There are approximately 8,500 kilometers of carbon dioxide (CO2) pipelines in the United States today, primarily in place to serve the enhanced oil recovery (EOR) market. In 2021, researchers from Princeton University analyzed five pathways to achieve net zero carbon emissions by 2050. Expansion of carbon dioxide capture, transport, usage and storage was identified as a requirement for each pathway with one pathway forecasting a need for approximately 106,000 kilometers of carbon dioxide pipeline by 2050. The study acknowledged the challenges of permitting all infrastructure projects, but did not discuss the importance of pipeline safety with respect to permitting carbon dioxide and transport and storage projects.

The construction and operation of carbon dioxide pipelines in the U.S. date to the 1980s and have been subject to manageable permitting challenges and characterized by few accidents. On Feb. 22, 2020, however, a pipeline transporting supercritical carbon dioxide ruptured near Satartia, Mississippi, resulting in the release of approximately 31,400 barrels of carbon dioxide (approximately 3,640 metric tons) requiring the evacuation of approximately 200 residents and sending 45 individuals to the hospital for treatment. Excluding the Satartia accident, over the 10-year period from 2010 to 2021, 66 accidents on pipelines transporting supercritical-phase carbon dioxide have been reported to the Pipeline Safety and Hazardous Materials Administration (PHMSA). The average release of carbon dioxide for these 66 accidents was 920 barrels (approximately 110 metric tons) and no accident resulted in fatalities or injuries regarding hospitalization. The Satartia accident dwarfed the historical average by more than 30-fold, a troublesome statistic considering the of importance carbon capture, utilization, and storage (CCUS) with respect to net zero goals.

The magnitude and severity of the Satartia event gained national attention and prompted PHMSA to undertake a deliberate approach to regulate carbon dioxide pipeline safety in the U.S. PHMSA investigated the Satartia carbon dioxide pipeline and reported the issues leading to the pipeline failure and the problems associated with prompt response to the incident. Based on those findings, on April 8, 2022, PHMSA issued a rule requiring new or reconstructed carbon dioxide pipelines to install remote or automatic shutoff valves in rare instances of pipeline failure. PHMSA then scheduled a meeting in Des Moines, Iowa, from May 31 through June 1, 2023, to obtain public comment on carbon dioxide pipeline safety. After analyzing both the PHMSA Failure Investigation Report for the Satartia accident and public comments, PHMSA submitted a notice of proposed rulemaking (NPRM) for carbon dioxide pipelines to the Office of Management and Budget for review on February 1, 2024. On January 10, 2025, PHMSA issued a Notice of Proposed Rulemaking (NPRM) for carbon dioxide pipelines.

The NPRM, although withdrawn by presidential executive order, remains instructive about the future regulation of carbon dioxide pipelines in the U.S. In summary, the proposed regulations would have modified regulations found at 49 CFR 195 (Transportation of Hazardous Liquids by Pipeline) governing highly volatile liquids (HVLs, including carbon dioxide) in 18 areas, 16 of which are directly related to carbon dioxide pipelines as summarized below:

1. The definition of carbon dioxide would have been amended to (1) include not only supercritical-phase carbon dioxide but also carbon dioxide in the gas and liquid phases, and (2) lower the threshold of carbon dioxide molecules present in the product stream (in any phase) necessary for a pipeline to be considered a “carbon dioxide” pipeline subject to greater than 50% of the molecules in the product stream.

2. Operators of carbon dioxide pipelines would have needed to perform vapor dispersion analyses to determine whether a release from their pipelines “could affect” a high consequence area (HCA) and would therefore be subject to integrity management program requirements. If the pipeline operator determined that its pipeline could affect an HCA, it would have been required to install fixed vapor detection and alarm systems and consider installation of emergency flow restricting devices.

3. In excavated trenches, operators of regulated pipelines would have had to have instruments and tools capable of detecting hazardous concentrations of hazardous liquids, carbon dioxide, and any known deleterious constituents in the product stream. This proposed rule would have also required carbon dioxide pipeline operators to provide equipment, instruments, tools and materials that might be used in the event of an emergency on a carbon dioxide pipeline to local emergency response organizations and train them on their proper use.

