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Tag Archives: carbon capture and storage

Commercial viability of CO2 capture and storage – of course not (under the historical paradigm)

A recent article titled “Government impose ‘carbon capture levy’ to fund coal-fired power plants”, discusses the UK government imposing a tax on electricity to potentially fund carbon capture and storage (CCS) development on up to four coal plants over the course of 10–15 years. A quote from the article sums up the discussion:

“The Department for Energy and Climate Change said yesterday that uncertainty over the commercial viability of CCS meant that public support might have to continue beyond 2030.”

Of course CCS is not commercially viable. The only way to make it commercially viable is to internalize the cost of CO2 emissions to such a degree that the cost of investing in the infrastructure for capturing the CO2 justifies the investment. The price of CO2 is not there yet for the UK, and is nonexistent within the United States. So the commerical viability question is not even applicable except for potentially using captured CO2 to extract more oil out of mature reservoirs. Still, given that there are natural sources of CO2 that only require major investments in pipelines while avoiding interacting with the electricity indudstry, a sufficient CO2 price may not exist for a couple of decades that induces investment in CO2 capture on coal plants.

But the real “commercial viability” conundrum rests on the fact that a large portion of society believes that we (well, the industrialized world) should place a value on reducing CO2 emissions. Capturing CO2 from coal plants will lower their net electricity output by 20–35%. In terms of the normal venacular of economics, this is going to something less efficient. In this case, the efficiency is less electricity output per unit of fuel input. This is a fundamentally different concept than has occured since the dawn of the industrial revolution.

Sure, we have imposed certain types of pollution mitigation technologies on power plants before (e.g. SO2 and NOx scrubbing, mercury capture), but these have for the most part not prevented coal plants, and the power plant industry in general, to increase their efficiency over time by increasing the pressure and temperature of operation. But everyone knows that the thermodynamics of the power plant with CO2 capture will be less efficient. This goes directly against the purpose of investments and technological advancement since the founding of modern civiliazations.

People have historically invested in ways to extract more productivity and wealth from the Earth per unit of effort (human effort) until some ecological feedback prevents that from being a desireable option any longer. These feedbacks to date have mostly been associated with direct air-, soil- and water-quality problems. And the past mitigation methods have been of a small order of cost such that the human population has continued to grow since the Industrial Revolution. But this feedback fo global warming appears to cost several orders of magnitude more to deal with. The question is: “Is coal power so valuable to us that we will continue to use it even at lower efficiency?” In other words: “Are other viable technologies so inferior that coal power must continue to exist by providing less direct services than it has since we first put it in a steam cycle connected to a dynamo?”

So far, the answer seems “yes” to these two questions. Widespread use of CCS will mean that we value environmental/ecosystem services more than energy services on a larger scale than any time before in history of human civilization.


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Coal clean-up goes underground

A team in Germany has calculated that underground coal gasification combined with an above ground electricity plant and storage of the resulting carbon dioxide back underground can both cut carbon emissions and compete with other energy technologies in the European market. Thomas Kempka and colleagues at the research centres of GFZ Potsdam and RWTH Aachen see the technology as a bridging measure until use of renewable technologies becomes more widespread.

The technique works by drilling two wells into a deep coal seam. The first, an injection well, introduces oxygen and water vapour into the seam, encouraging gasification of the coal at high pressure to produce hydrogen, methane, carbon monoxide and carbon dioxide, which leaves the seam via the production well. The methane and hydrogen can be used as fuel directly, or to create methanol, and also to run a combined cycle electricity plant. Carbon dioxide removed at the surface can then be pumped back down and stored in coal seams where gasification has been completed.

The team reckons the maximum amount of carbon capture achievable in this way is 86%. This would create an energy generation technique 20% cheaper than nuclear electricity generation but with similar emissions. But even a 50% capture rate would bring coal emissions down to those of natural gas.

There has already been considerable research into carbon storage in empty coal seams and into coal gasification, which gives the researchers a head-start, although they reckon it will be 15-20 years before large-scale use of the process. The team has calculated that Europe would have enough coal for this Underground Coal Gasification-Carbon Capture and Storage technique to fulfil all its energy needs for 68 years, although they believe that is important to maintain a mix of sources.

Kempka and colleagues are currently using a 25 square km sample area in Germany that contains 7 coal seams for theoretical studies. They have calculated that to run a 600 MW power plant requires nine square kilometres of coal seam with an average thickness of 1.5 m. This would give a runtime of 20 years, with each seam being used up after about three years and becoming available for carbon dioxide storage. Storage during the first three years, meanwhile, could take place in saline aquifers.

Several aspects of the technique require further investigation, said Kempka at the EGU meeting, including environmental issues such as subsidence, aquifer pollution from compounds released during the gasification process, the safety of the carbon storage, and whether carbon dioxide can dissolve pollutants and transport them elsewhere underground.

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