WHAT IS CARBON CAPTURING (CCS) part 1

WHAT IS CARBON CAPTURING?

The emission of carbon oxides from many industrial processes has become  a major concern. It is estimated that, in 2019, the United States emitted 5.1 billion metric tons of energy-related carbon dioxide, while the global emissions of energy-related carbon dioxide totaled 33.1 billion metric tons.

This was based on findings from the U.S. Energy Information Administration. In bid to curb the amount of waste gases present in the atmosphere, World institutions have put in no small effort. One of the major solutions is Carbon capturing and Storage (CCS).

Carbon capturing and sequestration is the process through which carbon oxides are collected and stored far beneath the ground in geological formations. While the carbon IV oxide in the air could also be collected, it is by no means cost effective.

The concentration of Carbon IV oxide in air compared to that from industries is highly negligible and so, the prospects are low. Collection from point sources such as industries with large fossil and synthetic fuel consumption has proven to be beneficial and successful.

In fact, existing power plant arrangements can still have the sequestration facilities installed.

HOW CCS WORKS

Most engines and power plants make use of carbon fuels to generate power. The gaseous products of this process contains a high concentration of Carbon IV oxide (CO₂) and Carbon II Oxide (CO).

These gases are mostly released into the atmosphere where they cause damage to the atmosphere. CCS works to limit, if not eliminate, the emission of these carbon gases by injecting it into the earth.

There are 2 phases to the process: collection, transport and storage. Let’s look at them individually.

COLLECTION

The collecting of carbon gases is carried out through a variety of means, the major of which are:

1. Absorption/Carbon scrubbing: This makes use of a carbon scrubber or amine such as Monoethanolamine to absorb the gases. The gas is then collected for storage and the carbon scrubber is reused.
2. Adsorption: Here, a Metal-Organic framework (MOF) is used to attach the CO₂ molecules to its surface. This process might demand that the gas molecules and the metal surface react, though this is not always the case. Using Temperature or Pressure Swing Adsorption, the carbon gas is separated and the MOF is reused.
3. Chemical Looping: Here, metal oxide particles are mixed with fuel of any state, liquid, solid or gas, and alloeed to react in a fluidized bed combustor. The products of this reaction are solid metal particles, CO₂ and water vapour. The water vapour is condensed while CO₂ is carted away. The metal particles are taken off to another fluidized bed where they react with air to form oxides again. The process is then repeated.

Carbon can also be collected before combustion, after combustion or through a process called Oxy-fuel combustion. In the first, gaseous fuels such as methane are oxidized to yield CO which then reacts with water to form CO_2.

This CO₂ is collected and the remnant H₂ is used as fuel. The second method is mainly used in fossil fuel power plants and is therefore the most used method. Oxy-fuel combustion requires that fuel be burnt with pure oxygen as against air.

This yields cleaner combustion products since only CO₂ and water vapour are the products. Water is condensed and the CO₂ is collected.

In the next part, we will be discussing the transport and storage of sequestered carbon as well as the advancements man has made in the process.