Carbon removal involves extracting carbon dioxide (CO2) from the atmosphere. This process aims to decrease greenhouse gas concentrations and influence the Earth’s climate system. It’s a deliberate effort to mitigate CO2 buildup from human activities. The purpose of these efforts is to manage atmospheric carbon levels, contributing to broader climate objectives.
Why Removing Carbon is Crucial
Reducing new carbon emissions is a primary step in addressing climate change; however, active carbon removal is also necessary due to CO2’s long-term persistence in the atmosphere. Once released, a significant portion of CO2 can remain in the atmosphere for hundreds to thousands of years, continuing to contribute to warming trends. This extended atmospheric lifespan means that even with aggressive cuts to ongoing emissions, historical and residual CO2 will continue to affect the climate.
Achieving “net-zero” emissions, where remaining greenhouse gas emissions are balanced by removals, often requires active CO2 extraction. Climate models indicate that reaching ambitious temperature targets, such as limiting warming to 1.5 or 2 degrees Celsius, will likely require removing billions of tons of CO2 from the atmosphere annually. Therefore, carbon removal acts as a complementary strategy to emissions reductions, not a substitute. It addresses the legacy of past emissions and helps achieve deeper decarbonization targets that might be difficult to meet through emissions reductions alone.
Nature’s Role in Carbon Removal
Natural processes and ecosystems offer several pathways for removing carbon dioxide from the atmosphere. Afforestation and reforestation, which involve planting new trees and restoring degraded forests, are prominent examples. Trees absorb CO2 through photosynthesis, converting it into biomass like wood, leaves, and roots. A mature forest can store substantial carbon, acting as a carbon sink over its lifetime.
Soil carbon sequestration focuses on enhancing agricultural practices to increase carbon stored in soils. Techniques like no-till farming, which minimizes soil disturbance, and the use of cover crops, which keep soil covered, promote organic matter accumulation. This organic matter contains carbon, improving soil health while drawing CO2 from the atmosphere and holding it underground.
Ocean-based solutions also hold promise for carbon removal. Enhancing ocean alkalinity involves adding alkaline minerals to seawater, increasing the ocean’s capacity to absorb CO2. This mimics natural weathering reactions. Promoting large-scale seaweed cultivation also contributes. Seaweed absorbs CO2 during growth, and when harvested and potentially sunk to the deep ocean or used in long-lived products, it can prevent carbon from returning to the atmosphere.
Engineered Solutions for Carbon Removal
Technological approaches provide additional avenues for extracting carbon dioxide from the atmosphere or from concentrated emission sources.
Direct Air Capture (DAC)
Direct Air Capture (DAC) systems use chemical processes to filter CO2 directly from ambient air. These systems employ large fans to draw air over specialized sorbent materials that bind with CO2, which is then released and concentrated for storage or use. This method offers flexibility in location, as it does not need to be co-located with an emission source.
Bioenergy with Carbon Capture and Storage (BECCS)
Bioenergy with Carbon Capture and Storage (BECCS) combines energy generation from biomass with CO2 capture technology. Biomass, such as agricultural waste or dedicated energy crops, absorbs CO2 as it grows. When this biomass is used in power plants or industrial facilities, the resulting CO2 emissions are captured before they enter the atmosphere and stored underground. This process can achieve “net-negative” emissions if captured CO2 exceeds emissions from biomass cultivation and processing.
Enhanced Weathering
Enhanced weathering accelerates natural geological processes where minerals react with atmospheric CO2. For example, crushing silicate rocks like basalt into fine powders and spreading them on land increases their surface area, allowing quicker reaction with CO2 and water. This reaction converts CO2 into stable carbonate minerals or bicarbonate ions, which can then be transported to the ocean for geological storage.
Carbon Mineralization and Geological Storage
Carbon mineralization and geological storage provide methods for permanently storing captured CO2. Geological storage involves injecting compressed CO2 deep underground into porous rock formations, like depleted oil and gas reservoirs or saline aquifers, trapped by impermeable caprock. Carbon mineralization converts CO2 into stable, solid carbonate minerals, mimicking natural rock formation. This offers durable storage, preventing CO2 from re-entering the atmosphere.
The Path to Widespread Carbon Removal
Scaling up carbon removal efforts, whether natural or engineered, presents complex challenges and opportunities. Many of these technologies and natural solutions are in early stages of development; pilot projects show varying success. Long-term potential hinges on continued research, development, and larger-scale deployment. Demonstrating consistent and reliable operation is a significant hurdle.
Implementing carbon removal widely will require substantial financial investment. The costs associated with capturing, transporting, and storing CO2 can be considerable. Investment in infrastructure, research, and operations is necessary for commercial viability and widespread adoption. Attracting private and public capital will be important for advancing these technologies.
Government policies and regulatory frameworks play a role in driving the adoption and deployment of carbon removal technologies. Incentives like tax credits, carbon pricing, and direct subsidies can encourage investment and reduce financial risks. International cooperation is also important for sharing knowledge, developing standards, and facilitating cross-border projects. These policy levers can help create a market and regulatory environment conducive to scaling up carbon removal.