Is Carbon sequestration a key method for mitigating carbon emissions?

As a junior in the IB program at my high school, I recently started to brainstorm ideas for my 4,000 word extended essay. Looking into different questions regarding environmental sciences, I came across an interesting topic: carbon sequestration. At the same time, I had the privilege of visiting Prof. Rahimi’s lab in the University of Houston where his team develops a range of electrochemical processes to assist in mitigating climate change. https://teamrahimi.com/

So in this blog, I will be sharing my initial understanding of carbon sequestration.

Firstly, what is carbon sequestration? The idea is very similar to carbon capture which ‘captures’ carbon dioxide. Carbon sequestration, however, is the next step in the process in which the captured carbon dioxide is stored into various environmental sectors. There are many different forms of carbon sequestration including biological (carbon stored in vegetation like grasslands, soils, and oceans), geological (carbon injected into porous rocks), and technological (when carbon is stored and used as a resource). Technological sequestration is the most effective form of combating climate change because it allows carbon to be repurposed into helping create other materials. For example, stored carbon is used to produce graphene, a substance that is used in device screens. It is currently estimated that 90% of the emissions from fossil fuels can be captured for carbon capture and storage (CCS).

Currently, carbon sequestration does not have a significant impact on climate change. According to the Global CCS institute, in order to make a significant contribution against climate change, installed capacity of carbon dioxide must reach 5,600 million tonnes per annum. Unfortunately, in 2021, the overall carbon storage was only 40 million tonnes. 

The main issue with carbon sequestration is with the carbon sinks- where the carbon is stored. There are not enough carbon sinks to store every ton of carbon captured. To make matters worse, carbon sinks begin to degrade with each ton of carbon stored, making them more ineffective. 

Another concern with CCS is that carbon dioxide could leak out of their carbon sinks, contaminating nearby water sources, and polluting the surrounding air. Additionally, human-made tremors could cause pressure build-ups underground, something known as induced seismicity. 

A project called CarbFix2, held in Iceland, is working on testing how to store carbon as a mineral. Carbon dioxide is captured from a local power plant, is transported, and stored underground. However, they found a creative solution to the potential leakage of CO2. They decided to dissolve carbon dioxide in water before being stored, so that it is stored dissolved in a liquid rather than gas form. The carbon will form calcite when it is injected into basaltic rock. They are also tackling seismicity by closely managing the injection of dissolved carbon into rocks. The project found that 35% of carbon is captured from the plant, but could be scaled all the way up to 100% with the political incentive to invest in CCS. Projects like these prove to us that emerging processes like carbon sequestration can be crucial in fighting climate change. 

The economics behind the CCS process is a little murkier, however. It is very expensive for many corporations. A plant utilizing the CCS process uses more fuel than one without it. When CO2 is not produced in separately concentrated streams, the cost of CCS is far more expensive than when carbon is produced separately. Manufacturers should invest in researching how to produce CO2 in a separately concentrated stream in order to implement the CCS process to prevent emissions while also saving money.

Although carbon sequestration is a good idea to rid current emissions, it should not be the primary form of combating climate change. The best way to do so should be to prevent emissions from the beginning rather than trying to resolve the issue after being released into the atmosphere.