Monday, 12 September 2011

Is carbon capture and storage too expensive?

Carbon capture and storage (CCS) is potentially an important strategy for reducing the effects of climate change. The idea is that we can safely continue to burn fossil fuels as long as we either capture the carbon dioxide from the exhaust gases or retrieve it from the atmosphere, and store it safely. There are many ways of doing this, though few have been tested at an industrial scale, and it is often said to be too expensive. Is it really? I have done some simple analysis to see what the impact would be on the prices of things we buy from day to day.

Most CCS schemes capture CO2 from a concentrated source such as the flue from a power station. It is harder to capture CO2 from the atmosphere because the concentrations are lower and it will cost more. Some estimates put air stripping at $500/tonne[1] compared to $150/tonne [2] for flue gas capture (plus a bit for transport and storage). However, a lot of that cost is energy and it can be done more cheaply. For example, Global Thermostat is running a pilot plant in California which uses waste process heat (in this case from a solar concentrating power station) as the energy source for capturing CO2 from the air.

In the table below I have assumed the cost of CCS is £50/tonne for power stations and £100/tonne for the air. The first figure is a bit higher than given in [2] and within the range specified by [3]. All the carbon emissions are as given in my book unless otherwise stated and I got the prices from a quick web search - these will of course change over time.

What kg CO2/unit Cost of CCS £/unit Current £/unit Price increase
Electricity:1 kWh 0.545 £0.03 £0.12 23%
Gas: 1 kWh 0.185 £0.02 £0.04 46%
Diesel: 1 litre 2.672 £0.27 £1.39 19%
TV (smallish) 100 £10.00 £250.00 4%
Car: Toyota prius 5720 £572.00 £23,000.00 2%
Beef: 1 kg mince 18 £1.80 £3.00 60%
Bread: 800g loaf 0.8 £0.08 £1.25 6%
Beer: 1 pint 0.3 £0.03 £3.50 1%
Book: an average paperback 2.5 £0.25 £7.99 3%
House: 80m2 [4] 60000 £6,000.00 £200,000.00 3%

That's a huge hit for gas consumers, even bigger than the massive hikes we've seen recently. In 2008, British Gas customers saw a 35% rise [5] but that is still a record. The price of CCS for electricity  is relatively modest in comparison and this would go down in the future if we use more renewable sources. For manufactured goods the increases are no more than we normally expect from inflation, except for some foods. Meat generally, and beef and lamb in particular, have very high associated greenhouse gas emissions.

It seems to me therefore that though low income groups will need support for gas and food bills, the overall hit to the economy from CCS would be low. However, there are limits to how much CO2 we can in practice strip out of the atmosphere.

Firstly, there is the question of where we store it. Saline aquifers and depleted oil wells are generally favoured. The UK continental shelf and the North Sea can apparently handle 10 Gt which is 80 years of our coal power stations output but only about 15 years worth of our overall greenhouse gas emissions [6].

Secondly, the energy needed to capture the gases might be better used in other ways and there is a limit to the amount of waste process heat available.

Financial cost is not going to be the limiting factor for CCS, its the energy requirements and storage capacity.

[1] Climate Crunch: sucking it up (Nature April 2009)
[2] US Department of Energy: Carbon Capture Research
[3] Parliamentary Office of Science and Technology: Carbon Capture and Storage (march 2005)
[4]SUSTAINABLE HOMES: EMBODIED ENERGY IN RESIDENTIAL PROPERTY DEVELOPMENT A Guide for Registered Social Landlords says a house will have embodied carbon emissions of 500-1000 kgCO2/m2 of house space. I have assumed 750 kgCO2/m2.
[5] Record rise for British Gas Bills
[6] 2050 Pathways Analysys DECC


  1. I have to admit that I haven't taken the time to fully understand the argument you're making here.

    But one thing that strikes me: you've got a relatively large table of numbers up there, and arguments presented in such ways, in my 'umble opinion, are perceived as too complex for many (most?) people to bother taking the time to fully understand. People such as me, today, for instance.

    On a gut level, my feelings regarding carbon capture and storage (CCS) is that it is yet another techonological solution to a problem caused by technology. And in no discussion of CCS that I've ever seen -- not that I can really say I've studied the subject -- does anyone ever make the point that trees are a CCS system.

    We're currently losing, from our hard-pressed planet, some 1500 acres a day of carbon-sink forestland due to our raping of the Earth. With this in mind, CCS is simply a distraction: I think we should simply say stop forest destruction. NOW.

  2. Trees are a form of carbon capture. But it isn't permanent, it takes time, and it takes up a lot of land. See my earlier post.