacturers to reduce fly ash content, often substituting it with more cement. This shift not only increases costs but also compromises the strength and longevity of concrete while simultaneously raising its carbon emissions.

PHNX Materials' solution addresses this challenge by not only purifying the fly ash but also extracting valuable byproducts during the process. Their system targets common contaminants like sulfur and carbon, which are typically rejected by concrete producers. The removal of these impurities yields marketable materials such as sulfur and aluminium. Furthermore, the startup is exploring the potential extraction of rare earth elements, critical components for various clean energy technologies.

The promising nature of PHNX Materials' technology has attracted significant investment. The company recently secured USD 2.5 million in a seed funding round led by prominent early-stage investment firms Divergent Capital, KdT Ventures, and Overture, with participation from veteran cleantech investor Jane Woodward.