Between a Rock and Hard Place: Commercializing CO2 Through Mineralization

The geosphere refers to the solid materials found within the Earth that contain a vast number of different minerals. Just as a sponge can hold liquid, these minerals can hold huge volumes of carbon. An estimated 2000 times more carbon is stored within the geosphere than in the atmosphere, oceans and biosphere combined. This natural storage bank offers us a solution to permanently hold CO2 through a process known as CO2 mineralization. This process refers to a chemical reaction that occurs when certain minerals are exposed to the CO2, resulting in the CO2 being transformed into rock. Unfortunately, this natural mineralization process is one that typically takes hundreds of years and cannot provide a short-term remedy for our mitigation goals – until now.

In the 1990s, researchers began investigating approaches to the CO2 mineralization process. Today, several solutions exist that provide valuable products such as building materials to serve as alternatives to existing products while also permanently storing CO2 and providing both environmental and economic value.

A brief overview of CO2 mineralization

Concrete curing reaction process (Courtesy of CarbonCure Technologies)

Mineralization comes under the umbrella of carbon capture, utilization and storage (CCUS), which since the 1970s have been dominated by enhanced oil recovery (EOR). EOR is a geological CO2 storage solution involving capturing CO2 from waste gases (or other sources), pumping it down below the Earth’s surface into oil reservoirs, where is it then used to recover more oil from developed oil fields. This solution of storing CO2 as gas underground requires ongoing monitoring for potential leaks.

CO2 mineralization is one of the only options that results in permanent storage of CO2 as a solid, with no need for long term monitoring. Other utilization technologies merely delay the time that the CO2 takes to go back into the atmosphere. For example, CO2-fuel and CO2 for use in fizzy drinks releases the CO2 when the product is consumed.

CO2 mineralization processes fall under three main categories:

Carbonation: CO2 reacts with calcium (Ca) or magnesium (Mg) oxide to form a solid carbonated mineral. The technology is typically retrofitted onto existing industrial/power plants to capture flue gas. These carbonated products can be used in building materials, engineering fill, or specialist construction materials.

Concrete Curing: A similar process to carbonation, but with a focus on producing solid calcium carbonate (CaCO3), replacing energy intensive steam concrete curing methods, resulting in an increased strength. It can also be added to concrete, ready-made concrete when it is mixed, or to precast concrete.  

Novel Cements: CO2 is used as an ingredient within the cement. The CO2 is mineralized within the cement as a solid carbonate, creating a new carbon negative cement.

Making it happen today

CO2 mineralization saw its first wave of financing in the early 2010s. Although a range of CO2 based products were produced, they were not attractive to investors who focused more on technologies with robust, proven business models such as those held by a few CO2 to fuel startups. Today, we are seeing a resurgence of activity for CO2 mineralization driven by new technologies with improved cost performances. In the US, UK and Germany, public funding played an important early role advancing these technologies. Now many have started with small scale demo plants and are moving toward the need for capital to support scaling up to commercial operations.

The COSIA Carbon XPRIZE Challenge was launched in 2015 to find the technologies that convert CO2 into products with the highest net value. The competition has two tracks – one focused on testing technologies at a coal power plant and one focused on testing technologies at a natural gas power plant. The final round began in April 2018, with 27 semi-finalists narrowed down to 10 finalists, each receiving an equal share of $5 million to demonstrate their technologies under real world conditions at a larger scale. In each track, the winner will be awarded a $7.5 million grand prize, announced in March 2020. Five out of the ten companies that have reached the final are focused on CO2 mineralization solutions. We talked with three of those companies using CO2 mineralization with cement.

Carbon Capture Machine (CCM): Carbonation

The Aberdeen-based team spent over a decade in R&D before founding the Carbon Capture Machine in September 2017. CCM captures and converts COinto precipitated calcium carbonate (PCC) and precipitated magnesium carbonate (PMC). A retrofitted system can be attached to any CO2 emitting source using off-the-shelf components to minimize capital costs.

The team currently have a prototype at TRL level 4 that produces 200kg of PCC per day and can be used as a carbon negative replacement for ground calcium carbonate (GCC), a key ingredient of concrete. By replacing GCC, they help to decarbonize the entire concrete industry, which is responsible for 6% of the world’s annual CO2 emissions. While the XPRIZE will help CMM develop a TRL level 6 demo plant, the end game is a fully modularized system that can capture emissions from decentralized point sources.

