Wednesday, 5 November 2014

Old King Coal was a gasification soul ....

As a result of the no vote the process of coal bed gasification is once more rearing its head in Scotland as a number of Caudrilla / Vitol spin off companies seek planning permission to use this process in seams under the Forth as part of a ‘commercial development trial’. 
Just how dangerous is the process of coal gasification, what is the evidence, either way, and how ‘new’ a process is it?

The technical problems are vast in an underground burn compared to testing the organic chemical reaction in a controlled pressure vessel at carefully regulated oxygen levels, pressures and temperatures. The main concerns as I see them are:

  1. How are they going to capture the sulphur and other bye products from the burn because Forth Basin Coal has a fairly high sulphur content. 
  2. There is the complex geological nature of most pits in the basin with micro faulting breaking up the seams - how will the burn though impact on that?
  3.  How do they control the reaction along the seams where the coal varies in significant quality and water content?
  4.  What will be the thermal impact of the 900C burn and reaction on the surrounding rocks in terms of micro fracture and slippage as the burn leaves them unsupported?
  5. What is the potential impact on the local water table?

According to current best practice, coal gasification should be carried out:

  •  At least 300 feet under  and up to 1,400 feet under sea level
  •  In a seam thickness of more than 5 metres
  •  With an ash content of less than 60%
  •  In seams with minimal faulting
  •  Isolated from liquid aquifers (that is coal beds capped by impermeable bed rocks such as clay or granite)

So the reality is there are not a huge number of coal seams in the Forth basin which will meet these criteria, except under the Firth of Forth where it is known seams do run its full width with reduced faulting, so will best meet current best practice criteria for coal gasification - if planning permission to commence extraction is given. The problem lies in the weakness of the over lying rocks which make up a lot of the Firth’s sea bed geology, have caused collapses and allowed flooding into the preceding ‘sea’ pits along the Fife and East Lothian coasts. There is also the unresolved problem of burning seams which have been abandoned – such as at Seafield near Kirkcaldy and the impact of the gasification process generating 900C reaching the sizable pockets of methane created by the uncontrolled burns from these pre-existing coal seam fires. 900C is the optimum temperature burn to ensure maximum methane production in the combustion mix.

Coal gasification was proposed as far back as the 1880’s when limited attempts were made to try the idea out but the cost was far greater and less certain, than conventional means of creating coal gas. The next burst of interest in the UK arose in the run up to the First War in 1914 but the war terminated any further experiments for the duration. In the interwar years it was the Russians who lead the way with major commercial schemes but these also fell away as Soviet Russia exploited its own oil and gas reserves in the Balkans. In the mid fifties the burgeoning availability of cheap oil and gas from the Middle East saw an end to all proposed and active coal gasification schemes across Europe. So the idea is not ‘new’ it was just waiting until the economic climate was right, that time is when 1 cubic metre of natural gas (methane) exceed the cost of 1 cubic metre of methane from gasification (Syngas).

With oil at over $100 a barrel that economic switch point had been reached and a UK Government, with a imminent power shortage problem on its hands, is desperate for these so called ‘Syngas’ power plants to be generating power as fast as possible in order to escape the hole the UK Parliament’s failure to drive forward any sort of legitimate or cohesive future power policy, has dug for itself in the last three decades. Fracking is struggling to get a toe hold ‘on shore’ in the UK as the horror stories of the pollution of human water resources, the creation of water shortages in US states (where there had previously been none), the smell, the contamination and the sink holes (one sink hole is currently under-mining a key dam in the USA Tennessee Valley hydro, flood control and irrigation scheme), plus localised earthquakes all give rise to justifiable cause and concern of the suitability of ‘fracking’ in a land with such a high population density as England south of the line of Manchester and Leeds, part of the UK where water supply is already becoming an increasing problem.

Environmental claims for gasification are the reduced level of pollutants as Sulphur and Nitrous Oxide (as they are claimed never reach the surface) combined with seven times less the amount of airborne ash compared to current crushed coal technology. The problem is to maximise minimal pollution the oxygen levels and temperature of the burn has to be accurately controlled. This works well with surface gasification plants but the ability to control the temperature and rate of burn underground can only be estimated and leaves some doubt to claims for underground gasification’s environmental credibility.  At one test site the pressure within the burn cavity was too high and forced phenols and carcinogenic benzenes into the local water table. They did not return to ‘normal’ levels until two years after this test finished, according to research.

As for the claims of carbon reclamation and storage, the jury is out. The technology is still in its very early stages and the results are so far not as impressive as the continuing claims for carbon storage both the industry and environmentalists would like you to believe.

Without labelling the answers to my initial five questions, all seem to have been covered in some shape or form to this point. 

In terms of coal bed gasification under the Forth we can suggest that water table contamination from benzene or phenols is unlikely to happen. Instead of sink holes, it is more likely there will be seabed collapses. The output of the coal bed system cannot be as clean and environmentally friendly as its proponents claim simply because the ability to control the burn underground can never be as accurate as the surface experimental trials appear demonstrate. Throw in potential sea water ingress, the quality and water content of coal in the seam being at best an estimate and the scientific based environmental argument put forward by gasification proponents begins to lose its sheen.

The sole, apparent advantage for coal bed gasification is commercial price per unit but with Saudi Arabia currently flooding the world markets with cheap oil and gas, the question again becomes:

 Is gasification really the best solution to the UK Parliament’s failure to plan ahead for UK energy needs?

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1 comment:

  1. Sounds rather dodgy to me, especially when Scotland is well on the way to being self-sufficient in cleaner renewables. My biggest point against, is why do we have to squeeze every last drop of oil and minerals from the earth. Our kids and grandkids won't thank us
    Thanks again for highlighting this Peter