A carbon dioxide (CO2) pipeline is specialized infrastructure designed to transport large volumes of captured CO2 from industrial sources to a final destination. These pipelines are a fundamental component of Carbon Capture, Utilization, and Storage (CCUS) projects. They serve as the necessary link between facilities that capture carbon, such as power plants or cement factories, and the distant sites where the CO2 will be stored or repurposed.
Preparing and Transporting CO2
Moving CO2 through a pipeline requires an engineered process to ensure efficiency and integrity. The captured CO2 is first purified to remove impurities like water, hydrogen sulfide, and nitrogen oxides. This purification is important because CO2 mixed with water forms corrosive carbonic acid, which can quickly degrade the carbon steel used in pipeline construction.
After purification, the CO2 is compressed and cooled to achieve the supercritical phase. This is the optimal condition for pipeline transport, as it maximizes the amount of CO2 that can be moved by maintaining it above its critical temperature and pressure.
In this state, the CO2 exhibits properties of both a liquid and a gas, possessing a density similar to a liquid but a viscosity closer to a gas. This combination allows the CO2 to be pumped rather than compressed along the pipeline route, significantly reducing the energy required for long-distance transport. The pipelines are made from low-alloy carbon steel, similar to natural gas pipelines, but are designed to withstand the high pressures necessary to maintain the supercritical state.
End Uses for Captured Carbon Dioxide
Once the CO2 reaches its destination, it is primarily directed toward one of two major end uses: long-term geological storage or industrial utilization. Geological storage, also known as Carbon Capture and Storage (CCS), involves injecting the CO2 deep underground into specific rock formations for permanent sequestration. Suitable sites include deep saline aquifers, which are porous rock layers saturated with saltwater, or depleted oil and gas reservoirs, where the geology has already proven capable of trapping fluids for millennia.
The CO2 is injected at depths typically below 800 meters, where pressure and temperature conditions keep it dense. This long-term containment relies on overlying, impermeable caprock layers to prevent the buoyant CO2 from migrating back to the surface. Dedicated storage sites are designed for the sole purpose of climate mitigation, permanently removing the carbon from the atmosphere.
The other major destination for transported CO2 is Enhanced Oil Recovery (EOR), currently the most common commercial application in the United States. In EOR, the compressed CO2 is injected into mature oil fields to increase the amount of crude oil extracted. The CO2 acts as a solvent, reducing the oil’s viscosity and increasing the reservoir pressure to push the remaining oil toward production wells. While a significant portion of the injected CO2 remains trapped underground, EOR is classified as utilization.
Managing Safety and Environmental Risks
The expansion of CO2 pipeline networks requires rigorous safety protocols to manage potential hazards associated with transporting a high-pressure, dense-phase fluid. A significant public safety concern is the risk of a pipeline rupture, which could rapidly release a large volume of CO2 into the atmosphere. Because CO2 is colorless and odorless, and it is heavier than air, a leak can cause the gas to pool in low-lying areas, displacing oxygen and creating a serious asphyxiation hazard for humans and animals.
Engineers address this by using advanced pipeline materials and designs that minimize the risk of fracture propagation. The high-pressure nature of CO2 transport means that federal regulators are continually updating safety standards to ensure proper oversight of pipeline integrity and emergency response planning. The presence of impurities, particularly water, must be strictly limited, as the resulting carbonic acid can corrode the internal pipe walls, leading to eventual failure.
Concerns also extend to the long-term integrity of the geological storage sites themselves. Injecting large volumes of fluid deep underground increases the pore pressure within the reservoir rock, which can potentially reactivate pre-existing faults. This pressure change can trigger induced seismicity, or small, human-caused earthquakes. While most induced seismic events are microseismic and unfelt, a larger event could theoretically compromise the integrity of the caprock, creating a pathway for the stored CO2 to migrate.
To mitigate these risks, storage sites are subject to extensive monitoring and management programs, including seismic surveys and pressure sensors, to track the movement of the injected CO2 plume. Monitoring systems are deployed both deep underground to track pressure and plume migration, and at the surface to detect any potential leakage into the soil or atmosphere.
Current Status of CO2 Pipeline Networks
The United States currently operates the most extensive CO2 pipeline network in the world, with over 5,000 miles of operational pipelines. This network has been in use for decades, primarily serving the mature EOR industry in states like Texas, New Mexico, and Wyoming. Historically, much of the CO2 transported through these pipelines came from naturally occurring geological deposits rather than from captured industrial emissions.
The current infrastructure is highly localized and point-to-point, linking natural CO2 sources or industrial facilities to specific oil fields. However, to meet national decarbonization goals, a massive expansion is projected to be necessary, with estimates suggesting the network may need to grow to nearly 65,000 miles by 2050 to support widespread CCS deployment. This expansion represents a shift from a network built for EOR to one focused on permanent geological storage in new areas like the Midwest and Gulf Coast.
New pipeline projects are under development across North America, driven by economic incentives and the growing demand for carbon management solutions. The focus is increasingly on building large-diameter “trunk lines” that can connect multiple industrial emitters to centralized storage hubs, which is a major logistical and regulatory undertaking.