The science behind our solution: permanent CO₂ storage via surface mineralization

Name: neustark
Price range: $

We use mineralization to durably store CO₂ in mineral waste streams – a local and scalable solution for long-term climate impact.

With over 1 billion tonnes per year, demolition concrete is the world's single largest waste stream. So what about turning this waste stream into a ‘sink’ that absorbs hard-to-avoid emissions from the atmosphere?

Neustark has developed a solution to do exactly that: by capturing then mineralizing CO₂ in mineral waste such demolished concrete, slags and bottom ash. This process works as an add-on to the materials' normal recycling process. The CO₂ is stored permanently in the aggregate – and thus removed from the atmosphere.

We’re turning demolition waste into a carbon sink.

Neustark stores around 10kg of CO₂ per tonne of demolished concrete. One site can do in one hour what 50 trees do in one year.

Learn more about our impact

What is CO₂ mineralization?

CO₂ mineralization, also called carbonation, is nature’s way of sequestering carbon dioxide in rock. Over time, CO₂ reacts with calcium or magnesium-rich minerals, forming solid carbonates like limestone (CaCO₃) or dolomite (MgCO₃).

This natural process, which normally takes millennia, can be accelerated to just a few minutes. Mineral-based materials such as industrial waste react with CO₂ to form carbonated products like recycled concrete aggregate (RCA) where it is durably bound.

The best part? The mineralization process is easily integrated in existing industrial infrastructure. And the resulting materials, e.g. cRCA, meet the technical requirements to use in road or building construction.

This is how it works

Source

To source the CO₂, we work with wastewater facilities and biogas plants that separate CO₂ from methane through a process called biogas upgrading. With our technology installed on site, neustark captures and liquefies the vastly pure and biogenic CO₂ offgas.

Transport

We then transport it to nearby sites where we sink the CO₂. We partner with construction recyclers to harbor our mineralization technology at their plants, where we inject the CO₂ into finely crushed demolition aggregate.

Store

Through the accelerated mineralization process that our technology triggers, the CO₂ then turns into limestone and is bound to the granules’ pores and surface. This happens alongside the recycler’s existing value chain of processing demolition waste to re-use to build streets or produce recycled concrete.

Remove

Et voilà, the CO₂ is stored – permanently, i.e. the risk of reversal is slim to none. Since the CO₂ we capture and store is of biogenic nature, we create negative emissions. We remove CO₂ that would otherwise be released in the atmosphere.

How neustark measures, reports and verifies (MRV) our climate impact and our CDR

Certificate

We help businesses achieve their climate goals by removing their unavoidable CO₂ emissions. More and more organizations are embedding carbon removal, next to their reduction efforts, in their climate strategies. They partner with neustark to acquire local, highly permanent, measurable and certified carbon removal (CDR).

Neustark creates negative emissions by permanently storing CO₂ in mineral waste.

Neustark’s role

Neustark was the first to show that this value chain is both ecologically and commercially viable. And the first to deploy its solution at no numerous sites across Europe – already removing CO₂ today, and even more tomorrow.

By broadly deploying our proven solution, we can reduce the operational costs and thus decrease the price for carbon removal – and significantly increase the amount of CO₂ we store.

So why store CO₂ in mineral waste?

Highest permanence

Mineralizing the CO₂ in demolition aggregate permanently binds it. The risk of reversal is proven to be slim to none, and the CO₂ is stored for thousands to millions of years.

Scalability

Mineral waste such as demolished concrete, slags and bottom ash make up the world’s largest waste stream. Existing material that offers a storage potential of numerous gigatonnes per year.

Integrated in local industry

We work with local biogas producers and demolition waste recyclers to integrate our solution into their existing processes: it's a value add for all partners, and ultimately, for our planet.

FAQs

Currently we can store around 10 kg of CO₂ per ton of demolition concrete on an industrial and economical basis – and we’re continuously working on optimizing this figure. Depending on the material characteristics, we can store up to 25 kg of CO₂ per ton.

