Carbon capture works: By catching carbon as it leaves smokestacks, it’s possible to remove emissions from the atmosphere, mitigating climate change while empowering energy independence.

Carbon capture is also safe: Technology to inject carbon dioxide (CO2) into underground storage uses highly regulated, “redundant” systems with multiple backups to safeguard our environment now and in the future.

When we understand how natural features and human interventions protect the environment and drinking water around carbon storage, we realize this technology can safely make energy more sustainable.

“The injection of CO2 itself is not a new technology. Commercial CO2 injection has been occurring for over 50 years and began in Louisiana in 1983,” according to Mike Alletag Director of CCUS at CapturePoint, a company developing plans for storage at the CENLA Hub in Central Louisiana.

Safety precautions have improved over the last five decades, in line with frequently updated regulations, meaning the CENLA Hub would be subject to “the highest regulatory threshold for any well in history,” Alletag says.

Depth and time protect water

To protect drinking water, the U.S. Geological Survey (USGS) stipulates carbon storage facilities must be at least 3,000 feet beneath the surface—far below underground drinking water sources, which have a median depth of around 150 feet. This requirement also guarantees the best temperature and pressure for storing carbon in a stable manner, according to the Department of Energy.

Water safety is checked with two separate monitoring wells per Environmental Protection Agency (EPA) guidelines. One well is just above the carbon confining zone and one is just below the deepest underground source of drinking water. Continuous measurement of pressure and temperature can identify any fluid migration.

Extensive regulations for each phase of the project include a separate set of EPA post-injection requirements to ensure the underground CO2 plume has stabilized and original pressure has been restored after the well is capped and closed. Monitoring continues during this period, as the stored carbon stabilizes over time and becomes a permanent feature of the subsoil.

“Studies have shown that CO2 can be safely stored underground, such as in deep, porous rock formations, for thousands of years, and we’ve even found natural pockets of CO2 that have existed for millions,” according to European Commission research.

The proposed CENLA Hub project in Louisiana was chosen for its natural advantages, with storage formations ranging from 4,500 feet to greater than 10,000 feet deep. The site also has the salty soil best suited for carbon capture according to the U.S. National Energy Technology Laboratory, and it is capped with natural rock layers, which act as an extra barrier to hold the carbon in place and separate it from the drinking water layer.

Hundreds of regulations

All pipelines that carry CO2 are regulated by the U.S. Pipeline and Hazardous Materials Safety Administration (PHMSA), which mandates 24/7 monitoring and sets extensive requirements regarding how pipes are built, inspected, maintained, and protected with emergency plans. That’s why CO2 pipelines have proven to be far safer than pipes carrying gas or oil.

All carbon storage projects must comply with EPA Underground Injection Control (UIC) Class VI regulations for CO2 injection wells—detailed rules developed to ensure public health and protect drinking water. Class VI regulations include hundreds of additional requirements in the areas of construction, inspection, maintenance, monitoring, and response preparation. Elements of these requirements include:

• Geological standards for the site.
• Design using computer modelling of CO2 plume and underground pressure.
• Strict construction regulations, including several layers of corrosion-resistant, lab tested materials.
• Extensive testing and monitoring of underground pressure and groundwater quality.
• Safe operation procedures.
• Standards for capping the well.
• Maintenance of financial instruments to cover operational costs, including post-injection site care.
• An up-to-date emergency and remedial response plan.
• Reporting of testing and monitoring results to permitting authorities.

Modeling and monitoring

Protections for drinking water and other risks around carbon storage sites are built into the process.

A detailed geologic model of how the stored CO2 will behave at the site is based on data from formation testing, fluid samples, pressure, and temperature data, under EPA requirements. Similar modeling and testing has been used for decades in the oil and gas industry, but with Class VI wells for carbon capture the level of detail and analysis is far more rigorous.

Alletag said monitoring and other safeguards at the CENLA site are designed to meet or exceed exacting government safety standards. Within the injection well and in dedicated monitoring wells, gauges will monitor downhole pressure and temperature continuously, Alletag explains. If the injection pressure gets reaches 90% of the fracture pressure, an automated choke will reduce or stop carbon injection, he says.

Based on a detailed testing plan, surface pressure and temperature at the CENLA site would be monitored continuously to ensure it meets standards set by the Louisiana Department of Energy and Natural Resources.

All carbon storage facilities must also be protected with detailed emergency plans for local emergency responders, who will conduct safety exercises.

Thanks to these, and other constantly updated regulations from a range of government agencies, we can be sure carbon capture offers a safe means for improving our energy independence while protecting our environment.