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Frequently Asked Questions

General CCUS

What is carbon dioxide? Does carbon dioxide explode?

Carbon dioxide (CO₂) is a non-flammable, non-explosive, naturally occurring gas. Humans exhale it with every breath; it is used in hundreds of products including soda, dry ice and fire extinguishers; and is a necessary component of plant growth. It’s the bubbles in your soda or beer.

How is carbon dioxide transported and stored?

For the purposes of a carbon capture and storage (CCS) project, CO₂, once captured, is compressed to turn it from a gas into a state called a supercritical (or dense) fluid. This allows the CO₂ to be handled like a fluid for more e􀆯icient transport, typically via pipeline, and it occupies less space in the subsurface when injected for storage.

What happens if carbon dioxide leaks?

In the unlikely occurrence that CO₂ escapes from a pipeline or through a wellbore to the surface, most of the CO₂ quickly evaporates into the air (reverting to its original gaseous state), although it is common to see dry ice (solid CO₂) around the site as well. The gas typically requires little to no clean-up.

In the event of a leak, pipeline and injection well systems are designed to automatically shut down, ceasing all operations until the cause is determined and repaired. Operation does not resume until any issues are fixed and the regulator has approved CO₂ injection can restart.

Why do we call it carbon capture, CCS, or CCUS?

Carbon capture is the act of separating CO₂ molecules from the exhaust or flue gas of an industrial facility such as a power plant or ethanol plant; this is known as point source capture (PSC). Carbon capture technology has been used for decades, particularly on natural gas processing systems at oil and gas fields.

Carbon capture can also remove CO₂ directly from the atmosphere, which is known as Direct Air Capture (DAC). DAC is a more recent development and is not a widely deployed approach currently.

In Carbon Capture and Storage (CCS), captured CO₂ is injected deep underground (nearly 2/3rds of a mile or more) into porous and permeable rock layer(s), covered by an impermeable cap rock that keeps the CO₂ contained within the storage rock layers.

In carbon capture, use, and storage (CCUS), the captured CO₂ is used for beneficial purposes. The most common use for CO₂ in terms of volume is for enhanced oil recovery (EOR) where CO₂ is injected into a mature oil reservoir to mobilize and produce more oil that has been left behind after initial production. Nearly all that CO₂ (>95%) ultimately ends up being trapped in the subsurface at the conclusion of the EOR activity. Other uses for CO₂ include medical purposes, carbonating beverages, and enhancing crop growth in a greenhouse.

Are there successful CCS/CCUS projects in Alaska or elsewhere?

Yes, in Alaska CCUS has, via enhanced oil recovery (EOR), been occurring in oil fields on the North Slope since the 1980s. These efforts have increased oil recovery by over 500 million barrels of oil. Elsewhere in North America, about 2.5 million tonnes per year is being captured in North Dakota and shipped to Canada for EOR and/or storage since 2000. North Dakota also has 3 other projects that are injecting and storing CO₂, including at two ethanol facilities and at Dakota Gasification Company’s synfuels plant, with each beginning operation in the last 2-4 years. In Saskatchewan, the Boundary Dam power plant has captured CO₂, for injection since 2014, while in Alberta, the Alberta Carbon Trunk Line has been transporting captured CO₂, for EOR since 2020.

The Global CCS Institute’s 2025 Global Status of CCS reports that there are 77 active, commercial-scale CCS projects globally.

Why do companies/organizations pursue CCS projects? Why is it being considered in Alaska?

CCS may be pursued for an array of reasons, and each company or organization has their own reasons or goals. Some examples include: 1) a company may need to comply with regulations or meet CO₂ emissions targets set by a government agency. 2) Energy companies may have financial incentives, such as low carbon fuel markets where CCS can lower their carbon intensity, thus leading to a higher valued product. 3) Company commitments, investors, or customer expectations may also drive a company to produce low-carbon products or low-carbon energy.

Regardless of the reason, many companies see the value in pursuing CCS for their industry, whether it is in power generation, oil and gas production, or other industrial processes.

