Carbon Capture & Storage

The jury is still out on whether Carbon Capture & Storage (or Clean Coal) will be a player in the world’s quest for a low carbon future.

This is due to Carbon Capture & Storage (CCS) being seen as being expensive at best, & at worst not working at all.

Coal is unlikely to go away as an energy source as it is cheap, abundant and often local. 30% of global greenhouse gas (GHG) emissions comes from coal. The USA gets 50% of its power from coal. China gets 80% of its power from coal & it’s building a new coal fire power station every week. In the last year China has become a larger emitter of GHG than the USA, however the USA emits 3 times per capita more than China.

Carbon Capture & Storage (CCS) involves capturing the carbon dioxide (CO2) & burying that CO2 deep underground.

There are 2 Problems with CCS; 1) no one knows if it will work (will the CO2 stay buried?) & 2) whether it works or not it’s expensive – so much so that alternative sources of energy look attractive. One serious attempt to investigate its use in a power station was the “Future Gen Project” in Illinois. It was cancelled when its expected cost went from $830 million to $1.8 billion

The capturing of the CO2 is not hard. CO2 reacts with chemicals called ‘amines’ – at a low temperature CO2 & amines combine, and at a high temperature they separate.

Power station exhaust can be purged of CO2 by running it through an anime bath. Then the anime is warmed to release the CO2 where it is projected to not do any damage.

It is a better method though to react the coal with water to produce a mixture of CO2 and hydrogen in which the carbon dioxide is much more concentrated than in normal flue gas which makes it easier to scrub out. What is then burned is pure hydrogen. This processing is expensive but it should work.

The disposal of CO2 is a major concern with CCS as it needs to stay permanently stored. In order for this to happen a lot of conditions must be met.

Successful burial sites have to be found & a lot of them. The body of rock to take the CO2 needs to be more than 1km underground. This depth gives the required pressure to turn the CO2 into a ‘supercritical fluid’ which makes it more likely to stay put. The rock must have enough pores & cracks to accommodate the CO2. Lastly, it needs to be covered with a layer of non-porous, non-cracked rock to provide a leak proof cap.

There are now only 3 successful CCS projects underway; 1) Nth Dakota – burying CO2 from coal gasification plant in depleted oil field. 2) Algeria, BP, strips CO2 from local natural gas – injects back into ground. & 3) Similar trick as 2^nd example at 2 places in the Nth Sea. None of these projects are linked to generating electricity though.

The scale of the problem is awesome. These 3 projects dump approx 1 million tonnes of CO2 / year. The American electricity industry alone generates 1.5 billion tonnes of CO2 / year. This would mean finding 1500 appropriate sites, & nobody knows if the country’s geology can oblige. Even transporting that amount of gas is a huge task.

A report in 2007 by the Massachusetts Institute of Technology (MIT) found that it would cost $25/tonne to capture the CO2 & pressure it into superfluid; & then $5/tonne to transport it to burial site.

Most optimistic proponents of carbon capture & storage (CCS) doubt it will be a serious alternative until 2020. An IPCC report says it will not be commercially viable before 2030.

There is presently not one full-scale demonstration CCS plant. If we don’t have 1 demonstration plant yet then how long will it take to build hundreds or thousands of them.

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