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CCS is a concept that continues to raise many questions. The most frequently asked are answered below. 

What is CCS?

CCS is short for CO2 Capture and Storage.

CCS is a technological concept to reduce CO2 emissions. The technology is applicable to large factories and fossil fuel power plants with large CO2 emissions. With CCS the CO2 is removed from the flue gas coming out of the factories and power plants. The CO2 is then injected deep below the ground, instead of emitting it into the atmosphere, as is the case today. Read more.

How does CCS work

CCS is a set of technologies that covers three main functions:

  • First, the CO2 is removed, or separated, from the flue gas coming out of factories and coal and gas power plants. This is called CO2 capture.
  • The CO2 is then transported to a suitable storage site. The transport is carried out in pipelines. Ship transport is also an option for offshore CO2 transport.
  • The CO2 is the injected into a suitable storage site deep below the ground. The storage site must be a geological formation that ensures safe storage without leaks.

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Is CO2 storage safe?

CO2 is safe provided that careful selection and characterization of storage sites are performed.

In order to store CO2 safely without leakage, the storage site must have a geology that stops the CO2 from leaking back up to the surface. In general, that means a geology with open pores where the CO2 can be stored and a solid rock on top of that to stop CO2 from moving upwards.

But a small crack in that geology can result in CO2 leaking up to the surface. It is therefore absolutely necessary to characterize potential storage sites before CO2 injection begins to ensure that there are no cracks that can lead to CO2 leaks. Read more.

Why do we need CCS?

Global warming is one of the most serious challenges facing mankind today. It is important to implement strategies to reduce the greenhouse gas emissions that are causing global warming.

The most obvious solutions are replacing fossil energy sources like coal, oil and natural gas with renewable energy sources and improved energy efficiency, which is using less energy and using it more efficiently. But these solutions cannot reduce greenhouse gas emissions sufficiently.

Experts says that the greenhouse gas emissions must be reduced by 50 to 85 percent by 2050. In order to achieve such ambitious emission reductions, it is not enough to rely solely on renewable energy and energy efficiency. Additional solutions are required, and CCS is one of the solutions because it has the potential to cut global CO2 emissions considerably by 2050. Read more.

How can we be sure that CO2 does not leak?

First of all, the CO2 must only be injected into storage sites that have been well characterized and classified as safe prior to the injection of CO2.

A safe storage site means that the CO2 will be injected into a layer deep underground with porous rocks where CO2 will be stored in the pores. The CO2 might try to move upwards, but there will be one or more layers of solid rock on top of the porous layer that prevents the CO2 from moving upwards towards the surface.

This way of storing CO2 is the same mechanism that has stored oil and gas below the ground for millions of years, including naturally occurring reservoirs of CO2. The fact that oil and gas have been trapped underground for millions of years is a very good indication that CO2 will remain safely stored in a similar manner.

There can never be an absolute guarantee that CO2 will not leak, but  CO2 will be stored at locations where the risk of leakage is very low. To be prepared for the unlikely case of a leakage, monitoring instruments and routines will be required, such that remediation actions to stop the leak can be performed.

Research shows that the risk of leakage is very low. When proper characterization of the storage location is performed prior to CO2 injection, the probability of leakage is that less than 1 percent CO2 can leak within 1000 years.

The injected CO2 will react with other minerals and form limestone (a solid rock), which is the safest form of CO2 storage. This will typically take several hundreds of years. That means that on the long term the CO2 storage issue is eliminated entirely.

What can be done if CO2 leaks?

If CO2 should leak there are ways to stop the leak. The highest risk for leakage is that CO2 will come out again through cracks in the injection well. If that happens the well must be closed down and sealed with cement, which is a long established practice from the oil and gas business.

Leakages can also be stopped by halting the injection of CO2 and reducing the pressure by relieving it. That could mean that some of the injected CO2 must be taken out of the storage site and injected in an alternative well.

Can earthquakes result in CO2 leakage?

CO2 will not be stored in areas where earthquakes are likely to occur. But even if an earthquake should occur at a CO2 storage site, research projects have shown that the CO2 will most likely not leak. Similarly, oil and natural gas do not usually leak out of their reservoirs if there is an earthquake.

What are the consequences if CO2 leaks?