4. Onshore carbon dioxide pipeline operators would have been required to communicate with affected entities (including, but not limited to the public) during a carbon dioxide pipeline emergency as soon as practicable during an emergency.

5. Carbon dioxide pipelines constructed, replaced, relocated or otherwise changed after the effective date of the regulation would have required enhanced design to mitigate fracture propagation through the pipe.

6. All spike hydrostatic testing requirements would have been consolidated in a single section. Additionally, new hydrostatic pressure testing requirements would have been established.

7. Carbon dioxide would have been removed from the list of acceptable test mediums for spike hydrostatic testing.

8. Enhanced conversion to service requirements for pipelines converted to carbon dioxide service would have been established.

9. Enhanced right-of-way surface condition inspection requirements would have been established to require carbon dioxide pipeline operators to look for indicators of leakage from the pipeline, geologic hazards in the area that could affect the pipeline, nearby construction activity, areas of reduced depth of cover, and any other factors that may affect safety and operation.

10. An additional depth of cover classification for agricultural areas would have been established requiring regulated pipelines to be installed so that the cover between the top of the pipe and the ground level, roadbed, river bottom or underwater natural bottom would comply with a minimum depth of 48 inches for normal excavation in agricultural areas.

11. Leak detection systems would have been required for carbon dioxide pipelines built, replaced or relocated after the effective date. Carbon dioxide pipelines existing on the effective date of any final rule would have had four years from that effective date to implement leak detection system requirements.

12. Fixed vapor detection and alarm systems would have been required at each pump station, compressor station, meter station and valve station.

13. Carbon dioxide pipeline operators would have had to consider deleterious constituents (e.g., water and hydrogen sulfide) for assessment scheduling, information analysis and risk analysis.

14. Carbon dioxide pipeline operators would have had to establish a monitoring and mitigation program for constituents within carbon dioxide product streams that can affect corrosion, including microbes, water, oxygen, methane, hydrogen sulfide, carbon monoxide, sulfur oxides, and nitrous oxides.

15. The distance-based reporting exception for safety-related conditions would have been eliminated.

16. Carbon dioxide pipeline operators would have been required to establish emergency planning zones extending two miles on either side of their pipelines to enable operators to adequately identify those community members requiring emergency response information.

The Satartia event galvanized both pipeline and CCUS opponents who have been able to swiftly and systematically challenge carbon dioxide pipeline safety. The efforts of these groups have significantly contributed to Navigator CO2 Ventures’ decision to terminate its Heartland Greenway pipeline and to Summit Carbon Solutions’ decision to suspend carbon dioxide pipeline efforts in South Dakota. The Navigator pipeline would have collected carbon dioxide from ethanol plants in Illinois, Iowa, Minnesota, Nebraska, and South Dakota for storage underground at Mt. Simon sandstone formation in central Illinois. The Summit pipeline was designed to collect carbon dioxide from biofuel plants in Iowa, Minnesota, Nebraska, North Dakota and South Dakota for deep underground storage in North Dakota.
The Pipeline Safety Trust, a nonprofit public charity promoting pipeline safety through education and advocacy, reviewed the proposed rule favorably noting that it had incorporated many of the lessons learned from the Satartia accident. It criticized the proposed rule for not including a requirement for an odorant in carbon dioxide pipelines and for not including performance standards for leak detection equipment.

Unfortunately, the advancement of this rule has been delayed. The public comment period would have drawn comments from carbon dioxide pipeline operators, carbon dioxide pipeline and CCUS opponents, and CCUS advocates and resulted in a rule intended to protect the public while allowing the advancement of carbon capture pipelines and storage reservoirs. In the absence of carbon dioxide pipeline safety regulations, pipeline and CCUS opponents control the narrative. As advocates for safe, reliable and full-scale CCUS, we must engage our elected officials to direct PHMSA to return its attention to carbon dioxide pipeline safety and build on the solid work it has already done.

References available upon request.

Author:
David Elam, TRC Companies
delam@trccompanies.com
919-967-0500

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