How the Sublime Process is Decarbonizing Cement Production

Revolutionizing cement: Electrified processes and zero-carbon promise for a low-emission future in construction.

By Medha deb

Created on Sep 26, 2025

Revolutionizing cement: Electrified processes and zero-carbon promise for a low-emission future in construction.

Cement is the backbone of global construction, but its production has long stood as one of the most carbon-intensive of all industries. With mounting pressure to reduce emissions and achieve net zero targets, a new technology from Sublime Systems is capturing attention. Using electricity and innovative electrochemistry at room temperature, Sublime’s process promises to remake cement as a fundamentally low-carbon material—without sacrificing performance or durability.

The Carbon Challenge in Cement Production

Cement, particularly ordinary portland cement (OPC), is a major contributor to global carbon emissions, responsible for approximately 8% of worldwide CO₂ emissions. This is mainly due to:

Use of limestone, which releases carbon dioxide when heated
High-temperature kilns that require vast amounts of fossil fuel energy

The traditional process involves heating a mixture of limestone, silica, alumina, and iron to temperatures exceeding 2,500°F (1,400°C) to form the chemical phases that give cement its strength. This results in substantial direct and indirect CO₂ emissions. As global construction booms, so does the pressure to decarbonize this essential material.

Introducing Sublime Systems and Its Revolutionary Approach

Sublime Systems, spun out of MIT, has introduced a new technique that fundamentally avoids the need for extremely high temperatures and carbon-releasing raw materials. Their vision is to enable construction to continue evolving, while drastically reducing its environmental footprint.

Key Innovations:

Electrochemical cement manufacturing at room temperature
Replacement of limestone with calcium silicate rocks or industrial byproducts, eliminating direct CO₂ emissions from decomposition
Process powered by renewable electricity, removing reliance on fossil fuel combustion

How Sublime’s Process Works

The process developed by Sublime Systems is a significant departure from the status quo. Instead of burning limestone in a kiln, Sublime uses low-value calcium silicate rocks (or industrial waste materials) and applies electricity to break them down into their base minerals. Here’s how the process unfolds:

Feedstock Selection: Uses minerals such as calcium silicate and industrial byproducts rather than limestone, removing the main source of carbon emissions.
Electrochemical Refining: An electrochemical cell, operating at room temperature and powered by clean electricity, separates the mineral components.
Elemental Extraction: The process yields purified mineral components—primarily calcium and silicates—as dry powders (Sublime Lime® and silicates).
Recombination: These mineral ingredients are blended to create a high-performance, durable cement powder, functionally equivalent to OPC.
Byproducts: Non-cementitious elements (magnesium, aluminum, iron) are recovered as pure co-products for other industries, reducing waste and supporting a circular economy.

Main Steps in the Sublime Process

Low-carbon materials are acquired (calcium silicate rocks or recycled industrial waste).
Feedstock enters an electrochemical cell.
Electricity is used to initiate chemical reactions, breaking down minerals at ambient temperature.
Purer cementitious constituents and valuable co-products are separated and collected.
Final cement is blended and shipped, ready to be mixed as concrete using sand, aggregate, and water onsite.

Comparison: Traditional vs. Sublime Cement Production

Aspect	Traditional OPC Production	Sublime Electrochemical Process
Temperature Required	~1450°C (2650°F)	Room Temperature
Feedstock	Limestone (CaCO₃)	Calcium silicate rocks, industrial byproducts
CO₂ Emissions	High, from both fossil fuel and raw material	Ultra-low to zero (when powered by renewables)
Energy Source	Coal/natural gas	Electricity (renewable-capable)
Co-products and Waste	50% of limestone lost as CO₂	Critical minerals recovered, nearly zero waste
Durability	Industry standard	Potentially higher durability (Roman cement inspiration)

The Environmental and Economic Benefits

Carbon Elimination: Sublime’s process avoids over 90% of the process emissions by eliminating both limestone decomposition and fossil fuel combustion. The process can be net-zero when powered by renewable electricity.
Energy Efficiency: Electrochemical cement production at ambient temperature is 30-40% less energy-intensive compared to traditional methods.
Low Waste: Instead of losing half the feedstock as pollution, almost all of it is transformed into valuable materials.
Product Versatility: The resulting cement is whiter, offering aesthetic and heat reflectivity advantages, and is more durable due to closely controlled composition.
Circularity: The process enables upcycling of industrial waste into high-value construction and manufacturing products.
Co-production of Critical Minerals: Valuable byproducts (magnesium, aluminum, and iron) can be sold for use in manufacturing and steel production.

