Best practices for carbon dioxide transportation and storage

Managing industrial emissions through CCUS is becoming increasingly common to prevent harmful CO₂ greenhouse gas (GHG) release into the atmosphere. These methods are particularly attractive because they enable carbon dioxide emission-heavy processes to meet regulatory targets. They are especially valuable when opportunities for reducing GHG output via process efficiency improvements or renewable power sources are limited.

While significant focus is placed on developing efficient carbon capture methods, there is plenty of activity downstream in the value chain as well. After carbon dioxide gas is captured, it needs to be compressed, sometimes into a liquid state. Then, it is safely transported to a carefully selected location for its use or storage. Numerous factors must be considered, including distance, geography, existing infrastructure, environmental impact and cost of transport.

Currently, three primary modes of transportation dominate the landscape: pipelines, overland vehicles and seafaring vessels. Each of these methods is better suited to certain applications and less fit for others. Regardless of the approach, establishing functional logistics requires innovative solutions and robust infrastructure to ensure the long-term success of CCUS as an emissions mitigation strategy.

Pipelines are the most established and often the most economically viable option for transporting large volumes of CO₂ over long distances, especially over land. In some cases, existing natural gas pipelines can be repurposed for carbon dioxide transport, providing a cost-effective solution that utilizes existing infrastructure. This approach also minimizes the environmental impact of constructing new facilities.

However, repurposing pipelines for carbon dioxide transport requires careful assessment. Potential modifications are needed to ensure compatibility with the different properties of this compound, primarily its corrosive nature and higher-pressure requirements. While natural gas pipelines are often limited to 90 bar (1,300 psi), carbon dioxide sometimes requires ratings up to 150 bar (2,175 psi) for long distance transport.

Trucks and rail provide a flexible option for transporting smaller volumes of CO₂, particularly over shorter distances and in areas where pipeline infrastructure is limited. Their versatility makes them suitable for transporting carbon dioxide between capture sites and local storage facilities. They can also gather smaller volumes from various sources and deliver them to central hubs for larger shipments. However, reliance on land vehicles for CO₂ transport becomes costly over long distances, especially trucks, which also contributes to traffic congestion and diesel fuel emissions.

Ensuring the safe and efficient transport of carbon dioxide requires adherence to regulations and purity standards. While specific codes vary by region, carbon dioxide is classified as a hazardous material at high concentrations. Its transport is subject to rules similar to those governing natural gas in each locality. These regulations for safe handling address pipeline integrity, leak prevention and emergency response protocols.

Additionally, CO₂ purity is critical, both for end-use applications and transportation safety. Impurities like water, hydrogen sulfide and nitrogen oxides can cause chemical reactions, corrosion and product defects.

Once delivered, carbon dioxide must be either used in an industrial process or safely stored to prevent its release into the atmosphere. The most frequently selected storage locations are cavernous geological formations, although deep-ocean sequestration is attracting growing interest.

When storing carbon dioxide in geological formations, it is injected deep underground, often more than a kilometer below groundwater level, into carefully selected and monitored sites. Chosen locations are typically preexisting underground reservoirs, including depleted oil and gas fields, deep saline aquifers and coal seams that cannot be mined. These porous rock formations are typically capped with a non-porous "cap rock" to prevent CO₂ leakage.

Underground storage has provided a safe method for sequestering carbon dioxide for thousands of years. The U.S. Geological Survey (USGS) estimates that the United States has the geologic formations to store approximately 3,000 metric gigatons of carbon dioxide. However, selecting suitable storage sites requires extensive geological surveys and modeling to ensure the formation’s integrity. This process also aims to minimize potential risks, such as induced seismicity and impacts on groundwater resources.

While geological storage remains the most viable option for the foreseeable future, researchers continue to explore alternative methods. Mineral carbonation, for example, mimics natural geological processes by reacting carbon dioxide with elements in the earth to form stable carbonate minerals, effectively locking away carbon for long periods of time. Although long-term storage is promising, this method demands substantial energy and faces obstacles in terms of cost, scalability and resource access.

Alternatively, carbon dioxide can be injected into rock formations beneath the seabed. The North Sea in Europe, for instance, has the potential to store approximately 100 billion tons of carbon dioxide within its vast sandstone layers. This equates to almost three years’ worth of all carbon dioxide emitted globally.

Accurate measurement and monitoring with the right instrumentation are essential throughout the entire CCUS chain to ensure process efficiency, safety and environmental integrity. During transportation, carbon dioxide pressure, temperature, flow and quality must be measured in pipelines and at terminals to secure safe transport as well as accurate custody transfer.

Regardless of the chosen storage method, comprehensive monitoring is critical to ensure long-term site integrity and prevent CO₂ leakage back into the atmosphere. Effective tracking of carbon dioxide in storage reservoirs demands advanced technologies and sophisticated gas detection systems to stay informed about its movement and behavior. Continuous and robust measurement helps detect potential anomalies and leaks early on, providing prompt notification so personnel can intervene and minimize environmental risks.

Once captured, decisions must be made about carbon dioxide’s destination and the means to get it there. Ongoing research and significant investment from both public and private stakeholders are essential for scaling up transport and storage infrastructure necessary to reduce GHG emissions. This will improve the technological capabilities and economic viability of CCUS equipment, facilitating its widespread adoption in industry.

Capturing CO₂ from industrial product process streams is a crucial first step in the CCUS value chain. However, its long-term success relies on developing safe, efficient and sustainable transportation, utilization and permanent storage solutions. Top transportation contenders are pipeline, overland vehicle and sea-faring methods, while geological formations are best prepared for storage.

Streamlining efficiency and developing other options requires alignment among governments, process manufacturers, researchers and communities to address the technical, economic, regulatory and social challenges. However, investment in these capabilities is expected to increase the positive impact of CCUS on GHG reductions over the coming decades, helping industry achieve ambitious net-zero targets to create a more sustainable future.