Coal-fired power plants have caused considerable damage over the past century. From climate change to acid rain, black lungs, and heart disease, they were generally on the debit side of the ledger.
But literally hiding in the ashes is like a climate savior.
“Ash can be used to replace up to 30% of the cement,” Krishmeth, co-founder and CEO of PHNX Materials, told TechCrunch. By replacing cement with concrete, fly ash from coal plants can eliminate a significant portion of the material’s carbon footprint.
PHNX material has devised a method to strip off sulfur and carbon fly ash. By drawing out these compounds, PHNX prepares fly ash and creates a new source of sulfur and aluminum, another compound found in fly ash, while still being ready for concrete companies.
The startup has recently raised a $2.5 million seed round. TechCrunch learned exclusively. The round was led by Divergent Capital, KDT Ventures and Overture, bringing participation from Jane Woodward.
Ash has been used in concrete for thousands of years. The ancient Romans used volcanic ash, and over the past century or so, the state’s transport sector has changed from coal mills to fly ash. For example, Caltrans requires a minimum of 25% fly ash for the concrete used in the project.
The secret behind Fly Ash is that it helps stabilize concrete mixes, said Jorge Osio Norgaard, co-founder and CTO of PHNX Materials. In the absence of ash, certain chemical reactions allow the aggregate (a small rock of concrete) to expand and turn the concrete into a gel that can crack.
“If we spend $1 billion on highways and bridges, we hope that it will last for the next 100 years,” says Osio-Norgaard. “Fly ash helps us achieve that goal.”
The closure of coal-fired power plants has significantly reduced the amount of ash available to specific companies. Coal was used to provide 51% of all electricity in the United States. Today, it produces 15%.
These closures created new industries for the harvest of coal ash. Companies scrutinize, dig, lightly process ash pits for high quality fly ash and sell to specific companies. But not all ashes fit the specifications, Mehta said, and it created a fly ash shortage that caused prices to skyrocket.
As a result, specific companies dial the amount of fly ash in the mix to about 8%, he said. They may be using up to 30%, but instead make up for the difference with additional cement.
That trade not only endangers the durability of concrete, but also increases carbon footprint. Cement releases CO2 from the chemical reactions that form it and the fossil fuels used to provide heat to promote the reaction. According to the EPA, one tonne of cement produced in the US releases around 0.8 tonne of carbon dioxide.
“We felt that unlocking the new supply of ashes was the most scalable and quickest way to decarbonise the sector,” Meta said.
The PHNX process takes fly ash directly from the landfill and extracts sulfur and aluminum. The company is also considering ways to extract rare earth elements. The ash will then be sold to concrete manufacturers and industries related to sulfur, aluminum and other compounds. For example, sulfur can be used in fertilizers.
By dealing with the impurities that race most of the US 843 fly ash landfills and potentially benefiting, PHNX believes it can offer low-carbon options to specific industries. “We felt that unlocking the new supply of ashes was the most scalable and quickest way to decarbonise the sector,” Meta said.