What Is Carbon Capture and Sequestration and How Is It Monitored?
Industrial Facility Showing Emissions
Carbon capture and sequestration (CCS) is a vital means of reducing greenhouse gas emissions. It may be humankind's best weapon against climate change.
And, as technology evolves, the CCS market grows.
As of 2020, researchers valued the global CCS market at $4.17 billion. By 2026, they estimate its value will more than double, to $9.42 billion.
Part of this technological evolution concerns CO₂ capture monitoring technology. Monitoring mitigates risks associated with carbon storage, and it makes long-term sequestration feasible.
In this analysis, discover how CCS works, how new technologies are affecting its impact, and how to develop and implement a CCS monitoring and reporting strategy.
What Is Carbon Capture Sequestration (CCS)?
Carbon capture and storage is a set of processes that reduce or prevent greenhouse gas emissions. It separates out CO₂ prior to—or during—fuel-burning processes.
Then, engineers transport and store the separated carbon in a carbon pool.
A carbon pool is typically underwater or underground. The pool sequesters the fluid, keeping it from contaminating the atmosphere. Some CCS projects aim to store carbon in a space where genetically modified plants can transform it.
Currently, most projects store carbon by injecting it into depleted oil and gas wells, saline formations, or unusable coal beds. These are geologic sequestration tactics.
Modes of Carbon Capture
There are two primary modes of carbon capture: pre-combustion and post-combustion. Oxy-fuel capture is a sub-type of pre-combustion capture. Most carbon capture technologies rely on one of three key separation mechanisms:
Advanced solvents
Sorbents
Membranes
Industrial carbon capture systems currently absorb CO₂ compounds with a carbon dioxide scrubber. Scrubbers use amines to absorb CO₂, which makes the device a sorbent.
Pre-Combustion Capture
Pre-combustion capture utilizes a controlled gasification reaction to oxidize fossil fuel. This enables combustion in an oxygen-saturated environment. The gasification reaction chemically decomposes the fuel, which creates syngas.
Engineers then process that syngas through a water-gas shift reactor (WGS). That process converts carbon into CO². It also increases the concentration of both CO₂ and H₂ in the system.
Using a separation technology, engineers divide the CO₂ and H₂. Some processes then use the H² for fuel. Certain advanced turbine systems and NETL fuel cells already utilize H₂ derived from this process.
After processing, developers can store the segregated CO₂, which is already contained.
Post-Combustion Capture
The best applications of post-combustion capture methods are natural gas and pulverized coal (PC) power plants.
The exhaust produced by these power generation methods is a gaseous waste. Specifically, it's a mixture of N₂ and CO₂. Post-combustion capture methods separate the CO₂ from this gas stream before it enters the atmosphere.
Today, most post-combustion capture utilizes chemical solvents with amines. Chemical looping combustion is another proposed post-combustion capture technology. Foundations have launched projects researching this technology.
Carbon Dioxide Removal (CDR)
Scientists are currently researching and developing carbon dioxide removal (CDR) strategies. These techniques can remove CO₂ from the atmosphere after it has already been released.
One technology in development is direct air capture (DAC). DAC uses sorbent filters to bind with CO₂ molecules, pulling them out of the air. Or, it may use liquid solution filters.
Once the carbon is captured, engineers plan to store and sequester it. No matter how the carbon is captured, storage methods are similar.
How Does Carbon Capturing or Sequestering Work?
CCS can be divided into two distinct processes: capturing and storage.
Carbon capture technologies are means of separating carbon from the gas or liquid it's mixed with. Once separated, the carbon is contained for transport and storage.
Carbon capture storage technologies enable engineers to inject carbon deep underground or store it safely in a biologic process.
For an overview of contemporary separation technologies, read "Carbon Capture and Storage: The Way Forward." Researchers published this 2018 report in the journal Energy & Environmental Science.
It offers a clear breakdown of contemporary carbon separation methods.
Sequestration vs. Storage
Carbon capture sequestration (CCS) describes the complete process of separating, transporting, and storing carbon. Carbon capture storage only refers to the last step of this process.
Engineers often use the two terms interchangeably.
