Wednesday, November 02, 2005

Carbon Capture and Storage: What's that about?

Carbon capture and storage, what is it and why are we interested?

When asked about carbon capture and storage in economic terms, when compared to say renewable energy sources the chair of the IPCC special report on the subject was to professional to smirk, he merely pointed out that "the report considers CCS as an option in the portfolio of mitigation actions for stabilisation of atmospheric greenhouse gas concentrations". Or to put it more bluntly CCS is essential to a low carbon economy, as are renewable energies, energy efficiency measures and overall lower primary energy consumption. We don't have a little problem here that we can simply opt in and out of, picking our favorite technologies. We currently emit about 6 billion tones of carbon with 6.5 billion people, by 2050 there will be around 9 billion people and we need to reduce emissions to 2.2 billion tones.

(for a explanation of this need and the reasoning behind this reduction target check out my earlier report here)

Carbon capture and storage is: "a process consisting of separation of co2 from industrial and energy-related sources, transport to a storage location, and long-term isolation from the atmosphere". The attraction of CCS is that the scale of emissions reductions could be enormous. If we capture all the carbon from powerplants around the world we would have removed a very major part of global carbon emissions. Another very important consideration of CCS is a practical and political one, there are vast reserves of Coal in the USA and in China. With other fossil fuels located around the world, but not in China and the USA security of supply is a major consideration. It has been suggested by many that weather we like it or not these supplies of cheap and secure energy will be used. This links strongly in to the political dimesnion, if CCS in encouraged, with federal assistance in the US and national action in china, then a battle against the powerful coal lobbies can be avoided and the issue of climate change can start to unite not divide society.

How developed is the technology, can we actually do this?

There are actually 3 kinds of CCS; geological, deep sea and carbonation. Of these types geological is by far the most mature in terms of technology. Much of the equipment used in the extraction of nmatural gas can be used in the transport and storage of carbon dioxide, capturing of carbon dioxide is the most novel part of the process. Even carbon capture from flue gas is already occurring, mainly at industrial sites rather than power generation sites, for example metal works and fertilizer factories are already present with this technology in place. The table below outlines the current state of technology.

One example of CO2 being pumped into the ground on a large scale is in Norway where: "Statoil has been re-injecting CO2 co-produced with natural gas into a deep aquifer overlaying its Sleipner field, solely for storage. Since 1996 around 1MtCO2 a-1 has been stored there."

Like the injection facilities the pipelines are also well developed: "the construction and operation of a CO2 pipeline for this distance [50km] is neither a technical nor a commercial challenge"

What are the practical obstacles?
The main potential obstacle to carbon capture and storage is the availability of storage, either in depleted reserves or in aquifers. Fortunately studies have shown that a large number of centers of population globally are within 300km of a suitable carbon store (see below). In terms of size it is estimated that around half of all our emissions over the next 45 years could be stored in depleted oil fields. Far more than this could potentially be stored in deep saline aquifers. It turns out the main obstacles apart from cost are likely to be regulatory, particularly if pipelines contain more than trace amounts of sulphur compounds in which case planning applications can be very difficult.

What are the safety considerations?

Carbon dioxide is non toxic, it is however heavier than air and tends to settle in depressions, this must be considered when siting pipelines. The overall risks are similar to those associated with gas pipelines because although having an extra risk associated with large scale leakage carbon dioxide is not flammable so there is no chance of explosions. Carbon dioxide is also non-corrosive, even when mixed with a variety of impurities, it is therefore safe to pipe without concern of corrosion. The proviso is that water must be removed from the CO2 stream before it is compressed as water with CO2 is corrosive. There are a large number of carbon dioxide pipelines throughout Texas at present, where they are used to transfer CO2 from one resevioir to another where it is used to force out natural gas.

How much will this cost?

For a typical new power plant it is expected that carbon capture and storage will cost around 25-30 $ per tone of CO2. The table below gives some further explanation. The EU emissions trading scheme is beginning to reach these levels but generally throughout the world carbon taxes are not yet applied, until this happens CCS will not take off and a technology that has great potential in the fight against climate change will be left on the sidelines for the sake of a few pence per KWh . For comparison, carbon dioxide reductions using biofuels usually cost >100$ tCO2, small scale renewable energies are similarly expensive, only certain energy efficiency measures come close to this tiny cost per tone of savings.

EOR is Enhanced oil recovery and lowers the cost of the project to next to nothing, there are several place around the world using CO2 for EOR but not as yet CO2 from power stations.

How will CCS effect broader emissions reductions?

The usual scenario for CCS is a power station producing electricity for households, using coal to do this and also locking away the carbon dioxide. Two important variations on this theme could have dramatic effects on global atmospheric carbondioxide emissions. Firstly, a hydrogen economy is increasingly seen as the future of the automotive industry, but where exactly all the hydrogen is going to come from is something of a moot point, it could come from electrolysis of water at coal power stations with CCS technology, this increases the emissions reductions achievable through CCS dramatically. Secondly, Bio-Energy Capture and Storage (BECS) is a technology that may be key to reducing global emissions significantly. BECS involves the use of biomass for fuel,the resultant carbon dioxide is then stored underground, because plants get there carbon from the atmosphere this is basically a way of removing carbon from the air and piping it underground, sounds like a good idea to me!


For more information on energy matters check out TheWatt, a weekly podcast, forum and website. The Alternative Energy Blog also covers similar issues.

The main reference for this article is the IPCC special report on carbon capture and storage.

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At 8:29 PM, Anonymous Anonymous said...

Has there been any work done on the storage and use of CO2 as a refrigerant for use in cooling for buildings or industry?

At 11:21 PM, Blogger vicini said...

A cooling system will have several hunderd pounds of coolant, not enough to worry about. The pressures in the refrigeration cycle would be 3 to 4 times that in a freon cycle.

At 9:01 AM, Anonymous Dane Pflueger said...

Thank you very much for this informative article. It would be amazing if actually these Carbon Capture Storage (CCS) establishments are a big success.

However the issue of finding the storage is serious. Check out this title from the Guardian “Not in our backyards, say Germans, in blow to C02 plans" few days back and I support them.

It certainly scares me to think that foundation of my house is made up of carbon. However, after reading your article I got to know that CO2 is not toxic in nature. A big relief however is that government needs to educate people about the Ps and Qs of CCS. We all want to live in a green world where we can breathe fresh air. Anyone though would get jittery to think of lighting the world at the expense of his/her own household.


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