CCUS - Carbon Capture as a possible solution to climate neutrality?

Innovative technologies aims to combat climate change through CO2 capture

CO2 capture
Source & Copyright by Freepik Macrovector

Author: Lara-Sophie Buckow

Today, significantly more CO2 is produced than is naturally broken down. The burning of coal, crude oil and natural gas for energy production accounts for a large share. At the same time there is a massive clearing of forests and waters dry up. As a result, the natural breakdown of carbon dioxide is no longer possible to the same extent as before.

Carbon Capture offers an innovative solution to the problem. The capture of CO2 when burning fossil fuels and underground storage should make it possible, according to scientists, to keep around 65 to 80 percent of the CO2 permanently out of the atmosphere. You can find out what exactly is behind it here.

CCUS: CO2 capture as an innovative solution?

Since many things in our everyday life are hard to imagine life without, or rather such a dramatic change in our way of life is unrealistic, business and industry rely on CO2 capture measures. The greenhouse gas is collected from the air or directly during production, for example during the burning of coal, and then either stored in storage or used as a component of new products and services. This process is called carbon capture, utilization and storage (CCUS or CCS).

It is no coincidence that the XPrize, a prize supported by Elon Musk and endowed with 20 million US dollars, was launched in 2015 to boost the carbontech economy. The winners were announced just this year and are Canada's Carboncure, which extracts and recycles CO2 produced during concrete manufacturing, and UCLA's Carbonbuilt, which developed a system that absorbs CO2 and creates a cement alternative that relies less on environmentally damaging Portland cement.

 CO2 capture Xprize CCUS

Source & Copyright Carboncure

What exactly is CCUS?

These processes have been around since the 1970s, but on a larger scale only since the 1990s. With the increase in greenhouse gases, CO2 capture is gaining more and more attention, as natural resources can no longer sufficiently absorb the CO2 in the atmosphere. There are various methods of capturing the carbon dioxide and using it accordingly. Here are the most important technologies:

Overview Carbon Capture CCUS Process

Process by CCUS, Source & Copyright by iea

1. Chemical absorption:

This technology of chemical absorption has been in use for a long time and represents a relatively uncomplicated way of CO2 capture. The reaction of CO2 with a chemical solvent separates the carbon dioxide from the air. This enables the production of pure CO2.

2. Physical separation:

The physical separation is currently mainly used in gas processing. The CO2 is separated from the other constituents in the air by a surface or a liquid and finally with heat or pressure.

3. Oxy-fuel separation:

This technology is still in the test phase and is mainly used for energy generation from coal and cement production. The fuel is burnt by nearly 100% oxygen as well as the resulting CO2 is captured.

4. Membrane separation:

This technology is also not yet widespread. It is based on membranes, i.e. polymer or inorganic devices, which separate the air into its individual components. In this way, carbon dioxide is separated from the other gases and collected.

5. Calcium looping:

This method takes place through two consecutive processes. Within the first, calcium oxide, i.e. burnt lime, separates the CO2 from other gases and forms it into calcium carbonate. In the second step, the calcium carbonate is separated again into its individual pieces: burnt lime, which is reused for the first step, and pure carbon dioxide.

6. Chemical looping:

Here, too, the process is divided into two steps. First, pieces of metal bind oxygen to themselves. The resulting metal oxide is combined with fuel in the second step. The resulting reaction produces energy as well as pure CO2. The metal is reused for the first step.

Transport options via pipeline, ship or truck

The transport of CO2 is relatively simple. Like oil or other gases, the transport for longer distances and quantities can take place by pipeline or as cargo by boat. Especially in North America, the use of pipelines on land for CO2 transport is already ubiquitous. In the future, the network for this and the initialisation of so-called CO2 capture hubs is to be further expanded.

While pipelines can transport large quantities of CO2 safely and quickly over long distances, they are inflexible and expensive if they are only installed for small quantities. Transport by truck or boat, although more expensive, is much more flexible. With the hubs and local transport, it would therefore be possible for smaller regions to operate carbon capture independently and eventually transport it from the hubs, centred and collected, by pipeline to CO2 storage facilities.

Versatile use of CO2 possible

Once the CO2 has been collected, it is time for further use. There are already numerous methods for using carbon dioxide in different industries. A distinction is made here between two processes in particular: Conversion and Non-conversion. In the former, the CO2 is transformed through chemical and biological changes so that it serves as a raw material in another form. In non-conversion use, the CO2 is used in its original form.

List of possible uses of CO2 Capture CCUS

Uses of CO2, Source & Copyright by iea

CO2 is probably best known in the form of dry ice for the storage of perishable food and for special effects. However, it can also be used to produce urea, which is used in cosmetic products and as a nitrogen fertiliser in agriculture or as a method of reducing nitrogen oxides.

The industry also finds use for CO2 in other forms. Innovations continue to be made in the areas of conversion into fuels, as an alternative product in the production of chemicals, and as a building material. With the expansion of research and development of CO2 use, progress is steadily increasing.

Storage options are associated with risks

Despite the versatile use of CO2, the storage of excess carbon dioxide is still necessary. This is possible above all in underground storage facilities. Usually from 800 metres underground, these reservoirs are ideally suited for the safe storage of the gas due to several layers. The largest capacities are currently offered by saltstone caves or exhausted gas and oil reservoirs. Further storage methods are already in the test phase. Globally, according to the International Energy Agency (IEA), there is sufficient storage capacity available for CO2.

According to the Federal Environment Agencythe additional energy required for separation, transport and storage is particularly problematic. The storage of CO2 can only make an effective contribution to combating climate change if the stored CO2 remains permanently and completely in the storage facilities. This requirement is also set by the Carbon Dioxide Storage Act. Health risks can arise as a result of accidents at the underground facilities, such as leakage of CO2, or through a gradual release from the storage complex. Above-ground facilities pose concerns with regard to impacts on flora, fauna and biodiversity.

Conclusion: CO2 capture as a controversial hope

The effects of increased levels of CO2 are omnipresent. Extreme weather events no longer occur sporadically per century, but are a regular occurrence. Climate change is no longer deniable and it is urgent time to do something about it. This can only be achieved by reducing CO2 as a by-product as much as possible and capturing the gas left over after natural absorption. The various methods of carbon capture and storage represent a controversial solution so far. Methods of further utilisation can be seen as a ray of hope, but they are still far from being perfected for use on a larger scale.

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