Performance: Can Sublime Cement Really Replace OPC?

One critical requirement for any new cement is compatibility with existing concrete infrastructure. Sublime Cement is:

ASTM-compliant: Tested to meet standard specifications for performance and durability.
‘Drop-in’ Ready: Can fully replace OPC in any mix, enabling use in existing construction methods and codes without adjustment.
Long-Term Durability: Inspired by ancient Roman cement, it is potentially more resilient in diverse environments.

This ensures no compromise for builders or engineers when selecting a lower-emission material.

Scale and Potential Impact

Scale is a defining factor in the cement industry. Even the most eco-friendly process is only impactful if it can supply the billions of tons of cement required every year. Sublime Systems is actively working to:

Partner with established global cement companies to accelerate deployment
Build demonstration plants and pilot production facilities
Ensure cost-competitiveness at scale through energy and material savings

The technology directly aligns with international targets such as the International Energy Agency’s goal for net-zero emissions by 2050.

The Broader Vision: Beyond Low-Carbon Cement

Beyond providing a ‘green’ alternative to traditional cement, Sublime’s approach helps enable:

Domestic supply of critical minerals, reducing reliance on imports and supporting national manufacturing
Waste valorization: Upcycles industrial waste and low-value rocks, addressing both cement-related and broader waste challenges
Cleaner communities: Avoids airborne pollutants such as mercury, nitrogen oxides, and particulates traditionally emitted from kilns
Materials innovation: Refines the recipe of cement for greater performance, consistency, and aesthetic options

Voices from Industry Leaders

Nollaig Forrest, Chief Sustainability Officer at Holcim:

“The Sublime Systems team has developed a unique technology to decarbonize cement, cutting across the entire production process from the use of clean electricity to carbon-free raw materials. We are excited about this technology’s potential…this investment advances our strategy to decarbonize construction by scaling up the most innovative technologies across our operations.”

Dr. Leah Ellis, CEO and Co-Founder of Sublime Systems:

“In the cement industry, scale is everything. We are proud to collaborate with Holcim who supports our mission of swift and massive impact. By pairing Sublime’s technology with Holcim’s advanced global operations…we can scale up our impact together.”

Frequently Asked Questions (FAQs)

Q: Why is traditional cement so carbon-intensive?

A: Emissions come from both heating limestone to high temperatures—using fossil fuels—and from limestone itself, which releases CO₂ when decomposed.

Q: How does Sublime’s cement differ chemically from traditional OPC?

A: Sublime’s process yields cementitious minerals similar to those in OPC but avoids CO₂ release by using calcium silicate rocks instead of limestone and by electrochemical rather than thermal decomposition.

Q: Can Sublime Cement be used in conventional concrete mixes?

A: Yes. It is a drop-in replacement, meaning it can be used in any recipe or application substituting OPC one-for-one, while meeting or exceeding standard performance criteria.

Q: What is the main source of electricity for Sublime’s process?

A: While the process can use grid electricity, its emissions profile is lowest (near zero) when powered by renewables like solar, wind, or hydro.

Q: What are the economic advantages of the new process?

A: Sublime’s process reduces energy costs, generates saleable co-products, and leverages low-value or waste feedstocks—potentially lowering costs while achieving environmental objectives.

The Road Ahead: Challenges and Promise

While Sublime Systems’ process marks a technological breakthrough, widespread adoption depends on broader market, policy, and infrastructure challenges:

Scaling up to global supply: Can new plants meet growing demand quickly enough?
Ensuring reliable, renewable electricity supply at industrial scale
Regulatory acceptance: Ongoing partnership with standards bodies to guarantee universal adoption

However, the promise is clear: decarbonized cement not only enables greener cities but also recasts one of the planet’s most necessary—and polluting—materials as a driver for climate action.

The Sublime Process marks a milestone on the road to sustainable construction, blending science and industry for a carbon-free foundation on which the future can be built.

References

Author

medha deb

Medha Deb is an editor with a master's degree in Applied Linguistics from the University of Hyderabad. She believes that her qualification has helped her develop a deep understanding of language and its application in various contexts.

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