CCS Mechanisms
Developers have proposed a wide variety of carbon storage mechanisms and tools. These technologies include:
Geo-sequestration
Algae/bacterial metabolization
Mineral storage (carbonate formation)
Geological sequestration is the most utilized method so far. Engineers pressurize the separated carbon into supercritical fluid (SCF) form. Then, they inject the fluid carbon deep underground.
It's theoretically safe to store the carbon in coal seams, under saline formations, beneath oil fields, or in basalt formations. In some circumstances, the carbon remains a liquid due to intense pressure.
Why Is Monitoring Critical?
CO₂ capture monitoring is necessary to mitigate risks inherent to carbon storage. International environmental scientists identify four key risks inherent to geo-sequestration. Risks include:
Contamination of drinking water
Pressure buildup
Hydraulic fractures
Leakage
To prevent these adverse effects, the United States Environmental Protection Agency (EPA) requires carbon capture companies to monitor storage sites.
Monitoring must include tracking plume migration. Companies also need to observe:
The pressure inside and above the storage reservoir
Induced seismicity
Secondary trapping mechanism extension
Chemistry of local freshwater aquifers
EPA: Greenhouse Gas Reporting Program (GHGRP)
In the United States, carbon storage companies must report the monitoring data through the EPA's Greenhouse Gas Reporting Program (GHGRP).
The GHGRP tracks emissions from large sources, including industrial facilities and fuel and gas suppliers. Each October, the EPA compiles the data it gathered and publishes it in a public document.
Monitoring, Verification, Accounting (MVA)
The national Carbon Storage Program supports monitoring, verification, accounting, and assessment research.
This systematic approach helps organizations determine the parameters for safe carbon storage across many variables. With these parameters knowns, engineers can develop better tools to strengthen our carbon storage capacity.
These tools will then make carbon storage more accessible and less expensive as technology evolves. Ultimately, information gleaned through monitoring serves the DOE's Carbon Storage R&D program.
CO₂ Capture Monitoring: Overview
As of 2022, MVA has catalyzed the development of four categories of monitoring tools. The categories are:
Subsurface monitoring
Tracer (near-surface) monitoring
Surface and atmospheric monitoring
Intelligent monitoring system (IMS) networks
Seismic monitoring is an indirect, subsurface monitoring method. Recent analyses note that remote monitoring tools have proven successful for many carbon storage sites.
Carbon Capture Seismicity Monitoring
Injection-induced seismicity is a risk inherent to underground carbon sequestration. Injecting carbon can trigger a chain reaction that causes faults to rupture.
Monitoring mitigates the risk of induced seismicity. It also alerts teams to any seismic activity for protection.
Induced Seismicity Monitoring
Geologists first invented seismic monitoring tools to track volcanic activity. Monitoring seismic waves—energy that travels through layers of the earth—can determine the probable state of a volcano.
A volcano may be restful, restless, pre-eruption, or actively erupting.
Similar strategies make it possible to predict the likelihood of earthquakes or other disruptive movements post-carbon injection.
Microseismic Monitoring
Microseismic monitoring tools track vibrations to observe seismic activity. To use these tools, researchers choose either downhole, ground, or mixing monitor strategies.
Typically, researchers conduct microseismic monitoring with multiple accelerometers. These tools specifically record the acceleration of a body in its rest frame.
With three-axis accelerometers, developers can passively track minute variations in seismic activity.
Microseismic monitoring is typically temporary. It records changes in seismic activity over a period of a few months.
A permanent microseismic monitoring system faces technological challenges.
CCS Monitoring Methods and Tools
Developers can approach CCS monitoring with a variety of methods and tools. Methods include the seismic monitoring options outlined above. Most of these methods fit into one or more international regulatory frameworks.
Iterative approaches emphasize both storage site selection and monitoring. As developers monitor the storage area, experts recommend they continually re-assess in light of new risks.
One strategy to tackle monitoring is CO₂ plume tracking and traping. This strategy focuses on preventing harm to the environment surrounding stored carbon by managing plumes of CO₂ that escapes sequestration.
Tools
Geologists often use seismic and electromagnetic data. The evolution of sensor technology has improved this data acquisition. Research that utilizes distributed fiber optic sensing shows promise. Other current or developing sensing technologies include:
Distributed acoustic sensing
Deployed geophone network
CO₂ detection satellites
One recent study utilized these data sets in combination to estimate CO₂ saturation in a storage site. Beyond that, researchers are finding new ways to cultivate predictive models for ccs.
