The science behind our solution: CO₂ storage through mineralization

Name: neustark
Price range: $

We use mineralization to durably store CO₂ in mineral waste streams - a 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 unavoided emissions from the atmosphere?

Neustark has developed a solution to do exactly so: by capturing then mineralizing CO₂ in demolished concrete. This process works as an add-on to concrete’s normal recycling process. The CO₂ is stored permanently – 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

This is how it works

Source

To source the CO₂, we work with biogas plants that separate CO₂ from methane through a process called biogas upgrading. With our technology installed at the plant, neustark captures and liquefies the vastly pure 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 concrete granules.

Store

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

Remove

Et voilà, the CO₂ is stored – permanently, i.e. the risk of reversal is slim to none. We’ve removed CO₂ that would otherwise be released in the atmosphere. And since the CO₂ we captured is of biogenic nature, we create negative emissions

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

Certificate

We help businesses achieve their climate goals by removing their unavoided 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 certified carbon removal (CDR).

Neustark creates negative emissions by storing CO₂ in demolished concrete, the largest waste stream in the world.

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 various 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 demolition concrete?

Permanence

The mineralization process in concrete permanently stores the CO₂. The risk of reversal is proven to be slim to none, and the CO₂ is stored for thousands to millions of years.

Gigaton potential

Demolished concrete is the world’s largest waste stream. It’s an existing material, which offers a storage potential of numerous gigatonnes per year.

Easy to scale

We work with concrete recyclers alongside their existing processes. The industry is already in place, and we add on our technology without disturbing the status quo.

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?

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The science behind our solution: CO2 storage through mineralization