Although the economic gains are not yet realized, CCM hopes that by reaching commercial scale they can help customers create additional value streams from waste. If they can replicate savings down the value chain to the concrete producer, then their carbon negative product could ultimately replace GCC in the calcium carbonate market, which has a market value of around $20 billion.

Carbon Upcycling UCLA: Novel Cements

CO2NCRETE™ (Courtesy of Carbon Upcycling)

The team’s work began in 2014 and was subsumed into the Carbon Upcycling collaboration, managed by UCLA, with the aim of producing CO2 neutral cement. Their process works like baking a cake: capturing CO2 from flue gas, injecting it into a chemical reaction with other elements, and producing CO2NCRETE™. By utilizing industrial wastes, low-grade heat and CO2, they are able to deliver cost-savings, while eliminating the need for extrinsic processing energy. Furthermore, the process offers the ability to produce cost competitive cemented (carbonated) solids that can be carbon-neutral or better, while achieving functional equivalence to traditional concrete.

The pilot plant produces up to 10 metric tons of CO2NCRETE™ on a daily basis and is at the threshold of TRL 4 maturity. With the help of the XPRIZE, they are looking to develop pilot plants to produce over 100 tons per day, focusing on regions that have ambitious climate goals and progressive environmental regulations. California, with a carbon tax and a mandate for the use of low carbon building materials, is one example of a target market.

Carbon Upcycling is working hard to disrupt the conservative, risk-averse construction industry. If new products are going to compete against traditional methods with over 200 years of testing data, then the economics are going to have to stand up tall to find a place within the $400 billion concrete industry.

CarbonCure Technologies: Concrete Curing

We caught up with to Nova Scotia-based CarbonCure last year when we visited carbon-to-value more broadly. The company has an infrastructure-as-a-service business model, retrofitting concrete plants at zero cost before charging a licensing fee for continual usage. Their closed-loop technology injects recycled CO2 into wet concrete while it’s being mixed, converting the CO2 to calcium carbonate, which increases the end product’s strength. Last time we spoke, the company was planning to use the XPRIZE funds to demonstrate a facility that could utilize onsite waste CO2 for concrete production, as opposed to buying industrial grade CO2 from external customers. They have now achieved this milestone and are looking to replicate this at a coal plant.

CarbonCure is one of the only profitable companies in the space with 100 installations in concrete plants across North America. The company has formed partnerships with key players across the value chain and has recently been taken into the Lafarge Accelerator program.  As a 3x GCT100 company, we believe they are a good example of capitalizing on the opportunities that exist within the Resources & Environment sector.

Like novel cements, concrete curing will have to earn its place in the market before it can be adopted for scale. For some uses such as reinforced concrete, long term durability has to be proven, requiring a testing period of up to 20 years. This doesn’t prevent CarbonCure’s concrete from being used for construction, but for reinforced concrete applications, widespread acceptance of the technology could be delayed until 2030.


In Europe, CCUS still lacks an EU-wide binding target, criteria and budget for financial support. Carbonated materials produced from waste products need to reach the EU End of Waste Regulations requirements in order for products to be sold. Additionally, the EU’s Emissions Trading Scheme market remains in a state of oversupply, with prices sitting at €15/tonne-CO2 today, falling from €30/tonne-CO2 in 2008.

Despite North America’s strong start in the CCUS space, it weakened with the loss of project financing. Government funding was mainly focused more on capture than on re-use technologies. Since 2005, the DOE has invested $7.6 billion in CCS and only $100 million in projects related to the “beneficial reuse” of CO2. The 45Q Tax Credit is positioning the US to drive industrial sector participation through its new credit framework and lowered tonnage threshold for CCUS project eligibility. However, these conditions do not necessarily guarantee success in the market, and if projects do not result in the net-reduction of emissions on a full lifecycle basis, they could fall short of receiving credit.

CO2 mineralization technologies do have the potential to provide meaningful economic and environmental gain; however, many experts believe that CO2 utilization technologies at best could only account for around 12% of current annual emissions. They will need to go hand in hand with other CO2 storage solutions that can also provide standalone economic value.

To keep track of all the latest developments on CCUS and carbon-to-value more broadly, be sure to check out our i3 platform, giving you the latest investment trends in the space.