Using CO2 to create a limestone rock substitute

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A California-based cleantech pioneer – Blue Planet Ltd. – learns from nature to make concrete more sustainable by capturing biomimetic carbon. The company’s economically sustainable carbon capture process creates a limestone rock substitute that can replace aggregate for concrete, dramatically reducing the material’s ultimate environmental impact.

Substitute for limestone for greener concrete

As populations and economies grow in the world, more and more building and infrastructure projects are undertaken each year. This growth has serious consequences for the environment and, in the face of an impending climate catastrophe, ways to reduce this impact are a top priority.

One of the most harmful elements of this continued global development is the widespread use of concrete as a building material. The environmental consequences of concrete are well documented and stem from a variety of factors. Among these is the need for large amounts of rock material for the aggregate – which is ecologically expensive to mine, transport and process.

Blue Planet’s biomimetic carbon capture process creates a limestone substitute that can replace natural limestone quarried (the main ingredient in concrete).

Using a process of carbon mineralization – similar to the natural formation of ooids – Blue Planet produces coarse and fine aggregates from sequestered CO2. The company claims that using this aggregate is the most efficient way to deliver carbon neutral or negative concrete.

Importantly, the limestone rock substitute produced by Blue Planet is equivalent to the limestone mined in terms of strength, performance and cost.

Biomimetic carbon capture: learning from nature

The blue planet’s process for carbon capture is similar to the natural ooid rock formation. Ooids are formed when layers come together around a nucleus in concentric layers. These crystalline layers can be arranged radially, tangentially or randomly around the nucleus, which is typically a shell fragment or a grain of quartz.

Mimicking this natural ooid formation, Blue Planet introduces CO2 captured combustion gases to a water-based capture solution. This process results in a carbonate solution which is coated onto a core or substrate. The coating is described as synthetic limestone (CaCO3).

The carbonate mineral coating is composed of 44% captured CO2 so that each tonne of the final Blue Planet product represents 440 kilograms of carbon dioxide sequestered from the atmosphere.

CO captured2 the coating is then exposed to a recycled aggregate material which contains sufficient alkalinity. Common rock waste or industrial waste is recycled for this purpose to further increase the positive environmental impact of the final material.

When the carbonate solution is exposed to the alkaline aggregate substrate, the metal ions present in the aggregate, such as calcium, magnesium and iron, are recharged. This reaction causes the metal ions to break free and combine with the carbonate solution to form a mineral coating – much the same way ooid rocks are formed.

Because there is no purification step required for Blue Planet’s biomimetic carbon capture – unlike other carbon sequestration methods – it sequesters carbon more efficiently. Purification is both an energy intensive and capital intensive process, so removing this step results in more economically sustainable carbon capture that also uses much less energy.

Creating Concrete Aggregates From Thin Air: Introducing Blue Planet

Video credit: Healthy Climate Alliance /

Blue Planet Limestone Rock Substitute Applications

The economically sustainable carbon capture product described here replaces the natural limestone that must be extracted from quarries to meet the ever increasing global demand for concrete.

Blue Planet factories can produce aggregates of various sizes, from fine sand-like materials to coarse gravel. In addition, these aggregates trap atmospheric carbon in their carbonate coating, preventing it from entering the atmosphere or hydrosphere.

Already, development projects are using this material to ensure longer lasting results without compromising performance or costs. For example, San Francisco International Airport in California recently used Blue Planet’s limestone substitute to complete a major development project with integrated and economically sustainable carbon capture. This significantly reduced the overall carbon footprint of the project.

Carbon sequestration technologies like this are an important part of our collective effort to reduce the number of harmful COs.2 in the atmosphere and hydrosphere. By working to develop an economically sustainable carbon capture process, Blue Planet contributes to the global CO challenge2 reduction significantly.

References and further reading

“Economically sustainable carbon capture.” Blue planet. [Online]

Matter, Juerg, M. et al. (2016). “Rapid carbon mineralization for the permanent elimination of anthropogenic carbon dioxide emissions.” Science. [Online]

Russo, ME, Olivieri, G., Salatino, P. and A. Marzocchella (2013). “CO2 capture by biomimetic adsorption: enzymatically mediated CO2 uptake for the process of carbon sequestration and storage after combustion.” Journal of Environmental Engineering and Management. [Online]

Wang, Yin, Shiying Lin and Yoshizo Suzuki (2007). “Study of calcination of limestone with capture of CO2: decomposition behavior in a CO2 atmosphere.” Energy fuels. [Online]

Disclaimer: The views expressed here are those of the author, expressed in a private capacity and do not necessarily represent the views of Limited T / A AZoNetwork, the owner and operator of this website. This disclaimer is part of the terms and conditions of use of this website.

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