Frequently asked questions

What is CCS?

How is CO2 captured?

How is CO2 transported?

How is CO2 stored?

I've heard CO2 can be stored in water too. How does that work?

Why do we need CCS?

Is CCS safe?

How do we know that it won't leak?

But what if there is a leak?

Can CO2 storage sites explode?

But what about blow-outs?

Can CCS remove all CO2?

What does it cost?

Will energy prices rise?

Is there enough room to store it all?

Isn't it better to just stop using fossil fuels?

Isn't CCS just leaving our problems for future generations to look after?

 

What is CCS?

CCS is short for carbon capture and storage. It is a process where CO2 emitted from large stationary emission sources such as fossil fuel power plants or oil refineries, is captured and stored safely underground. This stops the CO2 from being emitted into the atmosphere and is therefore an efficient way of combating global warming. Read more about CCS

How is CO2 captured?

There are several different technologies available for capturing CO2 from industrial flues. Some of them are tried and tested technologies that have existed for decades or longer already. Others are still in a small or large scale testing phase, while a few are only at the experimental stage yet. The most developed technologies are already in full scale use many places and require no further testing or development to be fully suited for CCS projects. Read more about CO2 capture

How is CO2 transported?

The preferred way of transporting CO2 is by pipeline.  Transporting CO2 is already being done extensively, so this is well established as a safe and reliable way to do it. However, if the distance to the storage site is very far, transport by ship may be an option. This would be done in much the same way natural gas is transported by ship today, with the major difference being that unlike natural gas, CO2 is not a flammable gas, so CO2-transport is safer.

How is CO2 stored?

There are several types of storage sites available that are well suited for CO2 storage. The most important characteristic of a good geological storage site, is the presence of porous rock in which the CO2 can be stored (much like water is held in a sponge), and a layer of solid rock that CO2 cannot travel through on top. Read more about CO2 storage

I've heard CO2 can be stored in water too. How does that work?

Yes it is possible, but we don't think it's a good idea. It has been suggested that CO2 can be stored by injecting it into the oceans at great depth. The CO2 will dissolve in the water, and therefore it is kept out of the atmosphere for a while. However, this is not permanent storage. Over time, nature will create an equilibrium between the CO2 stored in the ocean and the CO2 in the atmosphere. The oceans will therefore release excess CO2 into the air, and the CO2 will only be sequestered for a few hundred years at best. This would be to push our problems onto future generations.

Also, CO2 storage has some very serious environmental consequences. When CO2 is dissolved in water, the water becomes more acidic. This is very detrimental to many aquatic life forms.

Why do we need CCS?

Global warming is one of the greatest challenges humanity has ever faced, and urgent measures are necessary to stop it from happening.

There is a lot we can do to stop global warming. We need to replace as much fossil energy as possible with renewable alternatives, and we need to replace fossil fuels in our cars with renewable fuels. We have to stop cutting down rain-forests, too, and we need to conserve energy. In addition to this, we need to capture and store CO2.

The most important reason why we need CCS is that fossil fuels deliver so much of the energy we use today, that it will take many decades to replace it all with renewable alternatives. Also, the energy demand will become even bigger in the future, as the global population grows and more people leave poverty, demanding more of the commodities we are used to in the richer parts of the world.

Also, there are some emissions that can't be removed any other way. The production of cement, steel and chemicals such as ammonia emit large quantities of CO2. There is no known way to remove all these emissions, other than CCS. Read more about why we need CCS

Is CCS safe?

In short: yes. CO2 is an nonflammable gas with low toxicity. When we capture and store it, we do so using many of the technologies that have been developed to handle highly flammable and highly toxic fossil fuels. In other words, CCS involves far less risk than the production of the oil and gas that we rely on as fuels today.

When CO2 is handled and stored correctly, even in a worst case scenario there can be no catastrophic failure. CO2 cannot explode, and while it can't be ruled out that accidents may occur in the injection phase, the emissions would be small and only dangerous in the immediate vicinity of the injection well where the accident happened. Such wells will not be placed near populated areas.

Even a massive geological event is unlikely to release large amounts of CO2 that is properly stored. First of all, CO2 will not be stored in areas where great earthquakes or other geological events are likely to occur. Second of all, earthquakes happen all the time in areas where water, oil or gas is stored in the ground the same way CO2 will be stored, and still there are no known occurrences of massive eruption of water or petroleum from the ground during such events. The trapping mechanisms are too strong for more than small fractions of the CO2 to be released even under such dramatic circumstances.

To ensure the safety of CCS, it is important that we get international regulations on how CO2 should be handled and stored early on. There are good and bad ways of storing CO2, just as with everything else. Poor choices in storage sites may increase the risk of rapid leaks, and must be avoided.

How do we know that it won't leak?

Correctly chosen storage sites have already proven themselves capable of holding water, oil or gas for millions of years. CO2 is stored either in depleted oil or gas reservoirs, or in deep water-filled formations. There are many trapping mechanisms involved that will keep the CO2 in the storage formation. The combination of these mechanisms are so strong that it would be highly unlikely that there would be any leakage.

Storage sites will be very closely monitored, and any leakage - should it occur - would be discovered and stopped quickly.

Read more about trapping mechanisms here

But what if there is a leak?

First of all, leakage from a CO2 storage site will mean that the CO2 enters the atmosphere and increases levels of greenhouse gases in the atmosphere. Of course, we don't want this to happen. But it is important to be aware of the fact that if the CO2 hadn't been captured in the first place, it would have gone directly into the atmosphere. Even in the case that some of the captured CO2 should leak, inaction - not doing anything - is even worse for the climate.