In terms of speed, our latest plant stores around 1000 kg of CO₂ per hour in concrete granulate. As a comparison: fast-growing pine trees absorb about 20kg of CO₂ per year. So one neustark plant can do in one hour what 50 trees need a whole year for.

Or, in other words, within 24 hours, one neustark plant can store the same amount of CO₂ in demolished concrete granulate as the CO₂ that is on average emitted by two single-family homes heating with oil in Switzerland in a year’s time.

For more information, please see Johannes Tiefenthaler et al’s Technological Demonstration and Life Cycle Assessment of a Negative Emission Value Chain in the Swiss Concrete Sector.
No. The mineralization process that is the core of neustark’s technology enables durable CO₂ storage. Permanent means: it is scientifically proven that the fraction of carbon dioxide stored through mineral carbonation that is retained after 1000 years is virtually certain to be 100%. Even if the concrete in which the CO₂ is injected gets demolished again and again, the CO₂ will not be released into the atmosphere.

There are many negative emission technologies that are in theory, and an increasing amount in practice, viable. They all certainly have their benefits, but mineralization is one of the few technologies that warrants true permanent carbon removal.
Carbon dioxide mineralization is a process in which CO₂ reacts with alkaline metal to form solid carbonate minerals.

Demolished concrete aggregate contains hydrated cement phases. These hydrated cement phases are in contact with water, e.g. pore water – and thus in a solid-liquid equilibrium. Part of the hydrated cement is dissolved in the water and therefore present as ions. As CO₂ is also dissolved in this water, new mineral that exhibit lower solubility than the hydrated cement phases precipitate. And voilà, calcium carbonate (CACO₃) is formed.

Thus, the CO₂ and the hydrated cement undergo a chemical transformation to form rock. This so-called carbonation reaction of 1 kg CO₂ releases heat such that the temperature of 1,000 kg of concrete increases by about 2.5°C.

CACO₃ is considered to be amongst the most permanent ways to sequester carbon. Only temperatures above 600°C or very strong acids could trigger the release of CO₂. This ensures that the CO₂ remains stored in the concrete, even if it is demolished again after being reused.
We partner with biogas plant to filter out the CO₂ that is created during the plant’s production process. We then liquefy the captured CO₂ to then transport it to the nearby storage sites.
The CO₂ that we source is biogenic. Biogenic carbon emissions are those that originate from the processing (e.g. combustion, fermentation) of biological materials such as plants and trees. Burning biomass emits carbon that is part of the biogenic carbon cycle (as compared to burning fossil fuels, which releases carbon that has been locked up in the ground for millions of years). In other words, biomass combustion simply returns to the atmosphere the carbon that was absorbed as the plants grew.

When neustark’s technology injects CO₂ into concrete, it is permanently stored there and removed from where it would otherwise land, in the atmosphere. And since the CO₂ is biogenic, this sequestering process generates negative emissions.

Neustark’s first source partner is the biogas plant ARA Region Bern in Switzerland. New source sites are currently being built, and further partnerships being evaluated, to ensure a close proximity of our source and storage sites.
Neustark’s research & development team is working on optimizing our current technology as well as potential future solutions of permanently storing CO₂.

We are testing various materials and optimizing our technology operations to increase the average intake of 10kg of CO₂ per ton of demolished concrete.

We are also investigating other related paths of storing CO₂, e.g. in concrete residual water or concrete slurry, and other waste materials.

On a more long-scale time scope, we are delving into the possibilities of storing CO₂ geologically. Neustark is a leading partner in the research project DemoUpCARMA, led by ETH Zurich, which explores the technical, political and economic scope of storing Swiss CO₂ geologically in Iceland.

Want to know more about the impact we generate and how we measure it?

Explore our numbers

The science behind our solution: permanent CO2 storage via surface mineralization

What is CO2 mineralization?