Frequently Asked Questions
What is CCS?
Carbon capture and sequestration, or CCS, is the process by which CO2 is separated from hydrocarbons in fossil fuels such as coal, natural gas, or petroleum coke, a byproduct of the oil refinery process, and then sequestered deep underground. CO2 separation can be accomplished through a chemical gasification process prior to combustion in what is called pre-combustion capture. Pre-combustion capture involves exposing the fossil fuel to oxygen and water at high temperatures, which results in the extraction of hydrogen and CO2. This extraction and capture can also occur during or after the burning of fossil fuels.
Once “captured,” CO2 is compressed to a near liquid state and transported via pipeline to sequestration deep underground, far below water tables and usually below nonporous cap-rock. Ideal geological formations for sequestration include depleted oil and gas fields and deep saline formations, where oil, gas, or saline has been sequestered naturally for millions of years.
Pre-combustion capture has the additional benefit of producing hydrogen, a “clean fuel” that can be used as fuel for a power plant, cars and other industrial uses.
What is CO2?
CO2, or carbon dioxide, is a non-toxic and otherwise harmless gas that we breathe in and out every day. It is one of the elements that nourish plant life in the photosynthesis process. Food grade CO2 is found in carbonated drinks and is used in the flash-freezing process. It is also the primary ingredient in baking soda and fire extinguishers.
However, CO2 is also believed to be a major contributor to global warming resulting from human activity since the dawn of the Industrial Age. It is produced through industrial processes that involve burning of any fossil fuel and through chemical processes that separate it from other mineral states. And like any gas (including oxygen) that is found in too high a concentration without ventilation, CO2 can cause asphyxiation.
In recorded history there have been rare, natural occurrences of high volume CO2 releases from seismic or volcanic activity that have caused asphyxiation. However, these instances had nothing to do with carbon sequestration nor are the circumstances under which they occurred similar to those for carbon sequestration.
Is CO2 sequestration safe?
Documented facts from hundreds of well-researched geologic studies conclusively demonstrate that CO2 sequestration is safer than many other industrial processes. CCS projects proposed in California plan to sequester CO2 beneath non-porous cap rock where it is expected to remain for millions of years — as long cap rock has held oil and gas reservoirs in place.
A CO2 pipeline is very similar in operation to other gas and liquid pipelines already in widespread use throughout the world. Since CO2 is not flammable, there is no danger of fire, but compressed gas is under pressure and could displace displace oxygen in small, enclosed spaces. These factors require safety technologies, including electronic monitoring devices placed throughout the entire length of the pipeline that can instantly pinpoint leaks and automatically isolate the area and shut off the pipeline.
Once available, a CO2 pipeline infrastructure can also be used to transport and sequester CO2 that currently vents into the atmosphere from other sources, such as methane gas recovery and other industrial processes.
How does CO2 stay underground through sequestration?
Carbon dioxide can be sequestered in different ways. When CO2 is compressed it can be injected via deep wells into oil and gas production zones deep underground. Under layers of impermeable “cap rock,” oil and gas has been held in porous rock reservoirs for millions of years. As the oil and gas is produced, it travels through the porous rock to a well and then to the surface, essentially freeing space between the grains of rock where CO2 can be injected to replace the produced oil and gas.
Another option is to pump CO2 into saline aquifers where it dissolves in salty water, just like sugar dissolves in tea. The water with CO2 dissolved in it is then heavier than the water around it (without CO2) and so it sinks to the bottom of a rock formation, trapping the CO2 indefinitely. Another form of sequestration takes place when CO2 reacts with the minerals in the surrounding rocks and forms new minerals on the rocks, much like shellfish use calcium and carbon from seawater to form their shells. Depending on the chemistry of the rocks and water, this process can be very rapid or very slow, but it effectively binds the CO2 to the rocks.
Why is CCS such an important technology?
Today, much of the world’s economy runs on fossil fuels. In developing countries like China and India, fossil fuel usage is expanding significantly with no carbon mitigation plans. In China alone, two coal-fired power plants go on line every week. This fossil fuel power expansion needs to change, and we need to reduce our reliance on these fuels. However, while policymakers, scientists and consumers begin our transition to new, renewable sources of energy, as well as adopt conservation and efficiency measures to reduce the use of traditional energy sources, we also must take action to reduce CO2 emissions from conventional sources of energy.
Carbon capture and sequestration is a critical tool in the effort to reduce the concentration of global warming gases in the atmosphere. Most experts agree that pursuing this viable, safe and proven means of addressing global warming is essential to the development of a comprehensive strategy to successfully confront the most serious environmental issue of our time.
Where is CCS currently in use?
CCS has been in use for over 40 years in the oil and gas industries as a way to enhance oil and gas recovery. Permanent sequestration of CO2 has been used in Sleipner, Norway since 1996, Weyburn, Canada since 2000, and in Salah, Algeria since 2004—all without incident.
CO2 sequestration at Sleipner, Norway off-shore platforms