That being said, even if a leakage occurs, only a fraction of the CO2 would actually ever reach the atmosphere. Even in the case of a leakage, and even if the leakage isn't stopped, much of the CO2 would still be trapped in the storage reservoir. Any leakage would also be very slow. It would take considerable time for the CO2 to reach the surface, and all the stored CO2 would under no circumstance suddenly erupt to the surface.

Leakages would be detected early on. Storage sites will be closely monitored, and even minute leaks will be detectable. Leakages can be stopped using well known methods from oil and gas well repair. Should worst come to worst and it turns out that the storage site is too leaky to be used, the CO2 can simply be produced back (just as you would produce natural gas from a gas field) and moved to a better location.

Can CO2 storage sites explode?

No. CO2 is not an explosive gas. Although the pressure of the CO2 in the storage formation is high, it is no higher than the natural pressure at that depth. Any other gas or liquid at that depth, such as water or natural gas, is equally pressurized.

But what about blow-outs?

Blow-outs can occur in CO2 injection wells just as they sometimes occur in oil and gas wells. A blow-out is not an explosion, though. What happens is that for some reason the well fails, and some of the CO2 comes up at high pressure. This can be dramatic at the site of the well, but a century of experience from handling blow-outs in the oil industry has given us very good methods to stop blow-outs and repair wells.

Very little CO2 would actually be released in a blow-out, and it would very quickly be diluted into the atmosphere, not causing any immediate harm outside of the very close vicinity of the well. Of course it is important that anyone who works at the injection site is prepared and have the means to avoid injury to themselves should a blow-out happen.

Can CCS remove all CO2?

No. No solution can remove all CO2 alone. But CCS can, with the current technology, remove up to 90 percent of the CO2 from the emissions where it is used. If CCS was employed on the 2000 biggest emission sources in the world, 40 percent of all global CO2 emissions would be captured. That would make a very great difference.

It is also important to be aware that CCS is not meant to be a permanent solution in most cases. Eventually, we must stop using fossil fuels entirely. In time, industrial processes that emit CO2 may also be replaced by emission free processes, making CCS completely obsolete. But that is going to take a long while, and in the meantime we will need CCS as one of several measures to stop global warming.

What does it cost?

There are too many factors involved to give a simple answer to that question. The cost depends on the type of emission, the capture technology used, the distance to the storage site, the qualities of the storage site, whether the emission source is built with capture from day one or capture is retrofitted to an existing emission source, and variable costs like prices on materials and availability of real estate.

Since few full scale capture plants have been built yet, building costs are still quite high. These will drop as the technology becomes more widespread. Building common infrastructures for storage that can be used by many different emission sources reduces costs of storage. Improvements in technology increases efficiency and reduces costs.

However, as the capture and storage process requires some energy, this will increase the operating expenses of the emission sources. A power plant will use 10-40 percent of its energy output to run the capture and storage process, depending on the type of power plant and the technology chosen. Generally, the overall generating efficiency that is lost this way will be higher when capture is retrofitted to old plants, and lower when new plants are built with capture from day one.

Today CCS is dependent on some level of government subsidy or other support to be economically possible. However, in the future the cost of emitting CO2 will likely be much higher. This will make emission sources with CCS profitable. It is important to use national, regional and global policy measures to increase the cost of CO2 high enough for CCS to be widely employed on a global scale.

Will energy prices rise?

Energy prices will probably not increase as a direct result of CCS. However, a higher cost for emitting CO2 will increase energy prices. This will happen either CCS is employed or not. Producing energy from fossil fuels is very cheap compared to almost all other energy sources. To stop global warming it is necessary to make it expensive to emit greenhouse gases, and that means that fossil energy will become more expensive too, with or without CCS.

Is there enough room to store it all?

We don't know for sure how much CO2 can be stored. More surveys of potential storage sites is necessary, particularly in the developing and newly industrialized world, where less information is currently available. However, calculations predict that it is likely that at least 2000 billion tons of CO2 can be safely stored underground. Current global emissions of CO2 from power plants and industrial sources is about 11 billion tons pr year.

Isn't it better to just stop using fossil fuels?

Yes, that would be the best solution. But we are so dependent on fossil fuels it would be impossible to replace them all before late in this century. Projections by among others the International Energy Agency (IEA) predict that even if strong national and global policy measures to increase renewable energy are implemented, more than half our energy will still come from fossil sources in 2050.

The yearly consumption of fossil fuels today is equivalent of the output from 50 million wind turbines. Obviously, building that much renewable energy will take a long time. Even if great advancements are made in renewable energy technologies, building the actual turbines, solar plants, hydro plants or other renewable alternatives will require a long time, and in the meantime we are dependent on fossil fuels. CCS is the only solution to cut emissions from these fuels.

Isn't CCS just leaving our problems for future generations to look after?

No, in fact it's rather the other way around. CCS means capturing and storing emissions that would otherwise have been emitted into the atmosphere and would have contributed to global warming. Once CO2 has entered the atmosphere, it is likely to stay there for a very, very long time. The CO2 we emit today will make the world a worse place for future generations to live in.

By reducing emissions as much as possible, we are taking better care of the planet for the generations to come. As long as the alternative is emitting more greenhouse gases into the atmosphere, CCS is a way to stop the world from becoming a worse place in the future.

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