Coal-fired power plants have long been implicated in numerous environmental crises, contributing to climate change, acid rain, and health issues such as black lung disease and heart problems. However, hidden within the waste produced by these facilities lies a potential ally in the battle against climate change: fly ash.
Krish Mehta, co-founder and CEO of PHNX Materials, has highlighted that fly ash can replace up to 30% of cement in concrete mixtures. This substitution significantly reduces the carbon footprint associated with concrete production. PHNX Materials has developed innovative methods to purify fly ash, removing undesirable impurities such as sulfur and carbon, thus preparing it for use in concrete manufacturing. By refining fly ash, the company simultaneously generates new sources of sulfur and aluminium, both valuable in various industries.
Recently, PHNX Materials secured a $2.5 million seed funding round led by Divergent Capital, KdT Ventures, and Overture, with additional investment from Jane Woodward. The utilisation of ash in construction has historical precedence; ancient Romans incorporated volcanic ash, while modern transportation departments increasingly adopt fly ash from coal plants. California’s transportation agency, for instance, mandates at least 25% fly ash in the concrete used for state projects.
The efficacy of fly ash lies in its ability to stabilise concrete mixtures. Jorge Osio-Norgaard, co-founder and CTO of PHNX, noted that without the stabilising properties of fly ash, concrete can degrade due to chemical reactions that lead to expansion and cracking. As such, fly ash is integral to the longevity of infrastructure projects expected to last a century or more.
The closure of many coal-fired power plants has significantly decreased the availability of fly ash for the concrete industry, reducing its share of electricity generation in the U.S. from 51% to just 15%. This decline has birthed a new industry focused on harvesting coal ash, where companies sift through ash pits to gather quality fly ash. However, due to high demand and variable purity levels, this has also led to a shortage, resulting in concrete companies scaling back the fly ash content in their mixtures, which now averages around 8%. This reduction necessitates increased use of cement—almost double the cost of fly ash—which not only jeopardises the quality and durability of concrete but also escalates its carbon emissions.
Mehta emphasised that addressing the fly ash supply issue is a key strategy for decarbonising the construction sector. PHNX’s innovative process extracts valuable sulfur and aluminium while also exploring options to recover rare earth elements from fly ash. The company plans to sell the refined ash to concrete manufacturers, along with the extracted compounds to other industries, such as fertiliser production. Through this approach, PHNX aims to transform an environmental liability into a sustainable resource, potentially creating a lower-carbon solution for the concrete industry and contributing to broader climate change mitigation efforts.
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