Researchers have created a volcanic rock–based formula that reduces carbon emissions by 67%, potentially providing a low-cost alternative to increasingly scarce cement additives.
Cement—a manufactured powder that binds concrete—is the most widely used construction material in the world, but also one of the most polluting, responsible for nearly 8% of global greenhouse gas emissions.
About a decade ago, Stanford geophysicist Tiziana Vanorio began investigating this issue after identifying unusual rocks beneath her childhood home in Pozzuoli. Located in a volcanic region, the area is shaped by intense underground chemical reactions driven by heat, pressure, and water. The rocks formed from volcanic ash—known as “pozzolan”—which has natural cement-like properties that allow it to bind materials under reactive conditions.
Inspired by Volcanic rock and Roman Concrete, Vanorio Develops New Cement Approach
The formations fascinated Tiziana Vanorio because they could endure significant deformation before breaking and shared a composition similar to Roman concrete, which supports long-lasting structures like the Pantheon.
An associate professor of Earth and planetary sciences at the Stanford Doerr School of Sustainability, Vanorio set out to replicate these properties in a newly engineered formula for modern cement.
To produce modern cement, industrial facilities heat crushed limestone—mainly composed of calcium carbonate—in large kilns. This process decomposes the limestone into lime and carbon dioxide. At higher temperatures, the lime then reacts with other oxides to create clinker, the primary active component of cement.
Limestone Alternative Identified to Cut Major Cement Emissions
The chemical transformation of limestone into clinker is responsible for nearly two-thirds of cement’s total carbon dioxide emissions, while fossil fuel–powered kilns produce the rest. The process is also inefficient: heating limestone turns roughly half of its mass into lime and releases the other half as carbon dioxide, meaning a large portion of the quarried material never ends up in the final product.
In 2021, Tiziana Vanorio identified a promising substitute for limestone that could significantly cut emissions during kiln heating.
She selected a type of igneous rock that is both abundant and nearly carbon-free, as volcanic processes had already removed its carbon during formation. When heated, these rocks release little to no carbon dioxide, instead producing an engineered pozzolan rich in chemical activators that collectively serve the role of lime—the essential ingredient in clinker.
Tiziana Vanorio named her low-carbon cement formula Phlego.
In collaboration with postdoctoral researcher Chengyao Liang, she designed it to meet industry standards while replicating the fibrous microstructures found in naturally cemented rocks, such as those beneath Pozzuoli. She is now working to commercialize this scientific breakthrough.
From Laboratory Discovery to Commercial Application
In 2025, Tiziana Vanorio received funding from the Stanford Sustainability Accelerator at the Stanford Doerr School of Sustainability, helping her and her team move Phlego closer to market. Through Accelerator programs and events, she connected with representatives from major global cement companies.
Vanorio noted that these interactions gave her valuable insight into the business side of cement. She realized that decarbonizing the industry is not only about developing low-carbon materials but also about managing risk—an understanding she described as a turning point.
Cement manufacturers typically operate on very tight profit margins, with kilns running continuously to meet demand for clinker. As a result, there is little flexibility to adopt new, more sustainable production methods if they introduce additional costs.
A shortage of Additives Alongside Rising Demand
Some cement producers have already modified their manufacturing processes by replacing part of the clinker with byproducts from industrial activities—such as coal combustion or metal refining—or with natural materials like volcanic ash. The industry uses these partial replacements, known as supplementary cementitious materials (SCMs), to lower clinker content.
This substitution reduces carbon dioxide emissions, supporting efforts to decarbonize cement production while preserving its strength and, in some cases, improving long-term performance.
However, SCMs are becoming harder to obtain. Fly ash supplies are declining as coal-fired power plants are phased out, while volcanic ash is available only in specific regions. In addition, the material’s composition can vary significantly, making quality control more challenging.
According to Tiziana Vanorio, ensuring both the availability and consistency of SCMs will be essential to reducing supply chain risks in low-carbon cement production.
Demand for SCMs is expected to grow at about 8% annually over the next decade, while supply continues to tighten. Engineered pozzolans such as Phlego could provide a dependable alternative, supporting the scaling and validation of low-carbon cement formulations.
The Future Role of Phlego in the Cement Industry
With support from the Accelerator, Tiziana Vanorio has acquired a kiln, expanded her team, and is collaborating with research engineer Rotana Hay to refine Phlego’s composition and performance as a supplementary cementitious material (SCM). She is also looking to bring in an entrepreneur with expertise in the cement industry.
Initially, Vanorio designed Phlego as a limestone substitute to cut clinker-related emissions and improve raw material efficiency. Now, she and Hay are also investigating its use as a low-cost, widely available alternative to the increasingly limited supply of SCMs. Engineers are designing the material to work reliably in both roles without requiring changes to existing cement plant infrastructure.
Vanorio explains that in difficult-to-decarbonize industries like cement, the quickest route to major impact is compatibility rather than disruptive change, noting that a drop-in solution significantly lowers deployment risk.
Read the original article: Tech Xplore
Read more: A new kitchen stove cooks food using water rather than natural gas