Predictive Modeling
Researchers at the University of Oslo applied a rock physics model to CCS monitoring. This model let them develop time-lapse predictions of a CCS storage site. It modeled plume delineation, saturation, and pressure changes for the next 40 years.
Los Alamos National Laboratory sought to develop AI software to strengthen the accuracy of these predictive models. The AI weighs both environmental and economic risk factors.
With this new tool, researchers hope to make ccs viable and broadly affordable. Currently, the AI—SimCCS—has mapped out a handful of subterranean regions in the United States.
SCADA
Another tool developers may utilize is an Intelligent Monitoring System (IMS).
IMS uses Supervisory Control and Data Acquisition (SCADA) software to analyze dynamic measurements. These programs can analyze current readings against a massive stored dataset.
In the past, SCADA has assessed risks inherent to irrigation and installing storm pumps. Now, the technology can move CCS forward.
Seismicity Monitoring Support and Stages
There are three stages in which seismicity monitoring support is critical.
First, during the development of a proposed carbon sequestration project, project leaders must gather relevant seismic data. Without this information, the EPA and state agencies will not approve a project.
The American Carbon Registry has published the official, approved methodology for carbon sequestration projects. The method encompasses the precise way to quantify and monitor both emission and storage metrics.
CCS projects must adhere to the monitoring, reporting, and verification (MRV) framework.
This framework guides project managers through the implementation and reporting stages of the project. CCS teams must make reports annually, initially. Then they must make reports every five years.
Seismic activity that indicates elevated risk must be addressed and remediated.
The final stage is the long-term monitoring phase of the project. Long-term monitoring may require different monitoring tools and systems. Organizations may wish to upgrade monitoring equipment as technology evolves.
Development
Development is a complex process. It's common for carbon capture companies to partner with geological specialists to develop a legal ccs plan.
Specialist geological consultants can use high-precision tools to predict viable storage locations. They further enable organizations to meet all regulatory guidelines.
Data Gathering (Seismicity Surveys)
Seismic surveys gather information about subterranean geological structures. This indicates whether a given geologic location is a good candidate for carbon storage.
Seismicity surveys can indicate high-risk density changes and structures that can disqualify a location from sequestration.
At the same time, baseline readings enable engineers to interpret seismic information gleaned in later stages accurately.
Well Implementation (Considerations)
Organizations may consider using Class VI wells for carbon sequestration. Class VI wells must meet strict site characterization requirements, to protect drinking water.
In 2010, the EPA passed the Final Rule, which controls risks stemming from geologic CO₂ sequestration in Class VI wells. Support services can enable organizations to review and meet the criteria mandated by the Final Rule.
Submit Monitoring Plan
Once engineers have developed an evidence-based plan, it's time to submit it to the EPA. The EPA hosts instructions on submitting a geologic carbon sequestration plan on its GHGRP page.
Developers may also submit the project to the American Carbon Registry at that time.
Implementation, Reporting
Continued monitoring is critical as developers execute their ccs plan. Plume migration and leak detection can alert engineers to high-risk situations at this critical juncture.
Monitoring likewise ensures engineers deliver the carbon to the storage target accurately during injection. Carbon capture sequestration well monitoring requires specific solutions compatible with the geology of oil wells.
After injection, frequent seismicity monitoring is crucial. Independent verification ensures developers their strategy is safe.
Long-Term Monitoring, Annual Activities
The purpose of a geologic storage complex is to contain sequestered carbon long-term. Long-term monitoring ensures the storage complex remains impermeable for decades.
Developers can accomplish long-term monitoring and annual reporting activities with a variety of tools and methods. Geological support services can recommend technologies and methods best suited to a given CCS project.
Carbon Capture Sequestration Solutions
Carbon capture sequestration is the future of energy. CO₂ capture monitoring is a critical part of any CCS solution.
At ISTI, our seismologists are innovators in this evolving field. With our expertise, we've enabled developers at the Illinois Basin-Decatur Project (IBDP) to meet EPA regulations.
Our CCS monitoring solutions empowered this first-of-its-kind project to safely store large amounts CO₂ in the USA.
What monitoring solutions can we create for you?
Contact us today to learn more.