Specific to southcentral Alaska, a shortage of natural gas is forcing the energy industry to consider other options to provide power to the region. Due to the state’s abundant coal supplies, the most affordable, reliable, and secure option for power generation is with a coal-fired power plant that is built with CCS technology.

In addition to the power/electricity industry, the oil & gas industry in Alaska needs to stay competitive in U.S. west coast markets. These markets are pushing oil producers to provide lower carbon intensity oil. To avoid Alaska companies from being forced out of the market, CO₂-based enhanced oil recovery (EOR), or CCUS, is the most viable option to keep Alaskan oil competitive in these marketplaces.

 

What is the current federal policy on CCUS?

Updates made in the One Big Beautiful Bill passed on July 4, 2025, increased the 45Q credit paid to $85 per ton CO₂ for enhanced oil recovery (same as for geologic sequestration) and indexes the 45Q tax credit dollar amount with inflation.

Current federal regulations require a new coal fired power plant in Alaska to capture 40% of the CO₂ and to capture 70% to be eligible for the 45Q credit.

What CCUS-related projects are underway in Alaska?

Regulatory

The Alaska Oil and Gas Conservation Commission (AOGCC) is seeking Class VI injection well primacy from the Environmental Protection Agency (EPA) (SB48, May 2023). Class VI wells are designed specifically for injection and storage of carbon dioxide. Gaining primacy over this class of wells would allow AOGCC to directly regulate and oversee the permitting, development, and stewardship of these wells in Alaska, as it currently does with other oil and gas wells in Alaska. For more information, visit the AOGCC website.

The Alaska Department of Natural Resources (DNR) carbon storage regulations (HB50, July 2024) took effect February 2025. For more information, visit the DNR Division of Oil and Gas website.

Federal DOE Funded Awards

DNR has a $1M carbon storage public information sharing geologic database project underway. Public outreach partners include the University of Alaska Fairbanks Alaska Center for Energy and Power and Alaska Resource Education.

The University of Alaska Fairbanks Institute of Northern Engineering is leading an $11M Alaska Railbelt Carbon Capture and Sequestration (ARCCS) CarbonSAFE Phase II storage assessment with the Energy and Environmental Research Center and Advanced Resources International. ARCCS is evaluating CCS for a new -fired power plant and two existing natural gas power plants in Anchorage operated by Chugach Electric Association. For more information, visit the ARCCS project page.

Arctic Slope Regional Corporation Energy Services (AES), Santos, and Repsol are carrying out a $3M Direct Air Capture Pre-Feasibility Study ongoing with the U.S. Department of Energy.

AES and Santos were selected for award on a $62M CarbonSAFE Phase III project focusing on subsurface site characterization and permitting for a potential North Slope project site called North to the Future CCS Hub.

Additional Studies

The U.S. Department of Energy and the Japan Ministry of Economy, Trade and Industry announced a cross-border CCS import to Alaska feasibility study, with Phase I focused on transportation feasibility. Hilcorp, Sumitomo, and K Line signed joint study agreement for CCS feasibility of imports from Japan to Alaska for sequestration.

What industries use carbon capture?

Carbon dioxide capture is being applied in manufacturing plants for cement, iron, steel, chemicals, and ethanol, in natural gas processing, oil refining, and power and heat generation.

Does CO2 injection and storage work?

Yes, underground CO₂ injection first began more than 50 years ago in western Texas. Most CO₂ injection has occurred as part of EOR operations. While the goal is different than a project that is only looking to store CO₂, scientists and engineers have learned a great deal about CO₂'s behavior in the subsurface via different monitoring strategies and how to manage project infrastructure like pipelines and wellbores to be compatible with exposure to CO₂.

In Alaska, since 1986, carbon capture technology has been used to process the entire produced gas stream in Prudhoe Bay. The Central Gas Facility separates carbon dioxide from the natural gas stream (12.5% CO₂) and manufactures miscible injection gas (20% CO₂) for enhanced oil recovery. The Prudhoe Miscible Gas Injection Project has increased field recovery by over 500 million barrels of oil.

Now, CCS projects that are injecting CO₂ for storage purposes can benefit from the knowledge gained and technologies developed during EOR operations.

