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CDR – Overview

Carbon dioxide removal (CDR) encompasses all activities that remove CO2 from the atmosphere and safely store it away for decades to centuries. Sounds simple enough in theory but it is in fact a very complex topic. CDR is a term you will likely be hearing more often as the Intergovernmental Panel on Climate Change (IPCC) has recently stated that removals of CO2, and not just reductions, will be absolutely necessary to achieve our climate goals. As a result, we expect to see more and more players becoming involved in the market to satisfy the demand. Therefore, in a bid to level the playing field and make sure everyone has access to clear and concise information, we have created an overview of the most promising CDR methods available.

Overview Diagram

The Board

This figure gives a brief overview of established and emerging CDR methods. The figure has been adapted from the most recent contribution to the IPCC’s Sixth Assessment Report.

We adapted it to include the full range of CDR methods offered by Klimate and clear up some perceived terminology issues. We go more into depth on the individual components of the diagram below.

The Importance of Carbon Dioxide Removal

The IPCC defines CDR as “anthropogenic activities that remove CO2 from the atmosphere and store it durably in geological, terrestrial, or ocean reservoirs, or in products”. This act of removal is very important as emissions reductions are no longer good enough to achieve our climate goals: we now need to reverse GHG emissions. To read more about this please visit our ‘What is carbon removal’ page.

Board Explanation

Main Components

There is a lot going on in the diagram. So, we are going to walk through it part by part. CDR methods are categorized based on the removal process and the storage medium, and there are many ways that any one individual CDR method can be implemented. We delve deeper into these aspects below:

Removal Processes

We include five different removal (sequestration) processes: land-based biological, marine-based biological, hybrid, geochemical, and engineered. Photosynthesis is the CO2 removal process employed by land-based biological, marine-based biological, and hybrid methods. However, we believe there are enough differences between them to warrant distinctive categories. Land and marine-based biological are geographically differentiated, and hybrid solutions require a man-made middle step to achieve their desired effects. Geochemical removal processes broadly relates to the chemical reactions of natural earth materials (e.g., rocks) that can be utilised to draw down CO2 from the atmosphere. Finally, engineered solutions rely on technology for both sequestration and storage, but often the processes involved actually mimic or depend on natural processes.

Removal Processes

We include five different removal (sequestration) processes: land-based biological, marine-based biological, hybrid, geochemical, and engineered. Photosynthesis is the CO2 removal process employed by land-based biological, marine-based biological, and hybrid methods. However, we believe there are enough differences between them to warrant distinctive categories. Land and marine-based biological are geographically differentiated, and hybrid solutions require a man-made middle step to achieve their desired effects. Geochemical removal processes broadly relates to the chemical reactions of natural earth materials (e.g., rocks) that can be utilised to draw down CO2 from the atmosphere. Finally, engineered solutions rely on technology for both sequestration and storage, but often the processes involved actually mimic or depend on natural processes.

Timescale of Storage

The storage medium is inextricably linked with how long the carbon is ultimately stored, and this can be attributed to how well the carbon is isolated from the atmosphere. Geological formations, such as unminable coal seams, deep saline aquifers, mined salt domes, and active or depleted oil and gas reservoirs, offer the most durable, long-term storage options. After all, these formations have already proven that they are capable of storing carbon for millions of years. Minerals and marine sediments provide a middling degree of carbon storage. The ocean floor is so isolated from the Earth’s atmosphere and therefore, does not provide conditions conducive to rapid CO2 release. On the other hand, vegetation soils and sediments, and buildings are the most exposed to the atmosphere and so, provide the least amount of protection from CO2 rerelease.

Timescale of Storage

The storage medium is inextricably linked with how long the carbon is ultimately stored, and this can be attributed to how well the carbon is isolated from the atmosphere. Geological formations, such as unminable coal seams, deep saline aquifers, mined salt domes, and active or depleted oil and gas reservoirs, offer the most durable, long-term storage options. After all, these formations have already proven that they are capable of storing carbon for millions of years. Minerals and marine sediments provide a middling degree of carbon storage. The ocean floor is so isolated from the Earth’s atmosphere and therefore, does not provide conditions conducive to rapid CO2 release. On the other hand, vegetation soils and sediments, and buildings are the most exposed to the atmosphere and so, provide the least amount of protection from CO2 rerelease.

Implementation Options

Each CDR method has multiple ways in which it can be implemented. The decision as to which implementation option to choose is influenced by geography, resource availability, cultural and societal norms, and of course, financing. Some CDR methods simply have implementation options that are different flavours of the same thing, e.g., forestation approaches, whereas others have a much more distinctive array of implementation options. Some crossover exists between the implementation options of different methods, e.g., both biochar and timber can be used in construction. Implementation options that provide more than just a carbon capture and storage function or service are desirable as they address many of the other societal and environmental problems of the modern world.

Implementation Options

Each CDR method has multiple ways in which it can be implemented. The decision as to which implementation option to choose is influenced by geography, resource availability, cultural and societal norms, and of course, financing. Some CDR methods simply have implementation options that are different flavours of the same thing, e.g., forestation approaches, whereas others have a much more distinctive array of implementation options. Some crossover exists between the implementation options of different methods, e.g., both biochar and timber can be used in construction. Implementation options that provide more than just a carbon capture and storage function or service are desirable as they address many of the other societal and environmental problems of the modern world.

Conclusion

All of the CDR methods outlined above, and methods yet to be discovered and developed, will be required to work in harmony to tackle climate change. No single method will be our silver bullet. Knowledge dissemination also has an important role to play in in the fight, and so we hope that informational pages like this will help companies and organizations launch and bolster their Net Zero efforts. The Insights section of our webpage provides more information about the CDR methods and specific projects supported by Klimate.

Related topics

What is Carbon Removal?

Why combine methods?

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Finding the right way to remove your CO emissions can seem overwhelming. Luckily, we are always here to help. You can book a meeting to walk through how our solution might fit your needs, or simply send us a message.

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