Transforming Cement: A Sustainable Approach by Ryan Gilliam

Every year, cement ranks as the second most consumed material on Earth after water, yet its production drives massive carbon emissions. By harnessing existing technology and infrastructure, we can reshape this ubiquitous industry into a sustainable powerhouse.

The Cement Conundrum

Cement acts as the “glue” in concrete, binding aggregates into structures that last decades. Yet this indispensability comes with a steep climate cost: cement production is responsible for nearly eight percent of global CO2 emissions. If cement were a country, it would rank third in emissions—surpassing India and trailing only the United States and China. These staggering figures underscore the urgent need for breakthrough solutions. To deliver real impact, any sustainable cement technology must leverage the raw materials, capital assets, and distribution channels already in place, meet existing regulatory standards, and remain price-competitive with traditional cement. Only by addressing these four pillars—materials, infrastructure, compliance, and economics—can we avoid green-technology premiums and drive widespread adoption in an industry that prizes reliability as much as performance.

Understanding Cement's Carbon Footprint

At the heart of cement’s carbon intensity lies limestone, which naturally contains 44 percent solid CO2 by weight. Producing clinker, the key intermediate, requires heating limestone to around 1,450 degrees Celsius in kilns fueled by coal or natural gas. This process liberates CO2 twice over: first when the fossil fuel burns, and again when the limestone is decarbonated. In fact, the calcination reaction alone accounts for roughly half of the emissions embedded in conventional cement. Beyond the chemistry, life-cycle assessments reveal additional emissions from quarrying, grinding, and transport—reminding us that any credible sustainable cement solution must tackle emissions holistically, from rock face to ready-mix truck.

Biomimicry and Calera's Innovation

Nature has long solved the puzzle of carbon uptake and mineral formation. Coral reefs and mollusk shells extract dissolved CO2 from seawater to build calcium-carbonate structures with remarkable strength. Seventeen years ago, a company called Calera pioneered a carbon-capture-and-utilization technology inspired by these processes. By reacting captured CO2 with calcium-rich feedstocks, Calera produced a white powder containing 44 percent CO2 by weight—similar to limestone, but in a reactive, spherical form known as vaterite. When mixed with water, vaterite transforms into stable aragonite or calcite, mirroring cement hydration.

“Instead of treating CO2 as waste, we treat it as a resource—unlocking new pathways for sustainable building materials.”

Although Calera’s pilot successfully demonstrated the chemistry, it initially struggled to compete on cost and scale against legacy cement. The key lesson: innovation must align seamlessly with industry economics and operations.

Integrating Innovation with Existing Practices

Our approach reimagines Calera’s process not as a standalone plant, but as an integrated module within existing cement facilities. By retrofitting carbon-capture reactors to the exhaust streams of traditional kilns, we can intercept CO2 emissions at the source and convert them back into a cementitious product. This hybrid material can either supplement Portland cement in standard concrete formulations or, in optimized mixes, replace it entirely. Crucially, this integration leverages the same quarries, grinding mills, and distribution networks that cement companies already operate, thereby minimizing capital overhead and regulatory hurdles. The result is a drop-in solution that can reduce per-ton CO2 emissions by up to 70 percent when firing with fossil fuels—and achieve fully carbon-neutral cement if combined with renewable energy or green hydrogen in the kiln.

Scaling Sustainable Cement Production

Commercial-scale deployment hinges on collaboration with established cement producers. In early 2024, Forterra—a four-year-old startup spun out from our pilot work—commenced operations at its first commercial plant in Northern California. Partnering with a major cement manufacturer, Forterra demonstrated that the carbon-capture reactors could be installed on an existing line without disrupting production schedules. Within months, the plant processed over 100,000 tons of cementitious material, validating the technology’s scalability and cost competitiveness. Looking ahead, Forterra plans additional facilities in Europe and Asia, tapping into dense infrastructure corridors where sustainable construction demand is rising. Concurrently, a growing cohort of startups and research consortia is advancing complementary carbon-capture technologies, digital twins for kiln optimization, and novel low-clinker cement chemistries. Together, these efforts form a rapidly maturing ecosystem poised to decarbonize one of the hardest-to-abate sectors.

Conclusion: A Roadmap to Massive Carbon Reductions

Our roadmap is straightforward: collaborate with existing manufacturers, retrofit proven technology, and deploy at scale to curb the projected four billion tons of cement-related CO2 emissions over the next few decades. By anchoring sustainable innovation in established practices, we can accelerate market adoption and avoid costly infrastructure duplication.

Actionable Takeaway: Adopt carbon-capture retrofits in existing cement plants to achieve up to 70 percent emission reductions per ton—paving the way to carbon-neutral cement without sacrificing performance or economic viability.

As the cement industry evolves, what incentives, policies, and partnerships will move us closer to a truly sustainable built environment?