Is CCS/CCUS economically feasible? What is motivating companies to pursue CCS/CCUS?

Yes, it is feasible.

CO₂ capture costs have been coming down in recent years as advances have been made in capture technology. For example, CO₂ captured from a coal-fired power plant had been estimated in the $50-$60/tonne, but recent estimates suggest capture costs have dropped to ~$35/tonne. These savings are significant given large-scale projects are potentially injecting millions to tens of millions of tonnes of CO₂ annually.

While capture costs have dropped, there are economic incentives that are driving the CCS/CCUS markets forward. U.S. IRS Section 45Q tax credits provide $85/tonne of CO₂ stored for both CCS and enhanced oil recovery (EOR). Energy producers can benefit from low carbon fuel markets where lower carbon intensity products will sell into restrictive markets, and CCS is a key mechanism for companies to meet those restrictions. EOR benefits from the sale of produced oil on top of the 45Q tax credits.

Furthermore, market forces may motivate companies to invest in CCS. For example, Alaskan oil may be forced out of west coast markets as state’s require lower carbonintensity oils. Investors or customer bases may also demand and prefer low carbon products that can also drive companies to invest in CCS for their facilities.

Carbon dioxide transportation

Is transportation of carbon dioxide in pipelines safe?

Pipeline transportation is safe, and it is far safer than other modes of transport, including trucking and rail.

Underground carbon dioxide (CO₂) injection first began more than 50 years ago in western Texas. Decades of data have helped us understand how CO₂ behaves and how to safely transport it through pipelines. Today, millions of metric tons of CO₂ are safely transported daily across the country through 5,000+ miles of pipelines. Before a CO₂ storage project ever begins, acceptable routes are identified and evaluated for the new pipelines.

Pipelines and storage sites have stringent regulations, monitoring, and mitigation requirements. Alaska prioritizes significant planning and research, training, and technology into all aspects of pipeline safety to be prepared for any unexpected scenarios.

How are underground CO2 pipelines monitored?

Multiple safeguards and protections are put in place for storage sites and pipelines. Safety is ensured through rigorous site selection, extensive monitoring, and regulatory oversight. Alaska requires extensive review and approval of plans to operate pipelines and storage facilities and inject carbon dioxide (CO₂). In addition, the U.S. Environmental Protection Agency requires a monitoring, reporting, and verification plan for sequestered CO₂. Typical project requirements include:

• Class VI well construction with surface casing/ cementing protecting water resources; cementing from the surface to the injection point; and corrosionresistant materials.
• Next-Level Monitoring: multi-layer, multi-protection, multi-action 24/7/365
• Operational monitoring for temperature and pressure changes that could indicate early anomalies.
• Leak detection and alerts.
• Deep underground monitoring to ensure that the CO₂remains securely in the storage zone.
• Surface and near surface monitoring to ensure no environmental effects.
• Surface water, groundwater and soil regular testing
• Automatic shutoff requirements
• Risk assessment and mitigation including comprehensive manuals at each site and control center with actions for various scenarios.
• Post injection site care and closure, including continuous monitoring after injection ends, until it is demonstrated that the CO₂ stops moving (at least 10 years)
• Pipeline operators partner with local emergency managers to develop and review emergency response plans and conduct regular training and drills.
• Comprehensive financial burden on storage companies to cover the cost of any necessary corrective action, injection well plugging, site care or closure, and emergency or remedial response. 

Source: North Dakota Industrial Commission Understanding CO2 Storage and Pipeline Safety

What happens if a leak is detected?

Pipeline systems developed for CCS projects today are designed with sensitive leak detection systems, alerts, and shutoff equipment. The systems detect changes, such as drops in pressure, which may be indicative of an issue such as a leak. Valves along the length of the pipeline (typically averaging every 10 miles?) are designed to shut down if a leak is detected, limiting the carbon dioxide (CO₂) volume released. The first step to any leak event is a shutdown of the CCS system to mitigate the loss of CO₂. From there, an investigation of the leak event and necessary repairs and remediation are performed. Before operations can resume, the regulatory authority needs to agree and approve that the operation is safe to resume.

