Green Technology

Sublime Systems Can Help Clean Up Carbon Emissions From Cement

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At CleanTechnica, we tend to focus on the EV revolution because emissions from cars and trucks account for about 30% of carbon emissions globally. Reducing those emissions is obviously vital to addressing the climate emergency we have created for ourselves. But while that is true, it also means about 70% of those emissions come from other sources. Cement is one of the largest.

According to Canary Media, cement is responsible for more carbon emissions each year than those attributable to any nation on Earth except China and the US. Each year, almost a cubic mile of cement is produced worldwide each year. While cement companies are hard at work trying to reduce the amount of carbon emissions from the industry, the fundamentals of making cement — especially Portland cement — are subject to the laws of science.

The core input of ordinary Portland cement — which makes up the vast majority of cement produced today — is limestone, a mineral that’s about half calcium and half carbon and oxygen by chemical composition. When that limestone is converted to calcium oxide, the immediate precursor to the clinker that is transformed into cement, the CO2 trapped inside the mineral is released into the atmosphere.

Eliminating these emissions means either finding novel, emissions-free ways to create ordinary Portland cement or a safe structural equivalent, or figuring out how to economically use carbon capture, utilization, and sequestration (CCUS) technology to keep the CO2 generated from the manufacturing process from entering the atmosphere. Though plenty of startups, companies and researchers are hard at work on both methods, neither has, at this point, proven to be workable at the necessary scale, Canary Media says.

Holcim cement

Image courtesy of Holcim

Switzerland’s Holcim is one of the world’s largest producers of cement in the world. In its latest financial report, it says it has reduced its carbon emissions by 21% compared to the prior year, largely by using different aggregates that get mixed with the cement to make concrete. But the basic process of making cement is much more difficult to decarbonize.

Holcim this week announced a $100 million investment in a factory in the US that will produce 600,000 tons of cement a year while eliminating 400,000 tons a year of carbon emissions. That’s progress, especially because the company says the money it saves is actually more than it spends on emissions reduction strategies.

Sublime Cement Achieves 90% Reduction

We have reported previously on Sublime Systems, an MIT spinoff that is working to decarbonize the production of cement. (The name is a subtle pun that only organic chemistry majors will get.) In September, the company announced its low carbon, scalable, and drop-in replacement for traditional cement in concrete has obtained the ASTM C1157 designation.

Meeting that standard means Sublime cement can be used to make concrete that meets or exceeds applicable US and international building codes, unlocking a path for it to replace ordinary Portland cement at scale to massively lower the carbon output of the global construction infrastructure.

That was a major milestone for Sublime. No one would specify its product if it didn’t meet the ASTM standard. But strength and durability of the end product are not related to the carbon emissions produced when making the product. For that, additional testing was necessary.

This week, Sublime told CleanTechnica via email the additional testing has been completed. Climate Earth, the leading provider of environmental product declarations (EPDs) for the concrete industry, conducted a lifetime climate assessment (LCA) according to a widely accepted industry method, avoiding controversial and unproven offset methodologies frequently used to enable the continued burning of fossil fuels such as carbon capture, forestry credits, co-product mineralization, and lifetime CO2 absorption.

The cradle-to-gate screening LCA leverages engineering estimates of Sublime Systems’ full scale commercial manufacturing process and was conducted in conformance with ISO 21930. The testing by Climate Earth validated that the Sublime Systems process can eliminate more than 90% of the global warming potential (GWP) of cement manufacturing, when compared to today’s ordinary Portland cement (OPC).

“The ground rules are changing, and we see industry disruption for how we do design and specify buildings. With EPDs at the center of low carbon building material validations, the suppliers who are first to adopt EPDs are seeing doors open and unprecedented access to developers and specifiers,” says Don Davies, a professional engineer who is an advisor to Sublime Systems and chairs the non-profit organization Building Transparency.

Verifying A 90% Reduction In Carbon Dioxide

The testing found that the Sublime Systems manufacturing process resulted in a GWP of 72 kg CO2/ton for a 100% Sublime Cement blend, compared to the 922 kg CO2/ton GWP found in the EPD for industry-wide average OPC in the United States. The remaining emissions were largely related to the mining and transportation of feed stocks, waste, and wastewater treatment, processes that are primarily upstream and downstream of the company’s core manufacturing innovations.

The LCA testing also showed drastically reduced acidification and eutrophication potentials (among others) without increased water consumption, reflecting a lower environmental footprint and permitting timeline compared to today’s OPC.

“As our company developed this breakthrough process, we were mindful that the construction industry wouldn’t respond well to shining white knights with splashy in-house PowerPoints claiming they’re saving the world,” said Sublime Systems CEO and co-founder, Leah Ellis. “Seeing is believing, and we are grateful to be partnering with Climate Earth, the leader in these critical analyses for the concrete industry. Apples-to-apples comparisons using rigorous industry-accepted standards are foundational to driving real climate solutions and giving our stakeholders confidence in Sublime Cement as a powerful decarbonization tool in their arsenal.”

Sublime Creates Cement Without Fossil Fuels Or Carbon Capture

Sublime Systems is advancing a fully electrified process for manufacturing cement without requiring the use of fossil fuels or limestone. This carbon-avoidance approach harnesses clean, renewable sources of electricity and a wide range of calcium bearing raw materials to produce the same final hardened phase in concrete that the global construction industry requires today. Sublime Cement does not rely on carbon capture and storage infrastructure to reduce CO2 emissions, enabling cost parity with OPC when produced at scale without dependence on carbon credits or carbon penalties.

“Sublime has shown incredible rigor in specifying their manufacturing process, enabling our team to confidently quantify the environmental impact of their electrochemical cement manufacturing process,” said Climate Earth CEO Chris Erickson. “We are excited to continue working with the company on future EPDs that will help accelerate industry adoption of Sublime Cement as a next-generation, low carbon building material of the future.”

Sublime Systems is currently engaging with its construction industry partners for its first major construction projects this quarter and is actively planning its first commercial facility, which will produce tens of thousands of metric tons of low-carbon cement per year. Sublime Cement functions as a fully drop-in replacement for OPC in concrete today and complies with ASTM C1157, a widely adopted fully performance-based industry specification for hydraulic cement.

The Takeaway

The critical component here is cost. Everyone wants to save the Earth, but not if it hurts the bottom line. As Canary Media points out, profit margins in the concrete business are slim. That’s why it’s so important that Sublime Cement is cost competitive with conventional cement products, especially original Portland cement.

Anytime you read about how carbon capture is going to solve all our problems, remember this. It’s expensive, which will make the price of products that rely on it uncompetitive. In addition, it just flat out has never been proven to work.

The real victory will come when giant companies like Holcim switch over to Sublime Cement for their concrete products. That’s when we will know that real progress toward decarbonizing cement and concrete has been made. After that comes transporting all that cement and concrete in battery electric trucks. Hey, we can dream, can’t we?


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