Capture vs. Remove: Comparing CCS and CDR Methods & Technologies

Introduction
What Are CCS and CDR?
CCS: Preventing Emissions from Industry
CDR: Removing CO2 from the Atmosphere
Complementary Roles of CCS and CDR
Carbon Hubs and Clusters: Collaborating to Store CO2
Policy, Public Perception, and Economic Incentives
Conclusion

Introduction

Atmospheric CO₂ levels are currently at their highest in millions of years, largely due to centuries of industrialization and significant land-use changes. These human activities have disrupted the Earth's natural carbon balance, leading to increased greenhouse gas concentrations and global temperature rises. Scientists warn that this warming could lead to profound climate changes, including rising sea levels as polar ice melts.

Avoiding the most extreme effects of global warming means reducing emissions from industry and transport, as well as ceasing unsustainable land and forest management, which releases billions of tonnes of CO₂ annually.
Decarbonizing means not only transitioning from the burning fossil fuels to the use of clean energy but also preventing the release of CO₂ from industries which do not have obvious pathways to cutting back emissions. In addition, it will require advancing and deploying technologies that actively remove CO₂ from the atmosphere, using a combination of engineered approaches and nature-based solutions.

Carbon Capture and Storage (CCS) technologies aim to target the emissions from industries which are otherwise hard to decarbonize, capturing CO₂ before it reaches the air and then securely storing it deep underground.

Meanwhile, CO₂ Removal (CDR)encompasses natural and engineered methods to extract CO₂ from the atmosphere and store it in sinks like trees, soils, oceans, or carbonate minerals, where it can remain for decades to millions of years.

Both CCS and CDR have the potential to play key roles in limiting global warming, but their advocates face the same challenge: proving they can be scaled enough to significantly impact future CO₂ levels. Additionally, understanding the broader picture—how each approach can complement the other and integrate with broader decarbonization efforts—will be fundamental to their success.

What Are CCS and CDR?

While Carbon Capture and Storage (CCS) and Carbon Dioxide Removal (CDR) share the goal of making a significant impact on future CO₂ levels, they target different stages of the emission cycle and use varied approaches. CCS captures CO₂ before it is emitted from industrial sources, such as power plants and cement factories, whereas CDR focuses on removing CO₂ already present in the atmosphere.

Carbon Capture and Storage (CCS) is an engineered technology designed to capture CO₂ emissions at their source. It is particularly useful for hard-to-abate sectors like steel, cement, and chemical manufacturing, where emissions are inherent to industrial processes and difficult to eliminate. The captured CO₂ is then transported to a geological formation where it is stored permanently, preventing it from entering the atmosphere. CCS focuses on preventing ongoing emissions and is particularly important for industries that cannot easily transition to low-carbon alternatives.
On the other hand, Carbon Dioxide Removal (CDR) targets legacy emissions—the CO₂ already present in the atmosphere due to centuries of industrial activity. CDR includes a range of technologies and natural processes aimed at reducing atmospheric CO₂ concentrations. These approaches can be broadly divided into engineered solutions, like Direct Air Capture (DAC), and nature-based solutions, such as reforestation and soil carbon sequestration.

CCS: Preventing Emissions from Industry

How CCS Works
CCS involves three main steps:

Capture: CO₂ is captured from industrial sources like power plants using one of several technologies—pre-combustion (removing CO₂ before fuel is burned), post-combustion (capturing CO₂ after combustion), and oxy-fuel combustion (burning fuel in pure oxygen to make CO₂ capture easier).
Transport: Once captured, the CO₂ is compressed into a liquid and transported to a storage site via pipelines, trucks, or ships.
Storage: The CO₂ is injected deep underground into geological formations, such as depleted oil fields or saline aquifers, where it is stored permanently.

Potential and Applications of CCS
CCS plays a crucial role in hard-to-abate sectors, where reducing emissions is especially challenging. For example, cement production and steel manufacturing inherently produce CO₂ as part of their chemical processes. Without CCS, these industries will struggle to decarbonize.
The continued use of fossil fuels, especially coal, to generate electricity remains highly contentious given the availability of cleaner alternatives like wind and solar. However, economic and political realities in certain countries suggest that coal-fired power plants will likely remain operational for the foreseeable future. The critical question is whether CCS can offer a viable solution to reduce the environmental impact of coal combustion, or if the significant costs of installing and operating carbon capture technology—along with the logistical challenges of storing captured CO₂—will render these plants economically unfeasible, particularly as the costs of renewable energy generation.
Sitting at the intersection of CCS and CDR is Bioenergy with Carbon Capture and Storage (BECCS), in which crops or other biomass is combusted to generate energy, while capturing and storing the resulting CO₂ emissions. Since biomass absorbs CO₂ as it grows, and its combustion emissions are captured, BECCS offers the unique potential to generate electricity with negative emissions. However, when evaluating the overall carbon balance, it is important to account for lifecycle emissions, the CO₂ released from all BECCS activities such as the cultivation, transportation, and processing of biomass.