Carbon dioxide geologic storage

What is the difference between storage and sequestration?

Storage and sequestration are used interchangeably in terms of CCS.

Storage is mostly used for the ARCCS project.

What is “cap rock”?

Cap rock is low-permeability rock layer that does not allow gas and liquids to move upwards through it. Cap rock is the layer that ensures injected CO₂ remains in the storage layer and doesn’t impact groundwater supplies or the surface environment.

Cap rocks have successfully held oil and natural gas (and other fluids) for millions of years, therefore demonstrating their ability to also contain CO₂.

How deep does CO2 need to be injected?

Carbon dioxide (CO₂) is stored underground at depths where the pressure is high enough, so it is a liquid rather than a gas, typically 3000 ft or deeper.

Liquid CO₂ takes up a much smaller space—a hundred times smaller than as a gas.

What happens after carbon dioxide is injected underground?

When carbon dioxide (CO₂) is injected underground, it flows through the reservoir and interacts with the water and rocks it contacts. Some CO₂ dissolves into the water—like a soda—and is trapped in immobile reservoir water, some is trapped by capillary forces, and the remaining CO₂ is trapped by the cap rock. Depending on the reservoir rock minerals, CO₂ can also chemically convert into a carbonate rock.

How is injection controlled to avoid fracturing the cap rock?

Before CO₂ is ever injected, the project operator is required to perform testing of the cap rock to understand how much pressure the layer can be exposed to without fracturing (commonly referred to as a layer’s fracture pressure). This information is provided to the regulator and ensures safe operations. The injection well is constructed with downhole pressure sensors to continuously monitor the pressures throughout a project’s lifetime. This ensures pressures are below the permitted fracture pressure, with a safety margin, to ensure the integrity of the cap rock is maintained.

How is CO2 plume movement predicted and tracked?

Geological and engineering models are used to predict the vertical and areal movement of carbon dioxide (CO₂) through the reservoir.

The example shown below is a model predicting the pressure and CO₂ saturations during injection into the reservoir. Note the highest pressures occur at the point of injection, i.e. where the well meets the rock, and reduces as the injected CO₂ moves through the reservoir and the pressure dissipates.

Source: Intera modeling for U.S. Department of Energy

CO₂ can be tracked in the subsurface by different methods. The most common technique is through what is called a geophysical, or seismic, survey. This method uses an array of sensors, installed at the surface, along with a vibration source (typically dynamite or vibrator trucks). The sensors record the vibrations and their reflection in the subsurface rock layers to create an image of the subsurface. The method is similar to an X-ray or an MRI for the human body. In the geophysical survey, scientists can see different rock properties and the presence of fluids within those rock layers. Because CO₂ has different properties than native fluids, scientists can see the presence of CO₂ in these images, thus creating a picture of where the CO₂is underground. The geophysical surveys are often the preferred method required by regulators to understand the movement of CO₂ in the subsurface.

By comparing the geologic model predictions and the geophysical survey, the project operator can understand where the CO₂ is and where it is expected to be in the future, allowing them to manage the operations to ensure CO₂ is staying in the permitted subsurface areas.

 

 

What happens if an earthquake fractures the well casing seal?

The site is screened for geologic integrity and stability. There are oil and gas reservoirs nearby that have been there for millions of years and have survived all kinds of earthquakes. We find geologically stable sites like those reservoirs and design wells to be strong enough to survive earthquakes, just like we design buildings to survive earthquakes.

There are hundreds of wells in the Cook Inlet and Kenai Peninsula and thousands on the North Slope. All experience earthquakes, and many wells are decades old. The Alaska oil and gas industry and the Alaska Oil and Gas Conservation Commission (AOGCC) have decades of experience designing wells with the threat of earthquakes in mind. Wells are designed with multiple barriers to prevent the migration of fluids and with materials proven to be effective in Alaska’s challenging environments.

What happens if a leak is detected?

The first step to any leak event is a shutdown of the CCS system to mitigate the loss of CO₂. From there, an investigation of the leak event and necessary repairs and remediation are performed. Before operations can resume, the regulatory authority needs to agree and approve that the operation is safe to resume.