Monday, August 14, 2017

Carbon capture and storage


One keeps on encountering coal enthusiasts who believe that coal power stations can be made green by carbon capture and storage (CCS).  Well, of course, technically, they can.  But it would be very costly.

This article (Carbon Capture Is Expensive Because Physics) gives an excellent synopsis of the processes involved.  First you have to capture the CO2 from the flues of power stations.  Then you have to compress or liquefy the CO2 and transport it away for storage.  Then it has to be stored.  Each of these steps is expensive.  In fact, CCS would add (in the US) $168 to $196 per MWh to the cost of electricity generated by coal.  Lazard calculates the cost of new coal in the USA at $60 to $143 per MWh.  So adding CCS to a coal-fired power station would at least double the cost of electricity from coal.  And there is no guarantee that the CO2, once pumped deep underground, stays there.

OK, so what about this?

On the roof of a waste incinerator outside Zurich, the Swiss firm Climeworks has built the world’s first commercial plant to suck CO2 directly from the air. 
Climeworks says that its direct air capture (DAC) process – a form of negative emissions often considered too expensive to be taken seriously – costs $600 per tonne of CO2 today. This is partly covered by selling the CO2 to a nearby fruit and vegetable grower for use in its greenhouse. 
Climeworks hopes to get this down to $100/tCO2 by 2025 or 2030. It aims to be capturing 1% of global CO2 emissions each year by 2025.

[Read more here.  I mentioned another company which also hopes to extract CO2 from the air here]

Remember that right now, global temps are rising by a little under 0.2 degrees C per decade.  If there is no acceleration in this rate, the world will be 1.6 degrees warmer by 2100, and global temperatures will have risen by a cumulative 2.8 degrees since pre-industrial times.  This would be disastrous for our civilisation.  Catastrophic.  In order to limit the rise in global temperatures to 2 degrees C by 2100,  we will have to have negative emissions, i.e., we will have to remove CO2 from the atmosphere.   If we could site direct air plants near basaltic rock formations we could convert CO2 to rock, which at least eliminates the leakage problem.  It's technically feasible.

The trouble is that this seems very pie-in-the-sky, without a high carbon tax to make it economically worthwhile.  The costs of CCS give you some idea of what rate a carbon tax should be set at:  at least $120 per tonne of CO2.  And you can imagine the politics of that: the denialists and coal and oil interests would have a field day.  They object strongly to even $20 per tonne.

Far better never to emit the CO2 in the first place.  But it is probably already too late for that.

At my most pessimistic, I wonder whether mankind is wise enough collectively to take the steps necessary to stop emitting CO2 and then to start withdrawing it from the atmosphere.  It sometimes seems to me that we are, as a species, astonishingly stupid.

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