Technological Carbon Dioxide Removal🔗

Promote the use of carbon dioxide removal technologies like direct air carbon capture and storage (DACCS), ocean alkalinity enhancement (OAE), and enhanced mineralization. These methods rely on heavy industry to directly remove carbon dioxide from the atmosphere. While these technologies offer promising solutions for reducing atmospheric carbon, they require substantial energy and investment to implement on a large scale. Forms of CCS that are combined with energy generation are found under their respective sliders (coal, gas, and bioenergy).

Examples🔗

Advancements in various carbon dioxide removal (CDR) technologies through research and development, and government policies.
Support from businesses, land owners, and the general public to implement such technologies.

Carbon Dioxide Removal Methods🔗

The following methods of technological CO₂ removal can be explored in the En-ROADS simulator:

Direct air carbon capture and storage (DACCS) is an emerging technology that pulls CO₂ out of the air, where it is then stored in geological reserves. To get a net removal benefit, the captured carbon must be stored long term.
Ocean alkalinity enhancement (OAE) are technologies that increase the ability of the ocean to sequester carbon by increasing the natural buffering chemistry, either through spreading minerals on the ocean’s surface or using electricity to separate the seawater into acidic and alkaline components. This causes an increased flow of CO₂ from the atmosphere into the ocean and long-term carbon storage in the ocean without furthering acidification.
Enhanced mineralization entails mining specific rocks—like basalt—that can absorb CO₂ from the air and converting it to rock for long-term carbon storage.

Big Messages🔗

Technological Carbon Removal has the potential to pull significant amounts of carbon dioxide out of the atmosphere.
Even large amounts of CDR can be overshadowed by the massive volume of ongoing emissions if we do not reduce emissions by transforming our energy system.
Most of these technologies are still undergoing pilot testing, and do not exist at the level needed to deploy at a large scale.
To be successful, these technologies must store carbon (usually underground) for the indefinite future without leaking back into the atmosphere.

Key Dynamics🔗

Industry scale. View the graph “Bulk Material for Carbon Dioxide Removal” to see the scale of industrial production these approaches entail.
Carbon bathtub. CO₂ concentration in the atmosphere will continue to increase as long as CO₂ emissions exceed CO₂ removals, just as the level of water in a bathtub will continue to increase as long as the water entering the tub exceeds the water draining out. Learn more here.

Potential Co-Benefits of CDR Growth🔗

The scale up of many carbon removal approaches would result in vast new industries and businesses, which would create jobs.
OAE could help reduce ocean acidification in specific locations.
Enhanced mineralization can benefit soil by reducing its acidity.

Equity Considerations🔗

All of these methods would demand large amounts of energy. View the graph “Energy Used to Capture and Store Carbon” to see the energy usage they entail.
Many of the technological carbon removal approaches have not been developed at scale yet and pose unknown risks and consequences to the communities and ecosystems they are situated within.

Videos🔗

Afforestation & Technological CO₂ Removal

Slider Settings🔗

	status quo	low growth	medium growth	high growth
Percent of potential	0% to +10%	+10% to +40%	+40% to +70%	+70% to +100%

DACCS: The main Technological Carbon Dioxide Removal slider (or the “Direct air carbon capture and storage (DACCS) price” slider in the advanced view) controls the amount of revenue a DACCS facility could receive per ton of CO₂ captured. The amount of carbon dioxide removals (CDR) achieved depends on the economics and other assumptions. Default assumptions are set so that a maximum slider setting of $1000/ton CO₂ captured results in removals consistent with the Royal Society (2018) report (Table 2, Chapter 2). Different outcomes can be explored by adjusting the settings in the Assumptions view under the “Carbon capture and removals” section.

OAE: The main Technological Carbon Dioxide Removal slider (or the “Ocean alkalinity enhancement (OAE) price” slider in the advanced view) controls the amount of revenue an OAE facility could receive per nominal ton of CO₂ absorbed by seawater. The amount of CDR achieved depends on the economics and other assumptions. Default assumptions are set so that a maximum slider setting of $1000/ton CO₂ captured results in removals consistent with the National Academies (2022) report estimates for mineral-based and electrochemical potential. Different outcomes can be explored by adjusting the settings in the Assumptions view under the “Carbon capture and removals” section.

Model Structure🔗

The methods of CO₂ removal included are modeled independently. They each vary in their maximum sequestration potential, the year they might start to scale up, how long it takes them to be phased in, and the carbon leakage rate over time (stored carbon is not always permanent).

DACCS: En-ROADS represents both the economics and physics of DACCS. As an emerging technology, many parameters remain uncertain. The maximum deployment potential of DACCS is determined by the DACCS price and various parameters within the Assumptions view. These parameters include the time required to complete DACCS infrastructure, from planning through construction, the energy needed to operate DACCS (and how that might improve with technological advances), and the transport and storage of the captured CO₂. It also considers the supply curve—how much DACCS would be built if its cost were matched by revenue from markets or subsidies—as well as factors affecting cost, such as learning, siting limitations, and distance to storage sites. Users can adjust all these parameters in the Assumptions view.

Ocean alkalinity enhancement: En-ROADS represents both the economics and physics of OAE. As an emerging technology, many parameters remain uncertain. The maximum deployment potential of OAE is determined by the OAE price and various parameters within the Assumptions view. These parameters include the initial cost of OAE, the mix of electrochemical versus mineral-based methods, the energy and material needs of different pathways, the time it takes to complete new infrastructure, and the time it takes for OAE operations to affect the ocean’s chemistry. It also considers the supply curve—how much OAE would be built if its cost were matched by revenue from markets or subsidies—as well as factors affecting cost, such as learning, siting limitations, and coastal access. Users can adjust all these parameters in the Assumptions view.

Enhanced mineralization: En-ROADS represents the time it takes for the practice of enhanced mineralization to be adopted and the infrastructure to be built. After adoption, the gross amount of CO₂ removed by mineralization is a function of the land area the ground rock is applied to, the amount of rock per area, and the absorption potential of the type of rock. The net CO₂ captured is the gross amount of CO₂ removed minus the emissions from energy used to grind and spread the rock. Users can adjust all these parameters in the Assumptions view.