Myths and facts about CO2 storage

This is the second article in a series of five about storage. You can read the previous article, An Introduction to Storing CO2 Underground, here. Article number three will cover global views on CO2 storage.

What a lot of people do not know is that one of the first storage projects was established as early as in 1979 in Lubbock, Texas, and others have been running since the mid-80’s without any major incidents. This means that CO2 has been successfully stored underground for more than 30 years.

But what are the potential threats from CO2 storage that people fear?

Leaks and blowouts

The main concern about CO2 storage is leaks and sudden blowouts of CO2. The fear is that a sudden increase of CO2 in the air can have severe and even fatal consequences for people who live close to storage sites. There have been catastrophic occurrences of outgassing from natural CO2 sources, and these events are sometimes used to illustrate the potential threats of carbon storage.

The most famous and severe event was what happened at Lake Nyos in Cameroon. CO2 from a magma chamber underneath the earth seeped up in the lake, charging the water with vast amounts of CO2. In 1986, a sudden lake overturn caused thousands of tonnes of CO2 to be released simultaneously and the local topography caused the CO2 to be trapped and to move swiftly down a valley, killing 1700 people and 3500 livestock.

Gruesome events like these will undoubtedly seem frightening, but it is important to remember that one would not choose to store CO2 in a place like Lake Nyos. There are plenty of better alternatives in places where the topography will not concentrate and move the CO2 like in the Lake Nyos incident.

A more realistic scenario, should an event occur that allows the CO2 to seep out of its storage, is far less dramatic. The CO2 is not concentrated like a big bubble about to burst under the surface of the earth, but is stored in a dense phase in tiny pores underground. A crack, for example caused by an earthquake, could allow the CO2 to seep, but it will, if stored under the ocean, blend with the seawater and slowly be transported to the surface. Once it reaches the surface it will be blown with the wind and diluted into harmless amounts.

Storage sites are also carefully and continuously monitored, and any changes in the storage conditions will quickly be registered.

Storage sites are also carefully and continuously monitored, and any changes in the storage conditions will quickly be registered. There is continuous research being done on different kinds of monitoring techniques that can be adapted to various storage conditions, and also to lower costs and add more automatic monitoring. According to CO2geonet, one can safely monitor storage sites with the technology we have available today.

Another aspect to take into consideration is that CO2 already exists in the nature around us. Humans did not invent underground storage of CO2. There are hundreds of natural CO2 reservoirs around the world that have kept the CO2 locked up for millions of years. This, in addition to the experience we have from newer storage sites, show that geological formations are capable of locking up CO2 for a very long time.

Drinking water

A lot of local opposition against carbon storage is based on the fear of CO2 leaking into the drinking water. Studies have shown that there is some leakage into drinking water. CO2 is water soluble under pressure, and as soon as the right amount of pressure is gone, it will try to escape the water (like the bubbles in carbonized water.) Small amounts of CO2 in water is not harmful at all, most of us actually enjoy a glass of carbonated water quite frequently. But a leak from a CO2 reservoir can increase the amount of CO2 in the water to above the maximum contaminant levels. Researchers are still investigating the possible impacts of contaminated drinking water.

Another worry is displacement of water, which means injecting CO2 into reservoirs or porous rocks will move the water that is already there. This can either add pressure to the existing reservoir or move the water into drinking water reservoirs. Using various kinds of pressure management can control the increased pressure, but the only way to avoid displacement of water into drinking water reservoirs is to make sure that the CO2 is injected in areas situated far away from human drinking water.

The most obvious way to avoid pollution of drinking water is to inject the CO2 in storage areas in the ocean or other places far from human drinking water sources. There is a vast amount of available storage areas, so there is no reason not to avoid fresh water reservoirs that are being used for drinking water.

Earthquakes

There is also a fear that human activity underground can create earthquakes. Human activity has triggered earthquakes, especially from oil and gas extraction, so it is only natural to questions whether or not carbon storage can result in earthquakes too. No known “manmade” earthquakes are the results of CCS or EOR operations that inject CO2. Reports also state that even though there have been earthquakes related to similar types of fuel removal or injection underground, these events can easily be controlled by using various techniques to keep the balance of fuel injected and withdrawn.

A special report from the Intergovernmental Panel on Climate Change states that:

“Observations from engineered and natural analogues as well as models suggest that the fraction retained in appropriately selected and managed geological reservoirs is very likely to exceed 99% over 100 years and is likely to exceed 99% over 1,000 years.

For well-selected, designed and managed geological storage sites, the vast majority of the CO2 will gradually be immobilized by various trapping mechanisms and, in that case, could be retained for up to millions of years. Because of these mechanisms, storage could become more secure over longer timeframes.

For well-selected, designed and managed geological storage sites, the vast majority of the CO2 will gradually be immobilized by various trapping mechanisms and, in that case, could be retained for up to millions of years. Because of these mechanisms, storage could become more secure over longer timeframes.”

With all the knowledge with have from natural carbon storage and manmade storage sites, and considering how closely the sites are monitored and how CO2 reacts with its surroundings should it leak, it is safe to say that carbon storage underground is safe.