Neustark launches a new product for slurry water (residual water)…

The invention solves an old problem in concrete production by enabling the neutralization of the residual water, thereby reducing disposal costs. Read on to find out more about the potential of the circular economy in concrete production.

The new slurry plants from neustark continuously neutralize residual water by adding biogenic CO₂
The extended residual water treatment can reduce disposal costs and permanently bind CO₂
The financial compensation for the permanent CO₂ storage leads to additional income for concrete recyclers operating in the construction industry

Every concrete recycling plant faces the same problem. The residual water, also called slurry, is produced when stationary concrete mixers, mixing containers, and equipment are cleaned. As slurry water has a highly alkaline pH value of 10-14, it must undergo extensive treatment before it can be discharged into the sewage system or reused in concrete production.

The conventional process: The slurry water in the tank is usually neutralized twice a year during inspection by adding acid or carbon dioxide. The advantage of the CO₂ treatment is that it prevents the pH value from dropping too low, even in cases of excessive dosing. However, CO₂, usually produced industrially, is more expensive than acid.

The process supplemented by neustark’s technology: The slurry plants were specially designed to treat residual water with CO₂.

And this is how it works:

1) A pump draws water from the tank 2) Gaseous CO₂ is then added 3) The tech makes the gas-liquid mixture react in the static mixer 4) A tank collects the remaining CO₂, enabling the CO₂ flow to be regulated 5) Water and solids circulate through the system in several cycles until the maximum amount of CO₂ is absorbed. At the same time, the residual (slurry) is neutralized.

Advantages of the neustark plant

As with the existing process of using CO₂, a chemical reaction occurs between the CO₂ and the cement phases in the residual water. The CO₂ transforms into limestone through a mineralization process and is bound for hundreds of thousands of years. The pH level is lowered to a point where excess residual water can be safely discharged into the sewage system at minimal disposal costs or reused in the production of fresh concrete.

So, what are the specific advantages of the neustark plant?

The slurry water treatment process is not interrupted by our plant but integrated into an existing process. In addition, neutralization can be carried out continuously instead of a few times a year.
Industrial CO₂ is expensive, while the CO₂ neustark uses, comes from biogas plants and is cheaper.
Our solution makes the process of CO₂ storage in residual water measurable. Thanks to our flow meters, we know exactly how many tons of CO₂ are stored.
The neustark plant contributes to climate protection: The CO₂ used is of biogenic origin. By converting it into limestone, we have permanently removed it and thus created so-called negative emissions.
For every ton of CO₂ stored, the operator of the concrete plant receives a fixed compensation from neustark. Depending on the residual water quantity, a plant can store between 50 and 250 tons of CO₂ per year.

The neustark slurry water plant for CO₂ storage in residual water.

With a weight of less than 500 kg and compact dimensions that fit on a europallet, the plant can be easily delivered and quickly installed.

In addition to the financial compensation for the stored CO₂, the concrete plant recycler has less work to do, as the plant automatically stores CO₂ in the residual water 1-2 times a day. Also, the steady supply of CO₂ is taken over by neustark.

Conclusion: Less time and effort, more returns, real climate protection

The neustark slurry water plant solves a well-known problem in concrete production and turns it into a source of additional revenue. Seamless integration into the existing process and the ongoing neutralization of the residual water simplifies work and reduces disposal costs. At the same time, the plant actively contributes to climate protection through biogenic CO₂ storage. Thanks to the precise measurability of the bound CO₂, the recycler receives compensation for every ton stored – a simple and sustainable way to protect the environment and benefit economically.

FAQs

In addition to the storage of CO₂, the mineralization process simultaneously neutralizes the slurry. This means that excess residual water can be fed into the wastewater without high disposal costs.
Depending on the density of cement parts in the residual water and the amount of residual water produced, our plants can store up to an additional 200 tons of CO₂ every year.
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.