Q&A

We get a lot of questions on what CCS is and how it works. The most frequently asked questions are answered at the FAQ site. Most of the other questions are answered below.

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 can be stored in the pores. The CO₂ might try to move upwards to the surface, and there must be a solid rock on top of the porous layer to prevent the CO₂ from moving upwards.

This way of storing CO₂ is the same mechanism that has stored oil and natural gas below the ground for millions of years. The fact that oil and natural gas have been trapped underground for millions of years is a very good indication that CO₂ will remain safely stored.

There can never be a guarantee that CO₂ will not leak, but it is possible to store CO₂ at locations where the risk of leakage is very low. In the unlikely case of leakage we must be able to detect the leak and initiate remediation actions to stop the leak.

According to experts the risk of leakage is very low. If 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 after hundreds or thousands of years start to react with other minerals and form limestone (a solid rock), which is the safest form of CO₂ storage. That means that as time goes by the CO₂ storage will become even safer.

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.

Leakages can also be stopped if the injection of CO₂ is stopped and the pressure is reduced. That could mean that some of the injected CO₂ must be taken out of the storage site and injected elsewhere.

In general, 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.

Remember that oil and natural gas do not necessarily leak out of their reservoirs if there is an earthquake.

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.

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.

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 altered.

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

If a coal power plant is equipped with CCS it would increase the electricity cost with 2 to 3 eurocents per kWh electricity produced.

CCS is a new technology that so far only has been demonstrated in laboratories and small pilot plants. That means that there is still a long way to go before CCS technology is available 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. The first big CCS plants will probably need a lot of adjustments and re-designing before the work as planned. That is why they are called 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.

There will probably be a handful of CCS demonstration plants in operation by 2015. Some demonstration plants might even be in operation a year or two earlier.

There are many planned CCS Demonstration plants, and it is difficult to predict which of them that will be commissioned first. The most ambitious plan at the moment is the Kårstø CCS project in Norway that could be in operation by 2012, but no investment decision has been made, and it remains to be seen if it is possible to keep such an ambitious plan on track.

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.

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.

Operating a CO₂ capture plant will require large amounts of energy. If a coal power plant is equipped with a CO₂ capture plant, a large share of the energy produced by the power plant has to be used 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 loss, and advances are reported continuously. It is predicted that the capture, transport and storage of CO₂ will require 10 percent of the energy production of a coal power plant when the first CCS demonstration plants are set in operation around 2015.

The exhaust gas from a traditional coal power plant will contain approximately 10 percent CO₂. The remaining 90 percent is mainly nitrogen and water vapor. The CO₂ must be separated from the other components before it is injected. It is not possible to drop the capture part and transport and store all 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.

• Frequently asked questions