Challenges for CCS

High Costs: The capture phase, which involves separating CO₂ from other gases, can account for up to 80% of the total cost. Without significant financial incentives or carbon pricing mechanisms, the economic viability of CCS remains a major challenge.
Energy Consumption: CCS is energy-intensive, particularly during the capture and compression phases, which can limit its overall efficiency.
Infrastructure Needs: Building the infrastructure to transport and store CO₂, including pipelines and storage hubs, is costly and requires extensive coordination across industries and governments.
Public Acceptance: There are concerns about the long-term safety of CO₂ storage, particularly regarding potential leaks from underground storage sites. Public perception plays a crucial role in the success of CCS projects.

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CDR: Removing CO₂ from the Atmosphere

How CDR Works
CDR methods focus on removing CO₂ from the atmosphere and can be grouped into nature-based and engineered approaches:

Nature-Based Solutions:

Reforestation and Afforestation: Planting trees to absorb CO₂ through photosynthesis. Forests act as carbon sinks, storing carbon in biomass and soils.
Soil Carbon Sequestration: Improving agricultural practices to increase the carbon content stored in soils.
Ocean-Based Approaches: Techniques like iron fertilization to enhance oceanic CO₂ uptake through phytoplankton growth.
Enhanced Rock Weathering: This method accelerates the natural weathering of silicate rocks, which absorb CO₂ and transform it into stable minerals over long timescales.

Engineered Solutions:

Direct Air Capture (DAC): Machines use chemical processes to extract CO₂ directly from the air and store it underground. While DAC provides precise control over CO₂ removal, it remains extremely expensive. Since CO₂ makes up only about 0.04% of the air, capturing it efficiently requires a lot of energy.
This low concentration means that DAC systems must process vast volumes of air to capture significant amounts of CO₂, making the process energy-intensive and costly in terms of both infrastructure and operation.

Potential and Applications of CDR
CDR technologies offer the potential to achieve negative emissions, a crucial element for offsetting legacy CO₂ emissions. Unlike CCS, which focuses on preventing ongoing emissions, CDR aims to reverse the damage caused by historical emissions. As the world works toward net-zero goals, CDR will become increasingly important for addressing the CO₂ already present in the atmosphere.
Challenges for CDR

Energy and Resource Requirements: Technologies like DAC require large amounts of energy to operate, and scaling them up will require significant investment in renewable energy sources to avoid offsetting their carbon benefits.
Land Use: Nature-based solutions like reforestation demand vast amounts of land, which can lead to conflicts with agricultural or urban development.
Technological Readiness: While natural solutions like reforestation are well understood, many engineered CDR methods are still in the early stages of development and need further refinement to become cost-effective at scale.
Monitoring and Verification: Ensuring that CO₂ is permanently stored and accurately quantifying the amounts removed are critical for the credibility of CDR methods, particularly for carbon markets.

Complementary Roles of CCS and CDR

While CCS and CDR have distinct goals and methods, they are complementary technologies that together can form a crucial part of climate mitigation strategies:

CCS for Ongoing Emissions: CCS is essential for industries that cannot easily transition to low-carbon processes, offering a solution to capture emissions before they enter the atmosphere.
CDR for Legacy Emissions: CDR addresses the CO₂ already in the atmosphere, making it crucial for achieving net negative emissions and restoring atmospheric balance.

In practice, a combination of CCS and CDR will likely be needed to meet global climate targets. The Intergovernmental Panel on Climate Change (IPCC) and International Energy Agency (IEA) have indicated that nearly all feasible pathways to net-zero emissions include both technologies.

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Carbon Hubs and Clusters: Collaborating to Store CO₂

Capturing huge volumes of CO₂ will be pointless unless there is a way to dispose of it. Developing the necessary underground storage sites as well as the infrastructure of pipelines, railways and possibly shipping terminals required to move the CO₂ to these locations from the point of capture will be hugely expensive. The solutions for overcoming this is the development of carbon hubs and clusters. These hubs collect CO₂ from multiple industrial sources within a region and transport it to a shared storage site. By clustering facilities together, economies of scale can be achieved, reducing costs and making CCS more financially viable.

Policy, Public Perception, and Economic Incentives

Both CCS and CDR will require robust policy support and economic incentives to scale up. Carbon pricing, for example, assigns a value to captured or removed CO₂, encouraging investment in these technologies. Governments can also provide tax incentives, subsidies, or direct funding for research and development to accelerate the deployment of both CCS and CDR.
Public perception will be critical to the success of these technologies so that clear communication about their benefits, safety, and necessity will be key to gaining support.

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Conclusion

As discussed, if Carbon Capture and Storage (CCS) and Carbon Dioxide Removal (CDR) are to become essential technologies in the fight against climate change, scaling them up to gigatonne levels will require significant technological innovation, policy support, public acceptance, and substantial infrastructure investment, alongside the cooperation of a wide array of industries.
Currently, neither technology can substitute for the urgent need to reduce emissions through renewable energy adoption and energy efficiency. Whether CCS and CDR become indispensable tools in achieving the deep decarbonization necessary to avoid catastrophic climate impacts will depend on the actions taken by industry and governments in the coming years.

The CDR & CCS Landscape...

Related Pages:

Overview

Capture vs. Remove

Research

Web Resources