Brief Carbon Capture, Utilization, and Sequestration

Introduction

Carbon capture, utilization and storage is the process of capturing carbon dioxide from a large point source such as a power plant or industrial facility, and repurposing or storing the carbon dioxide deep underground for long-term storage.  

The U.S. Department of Energy has identified the process as a method of carbon management that addresses legacy emissions as well as new carbon emissions. As such the DOE through the Office of Clean Energy Demonstrations announced $2.5 billion in funding to accelerate the deployment of these carbon management technologies.  

CCUS is set to become more integrated into the U.S. energy system and will provide states another tool to manage carbon dioxide emissions with 25 states introducing 88 bills regarding CCUS measures in 2024. Many states continue to pursue CCUS systems, particularly given the Environmental Protection Agency's recent move to establish carbon capture rules for coal and gas plants beginning in 2032, as well as the DOE’s numerous funding streams to advance the technology.  

Despite the increased attention CCUS has received, cost barriers continue to slow the deployment of projects. The International Energy Agency has determined the cost to capture carbon specifically can vary extensively. Industrial processes producing highly concentrated carbon streams can vary around $15 to $25 per ton of carbon dioxide, to $40-$120 per ton of carbon dioxide for processes with more diluted streams such as power generation. Governments to date have committed $4.5 billion to CCUS projects worldwide to help lower these costs.  

This brief will highlight the various methods of carbon dioxide capture, how captured carbon can be used or sequestered, and provide an overview of a variety of state level policies impacting CCUS.  

How Carbon is Captured

There are two primary forms of carbon capture technologies at varying stages of commercial readiness: 

1. Point-Source Capture, and
2. Direct Air Capture.

Point-source capture

PSC refers to when carbon dioxide is directly captured at the point of emission. This can include sources of power generation and industrial sources where carbon dioxide is captured at the plant’s flue gas or syngas stream. To separate the carbon dioxide from other gases power plants and industrial facilities can use a post-combustion, pre-combustion, or oxy-fuel combustion cycle that removes carbon dioxide at different intervals in the process. Once the carbon dioxide has been removed it can be added into sorbents (solid carrier), solvents (liquid carrier) or permeable/semi-permeable membranes with various applications for each method. PSC remains the most commercially ready technology with 16 operational sites across the United States and another nine facilities under construction.  

Direct Air Capture

DAC is a similar process to PSC in that it requires either a solid sorbent system or a liquid solvent system that extracts carbon dioxide molecules for storage. However, DAC systems are not connected to power stations or industrial facilities but instead capture carbon dioxide directly from the ambient air. Once captured temperature, pressure, and/or humidity is applied to extract individual carbon dioxide molecules to be used or sequestered for long-term storage. DAC systems are not as commercially available as PSC in part because they require more energy to remove carbon that is more diluted in the ambient air and subsequently increases the cost to operate the system compared to more conventional PSC. DAC is actively being advanced by companies around the United States with the DOE providing $3.5 billion in funding to advance and demonstrate the technology.  

Marine Carbon Dioxide Removal  

While PSC and DAC are the most researched and deployed carbon management systems, the DOE and National Oceanic and Atmospheric Administration have identified marine carbon dioxide removal as an area with high potential for development and expansion. Recently, the DOE announced $36 million for 11 projects across eight states to develop and advance this nascent field. Principally, areas within the outer continental shelf in the Atlantic Ocean possess numerous saline reservoirs and depleted gas fields that are prime for long term carbon storage.  

Utilization

Carbon dioxide has effectively been used in enhanced oil recovery for decades. One of the primary uses of carbon dioxide has been pumping the gas back into active oil reservoirs resulting in 20% to 40% recovery of the original oil. Additionally, the reservoir can also function as long-term storage for carbon dioxide. 

While carbon dioxide can be used directly in the process of oil recovery it can also be transformed into solid carbonates in a process called mineralization. When converted into a carbonate in the solid form, the carbon dioxide can be used in aggregates for marketable products such as concrete, asphalt, and construction .  

Sequestration

Sequestration refers to the storage of carbon dioxide after it is captured. The DOE differentiates storage between biological and geological storage. Biological refers to storage through forest and grasslands, and geological refers to storage deep underground in oil and saline reservoirs. A quarter of a billion tons of carbon dioxide have already been stored globally, and the DOE has invested $775 million for over 100 projects across the country to support advancement and deployment of large-scale storage methods. Carbon dioxide can be transported through a variety of methods including pipelines, trucking or freight, to various reservoirs or basins. When carbon dioxide is stored underground it reacts with minerals already in the geological formation, which prevents the carbon dioxide from being released back into the atmosphere after it has been stored.  

State Policies

There are a variety of state actions involving CCUS. One example is state “primacy” over Class IV wells (meaning they have authority over permitting decision making) that are used for carbon dioxide sequestration. Three states currently hold primacy over all the wells in their state: Louisiana, North Dakota and Wyoming (West Virgina’s application for primacy is pending). Having primacy over Class VI wells allows states to approve sequestration projects on a faster timeline than the EPA. Numerous states began implementing CCUS laws in 2007-2009 including Illinois, Kansas, Louisiana, and North Dakota. There are also a variety of other state policy examples that touch on several key aspects of CCUS.