Carbon Capture and Carbon Removal: Differences and Examples
Carbon capture and carbon removal are two important strategies for addressing climate change. While their goals, methods, and applications differ significantly, both play crucial roles in mitigating global warming. This article explores the distinctions between these two approaches and provides examples to illustrate their practical applications.
Carbon Capture
Carbon capture focuses on collecting carbon dioxide (CO₂) emissions from industrial processes or energy production before they are released into the atmosphere. The captured CO₂ typically comes from large point sources, such as coal-fired power plants, steel mills, or cement factories. After capture, the CO₂ can be stored (CCS, Carbon Capture and Storage) or utilized (CCUS, Carbon Capture, Utilization, and Storage).
Main Methods:
1. Pre-Combustion Capture:
Before combustion, fuel is converted into synthesis gas, separating hydrogen from carbon dioxide. The CO₂ can then be captured and processed.
2. Post-Combustion Capture:
After fuel is burned, CO₂ is separated from the flue gas. Techniques such as chemical absorption and physical adsorption are commonly used.
3. Oxy-Fuel Combustion Capture:
Instead of air, pure oxygen is used for combustion, resulting in flue gas that mainly consists of CO₂ and water vapor. This simplifies the process of CO₂ separation and capture.
Example:
Norway’s Sleipner field is the world’s first commercial-scale carbon capture and storage project. Since 1996, it has captured and stored about 1 million tons of CO₂ per year by injecting it into a saline aquifer under the North Sea. This project effectively reduces greenhouse gas emissions.
Carbon Removal
Carbon removal involves directly extracting CO₂ from the atmosphere, achieving negative emissions and lowering atmospheric CO₂ concentrations. This approach is essential for offsetting residual emissions that are difficult to eliminate and for achieving net-zero targets.
Main Methods:
1. Nature-Based Approaches:
• Afforestation and Reforestation:
Planting new trees or restoring forests enables plants to absorb CO₂ during their growth, locking it in biomass.
• Soil Carbon Sequestration:
Sustainable agricultural practices—such as no-till farming and cover cropping—enhance soil organic carbon content.
2. Technological Approaches:
• Direct Air Capture (DAC):
CO₂ is removed directly from ambient air using chemical or physical processes. The captured CO₂ is then stored or utilized.
• Bioenergy with Carbon Capture and Storage (BECCS):
Biomass is used as an energy source, and the CO₂ generated during combustion or conversion is captured and stored, resulting in negative emissions.
Example:
Swiss company Climeworks has developed direct air capture technology that uses fans to draw in air, chemical sorbents to capture CO₂, and heat to release concentrated CO₂ for storage or use. The company has pilot projects in multiple countries, showcasing the potential of removing CO₂ directly from the atmosphere.
Differences Between Carbon Capture and Carbon Removal
1. Objectives:
• Carbon Capture: Focuses on preventing new emissions from entering the atmosphere.
• Carbon Removal: Aims to reduce the concentration of existing CO₂ in the atmosphere.
2. Technical Pathways:
• Carbon Capture: Typically involves modifying or adding equipment to existing industrial processes.
• Carbon Removal: Encompasses both nature-based solutions and purpose-built technological systems, offering a broader range of approaches.
3. Application Scenarios:
• Carbon Capture: Applied at large, stationary emission sources such as power plants and factories.
• Carbon Removal: Has global applicability, particularly in sectors with hard-to-abate emissions, or for offsetting unavoidable emissions.
Conclusion
Carbon capture and carbon removal play complementary roles in tackling climate change. While the former seeks to reduce new emissions, the latter focuses on lowering the concentration of CO₂ already present in the atmosphere. By leveraging both strategies, we can make meaningful progress toward global greenhouse gas reduction targets and drive sustainable development.