Some argue that carbon capture, utilization, and storage (CCUS) are critical tools for reducing global carbon emissions, though questions remain about their scalability, cost-effectiveness, and long-term impact. Safe and efficient supercritical or dense-phase carbon dioxide (CO₂) transportation is critical for successfully implementing CCUS projects.
According to the U.S. Department of Energy website, “Carbon capture, utilization, and storage (CCUS), also known as carbon capture, utilization, and sequestration, is a process that captures carbon dioxide emissions from sources like coal-fired power plants and either reuses or stores them so they will not enter the atmosphere.” The CO2 is then compressed and transported through pipelines, roads, or ships to a site for storage.
In a study published in the KeAi journal Journal of Pipeline Science and Engineering, the PipeChina Group from China University of Petroleum (East China) outlines a method for predicting hazard distances following CO₂ pipeline leaks. The team conducted the first full-scale CO₂ pipeline burst fracture tests in China to assess the fracture arrest performance and potential risks associated with such leaks.
Addressing the risks of CO₂ pipeline leaks
“CO₂ leaks caused by pipeline breaks can have consequences more severe than property damage,” explains lead author Prof. Yuxing Li from the Key Laboratory of Oil and Gas Storage and Transportation Safety at China University of Petroleum (East China) in Shandong Province. “Due to the positive throttling effect of CO₂ and the toxicity of high concentrations of CO₂, it can frostbite or even asphyxiate plants and animals in the vicinity of the leakage area. Therefore, studying the leakage characteristics of supercritical and concentrated-phase CO₂ and predicting its potential hazard distance is significant.” The team focused on the leakage characteristics of supercritical-phase CO₂, which presents unique challenges due to the material’s positive throttling effect and high concentration toxicity. They examined the impact of initial conditions, such as temperature and pressure, on CO₂ concentration near and far from the leakage site.
Key findings
The research involved four full-scale burst tests under various conditions to better understand how CO₂ concentration disperses. The team developed and validated a CO₂ concentration diffusion model, integrating these findings into a proposed hazard distance calculation framework.
Prof. Li notes that pipeline leaks have varying consequences depending on factors like temperature and pressure differences along the pipeline, as well as the distance between the leakage point and cut-off valves. “The relative distance between the leakage point and the cut-off valve influences the CO₂ leakage characteristics and, consequently, the delineation of the hazard distance,” explains Li.
Improved prediction using machine learning
The researchers developed a PSO-BP neural network model to address the complexity of predicting hazard distances at various pipeline locations. This machine learning approach aligns with the results of the CO₂ diffusion model while greatly reducing computational time and resource demands requirements.
Implications for CO₂ transport safety
This study emphasizes the necessity of accurate hazard prediction models for ensuring the safety and reliability of CO₂ transport pipelines, a critical link in the CCUS industry. By merging experimental testing and advanced modeling techniques, the researchers provide a framework that could inform risk management strategies for large-scale CO₂ transportation projects.
The future of CCUS
According to the International Energy Agency, carbon capture, utilization, and storage (CCUS) technologies are gaining traction, with approximately 45 commercial facilities currently in operation across industrial processes, fuel transformation, and power generation. Despite slow initial progress, CCUS development has accelerated in recent years, with over 700 projects now in various stages of development.
In 2023, announced capture capacity for 2030 grew by 35%, reaching approximately 435 million tons (Mt) of CO₂ per year. Announced storage capacity saw a 70% increase, totaling around 615 Mt per year. While these figures mark significant progress, they still represent only 40% of the CO₂ capture and 60% of the storage required to meet the Net Zero Emissions by 2050 (NZE) Scenario, which targets capturing and storing 1 gigaton (Gt) of CO₂ annually by 2030.
This growing momentum is a promising step, but further action is needed to meet global climate goals.