If a leak should occur it will most likely be a small seep of CO2 leaking out at a low rate. That will not have any effect on human life. There are many natural seeps of CO2 several places around the world, and they do not harm us at all. However, the local ecosystems close to the leak could be affected, such as if pits water get contaminated, or if CO2 gas gathers in low lying parts or depressions in the ground.

If a burst out of large volumes of CO2 should occur, which is nearly impossible, the CO2 could displace the oxygen that we need to breathe, and that would be lethal.

The consequence of a CO2 leak is first of all a new source of CO2 emissions to the atmosphere that will contribute to global warming, and as such must be ensured not to take place.

Only in very unlikely situations, where CO2 is allowed to displace the air needed for breathing can a dangerous situation occur.

Can CO2 explode and burn?

No that is physically impossible. CO2 is not explosive, and it cannot burn, not under any circumstances.

How expensive is CCS?

If a coal power plant is equipped with CCS it would increase the electricity cost with 2 to 3 eurocents per kWh electricity produced. As the CCS technology becomes more widespread, this additional cost will be further brought down.

In the European context, with the EU climate policy becoming ever more stringent, within a few decades the CCS technology will be cheaper than paying for emission allowances. You can check how the price of CO2 emission allowances makes CCS cheaper in Poland here.

What is a CCS demonstration plant?

CCS is a new technology that so far has been demonstrated in laboratories and pilot plants. That means that there is still some way to go before CCS technology is mature and cost efficient for large-scale factories and coal power plants.

Scientists and industry agree that the next logical step to gain more knowledge and experience is to build large scale CO2 capture plants with CO2 transport and storage.

Why must we build CCS demonstration plants?

New technology will in most cases be developed in three phases: The first phase is research to ensure the fundamental principles work as theory says they should. The second phase is further development to improve the technology. This is often performed in small prototypes or pilots. When the pilot works as planned, the next phase is to build a demonstration plant in full scale. The experience and knowledge gained from operating the demonstration plant will form the basis for the final adjustments and improvements of the technology. If the technology now works as one originally hoped, the technology is ready for the market.

Like other new technologies, CCS also develops as described above. Scientists and industry says that research has taught us a lot about CCS, and they agree that the next step is now to build large-scale CCS demonstration plants.

When will full scale plants be in operation?

There will probably be several of CCS demonstration plants in operation by 2015. 

There are many planned CCS Demonstration plants, and it is difficult to predict which of them that will be commissioned first.

Where can CCS be used?

CCS is applicable for all stationary CO2 emission sources. That includes coal and gas power plants, refineries, and factories for production of steel, aluminium, cement, and ammonia.

How large emission reductions are possible?

There are different technologies for CO2 capture, and they have different potentials for CO2 capture. With the oxyfuel technology up to 100 percent of the CO2 emissions from a coal power plant can be captured and stored. Another way of capturing CO2 is post-combustion CO2 capture, which will remove 85 to 90 percent of the CO2 produced by the power plant.

There are more than 8000 factories and power plants worldwide where CCS is applicable. These factories and power plants emit about half of the global man-made CO2 emissions. If CCS is implemented to all these factories and power plants up to 50 percent of global CO2 emissions could be eliminated.

Why will CCS reduce the effiency of a power plant?

Operating a CO2 capture plant will require large amounts of energy. If a coal power plant is equipped with a CO2 capture plant, a significant share of the energy produced by the power plant is needed to operate the CO2 capture plant.

Transporting CO2 and injecting CO2 will also require energy, but that is minor compared to the energy required by the capture plant.

Research is ongoing worldwide to reduce this energy penalty, and advances are reported continuously. It is predicted that the capture, transport and storage of CO2 will require in the order of 10 percent of the energy production of a coal power plant when the first CCS demonstration plants are set in operation around 2015.

Why must CO2 be captured

The exhaust gas from a conventional coal power plant will contain approximately 10 percent CO2. The remaining 90 percent is mainly nitrogen and water vapour. The CO2 must be separated from the other components before it is injected. It is not feasible to aviod the capture part and instead transport and store all of the flue gas. That would have increased the transport and storage cost by a factor of ten. The transport pipelines would have been impractically large. The storage sites would have been filled up ten times as fast, and that would have critically limited the global CO2 storage capacity. In addition, the storage sites would have been contaminated with additional components other than CO2, components whose injection underground is prohibited.

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