Carbonation – carbon dioxide storage that creates value

To reduce the amount of carbon dioxide in the atmosphere and meet the goal of limiting global warming to 1.5 °C, considerable resources are now being invested in finding new methods for carbon capture and sequestration (CCS). Traditional CCS involves the separation of carbon dioxide from emission sources, including its transport to and storage in geological formations. There is demand for simpler and cheaper alternatives to the permanent sequestration of carbon dioxide under the seabed. In recent years, industry has begun to recognise the value of carbonation, a technology that can both capture and store carbon dioxide locally. In addition, products are created, such as precipitated calcium carbonate, which can be sold or used in other processes. By utilising a natural process, there are great opportunities to convert residual products into different types of resources while, at the same time, the use of carbon dioxide creates carbon sinks.

Major interest from industry

A few years ago, RISE’s Infrastructure and Concrete unit started researching carbonation-based CCS. And interest from industry has increased steadily.

– “We work to develop various technologies for carbon dioxide capture and storage, including carbonation,” explains Placid Atongka Tchoffor from RISE, who conducts research in the field. “We also develop suitable materials that can separate carbon dioxide from various flue gases. This type of technology has massive potential to help the world achieve its climate goals.”

Natural process

Carbonation (in this sense: carbon sequestration by mineral carbonation) is a natural process through which carbon dioxide reacts with calcium and magnesium. The phenomenon is usually associated with cement, but the process can be used for many different materials. The method essentially involves using a suitable leaching agent to extract calcium and magnesium from residues containing high levels of these substances, such as slag or ash. The carbon dioxide helps to convert calcium and magnesium into calcium carbonate or magnesium carbonate in solid form. The carbonated materials or pure carbonates can then be used as bulking agents in concrete or as fillers in paint products or pulp and paper products.

Secure storage method

Another advantage is that the method is significantly safer than other forms of sequestration. Carbonated products are thermodynamically stable at normal temperatures and can be left outside at no risk of further reaction.

Research must contribute to achieving climate goals

The research within RISE focuses on developing cost-effective carbonation processes with these residual products for various applications so as to contribute to achieving Sweden’s climate goals in a decentralised way.

– “Our ambition is to develop value chains where carbon dioxide emitters, producers of alkali-containing residual products, and end-users of carbonation products contribute and benefit from carbonation-based CCS,” says Placid Atongka Tchoffor.  “This enables costs for carbonation to be shared among several operators, which will make carbon dioxide capture and storage more economically viable.”

Cost is crucial

Globally, the potential exists to capture and store approximately 100,000 gigatonnes of carbon dioxide by means of carbonation. Tchoffor has seen that one of the obstacles to further developing CCS has been the large costs involved. If it can be made cheaper while also generating secondary gains for the industry, the method could have a wide impact.

– “We want to use waste materials from industry that cost money to dispose of,” says Tchoffor. “If it can instead be used as a raw material in this process, it creates new opportunities. It requires creating a value chain with different operators who benefit from carbon dioxide capture and storage through carbonation. If the costs can be shared between different operators, CCS can become profitable for the industry and benefit the environment.”

Residual products become a resource

Lidköping Energi is a company interested in carbonation. At present, it costs them around SEK 1,000 per tonne to dispose of fly ash from the conversion of waste and biomass. But through a project they are running together with RISE, they see that the ash can instead be used to capture carbon dioxide, and at the same time produce a material that can be sold or used in different ways.

Availability of materials a challenge

For companies looking to test carbonation, it is important that possibilities exist to make use of the products from the carbonation process. It is a great advantage if a value chain can be created comprising different operators where everyone benefits. A major challenge is also finding materials that can be carbonated, since availability is not a given in every city in Sweden.

– “The largest volumes come from the mining industry in the form of tailings, which are mostly disposed of,” says Tchoffor. “There is interest in using this for carbonation, but the logistics are problematic since the mines are located in northern Sweden. The material must be transported as most emitters are in southern Sweden.”

RISE is developing methods for carbon dioxide separation in which carbonation can also be used as a separation process for gases from industry.

– “What makes carbonation interesting is that you separate and sequester at the same time. If you take another type of material, for example, amines, they only help to separate and cannot store carbon dioxide,” says Placid Atongka Tchoffor.