The steel industry produces massive quantities of waste materials with no or at best low-value applications, creating serious environmental issues. On the other hand, the construction industry is responsible for a large amount of global CO2 emissions and drastically needs to improve its environmental impact. To address these two problems, EARTO member VITO developed the Carbstone process that transforms waste materials and CO2 into high value construction materials with drastically reduced environmental impact. During this development, VITO collaborated closely with the company ORBIX.

In the steel industry, massive quantities of alkaline waste materials such as steel slags or construction and demolition waste are produced each year. For instance, 170-250 million tonnes of steel slags were produced worldwide in 2014. Besides, in the construction industry, concrete assumes an eminent role with a production of 30-35 bn tonnes/year, making it the second-most used material by mankind behind water, while concrete manufacturing is responsible for up to 8% of global CO2 emissions. A better and more efficient processing of alkaline waste and CO2 into high value products therefore provides large environmental benefits.

Breakthrough technology

VITO’s Carbstone process transforms alkaline waste and CO2 into high value construction materials. The process uniquely combines existing technologies, using accelerated mineral carbonation by treating various types of waste with CO2 at elevated pressure and temperature. The CO2 is sequestered inside the products by transforming CO2 gas into solid carbonate minerals that cement the slag particles together. This flexible technology allows for the production of a range of products, from paving bricks to roofing tiles, with the same technical properties as conventional concrete products.

Reduced environmental impact

Carbstone’s considerable environmental benefits turn this technology into a disruptive innovation. Indeed, Carbstones have a negative CO2 footprint, 200kg CO2/kg lower than conventional concrete construction products, mainly due to a highly energy-efficient production process and the incorporation of CO2 inside the materials. CO2 emissions are also avoided by a decreased use of primary raw materials. Besides, around 800kg of secondary raw materials can be recycled to produce a tonne of Carbstone material, an extremely high ratio compared to the 28% substitution rate of current concrete based construction materials. Carbstones therefore avoid landfilling, save on primary raw materials and reduce global warming.

From pilot to market

For the development of the Carbstone process, VITO collaborated closely with the company ORBIX. To further develop this patented technology, a pilot plant was created in 2014 and large-scale industrial trials are conducted. The target is to set up a production plant for the Belgian market in 2017, while developing a licensing model to commercialise the technology worldwide. The market targeted by Carbstone is estimated to grow by 1.2%/year, reaching 16bn tonnes by 2050. The "breakthrough scenario" estimates a production of 50m tonnes of Carbstone by 2040, while recycling 40m tonnes of waste and saving 10m tonnes of CO2, with a total investment of €335m and 17.500 full-time jobs created.  An important step towards market introduction was recently made by licencing the technology to De RuwBouw Groep (CRH). De RuwBouw Groep has the ambition to implement the Carbstone technology worldwide for the production of construction materials (bricks). The first products will we released on the market in the Netherlands early 2017 under the trade name: Compensatiesteen.

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