Monday, December 04, 2006

Coal May be Crowned King after all!

Further to my recent posting "Shall Coal be Crowned King?", Mcrab posted a couple of very much appreciated "comments", to the effect that there may be a lot more coal than I had been led to believe! The 220 million tonne figure for U.K. coal reserves on which I based my calculations for these islands, only represents the amount of coal that is currently in the holdings of the U.K. mining industry. Prompted by his suggestion that the UK may in fact be sitting on 190 billion tonnes of coal, I managed to dig-out the following text from a 1991 House of Parliament transcript, which does indeed place the subject of coal reserves under quite a different light:

"The (British Coal) Corporation's estimate of coal in place in the United Kingdom (that is in seams over 60 centimetres thick and less than 1,200 metres deep, minus coal which has already been worked) is 190 billion tonnes." It goes on to detail technically recoverable reserves. It is valuable, not least because it parallels much of the important information available in the Brown Book on the oil and gas sector...

I commend the order to the House.

Question put and agreed to.


That the draft Coal Industry (Restructuring Grants) Order 1991, which was laid before this House on 15th April, be approved."

So, let us reconsider the case for coal, and where it might be found. Coal occurs in the form of layers (‘seams') in sequences of sedimentary rocks. Almost all onshore coal resources in the UK occur in strata of the Carboniferous system, and coals of this age also extend into the North Sea basin. Individual seams may be up to 3.5 m in thickness although, exceptionally, thicker seams also occur. Resources of coalbed methane (CBM) that may be developed in the future are also contained exclusively in Carboniferous coals. In Northern Ireland lignite, or "brown coal", of Tertiary age is a significant resource, which could be used in power generation. In Great Britain coals of Mesozoic and Tertiary age are insignificant onshore but occur over large areas, and in considerable thicknesses, in the North Sea basin and other offshore areas.

It is thought that 45 billion tonnes of the UK's reserve can be extracted using current technology. We burn 62 million tonnes of coal each year in the UK, and produce only 20 million tonnes of that ourselves. Reckoning that three tonnes of coal can produce one tonne of synthetic oil by goal liquefaction, and we use around 72 million tonnes annually (57 million tonnes for transportation and the rest as a chemical feedstock for industry), which could, in principle anyway, be got from 72 x 3 = 216 tonnes of coal, our entire coal requirement comes out at 62 + 216 = 278 million tonnes. Hence, as a rough estimate, there is enough for 45,000 million/278 million = 162 years... and if we can get at the entire 190,000 tonnes, we are set for 190,000/278 = 683 years. The time allowed us by the first 45 billion tonnes ought to be sufficient to develop more sophisticated means with which to extract the rest of the 190 billion tonnes! I am just doing simple sums, in order to make the point that running out of coal is not the issue, we have plenty of it and the considerations to be addressed are rather how cleanly the resource is used, and the huge mining and processing infrastructure that will need to be introduced from scratch. In other words, we will need to dig a completely new network of mines. It is thought possible to extend the existing mines to garner around one billion tonnes of coal in total, and we are after much more than that.
It occurred to me that this new mining network would probably cover quite a large underground area. As usual I shall use rough numbers (since that is all there is, also as usual!). If coal seams must be at least 0.5 metres thick to be worth considering, and there are "nugget" seams up to 3.5 m thick, then an average thickness of 2 m overall, might be a reasonable estimate. Taking an average density for coal (it varies quite a bit in fact) of 1.4 grams/cubic centimetre (1.4 tonnes per cubic metre = 1.4 t/m*3), gives:

2 m x 1.4t/m*3 = 2.8 t/m*2, i.e. 2.8 tonnes under each square metre area. Hence 190 x 10*9 t/2.8 (t/m*2) = 67.9 x 10*9 m*2 which is about 68,000 square kilometers (km*2). By way of scale, this is (68,000/244,000) x 100 = 28% of the area of the UK mainland, not that the workings would be all under this visible island home, but an appreciable amount would be dug into the seams under the north sea. It is still a big area, nonetheless!

Most coal-fired electricity generating power stations are quoted at an efficiency of around 35%, or about a third of their thermal power (i.e. the heat that could be got from the coal assuming 100% efficiency). The factor of "a third" applies to nuclear power station too, and so Sizewell B at 1200 MW (that is electricity production), actually produces three times that in terms of thermal power (heat), and so is nearer 3,600 MW. This is important in calculating how much uranium is needed to fuel a nuclear power plant for a year, say... As Mcrab points out, there are integrated systems being evaluated with higher efficiencies than this, and the general consensus I can find for IGCC (Integrated Gasification Combined Cycle) plants, which gasify the coal and burn the gas from it as the fuel to drive the electric turbines, is a figure closer to 50% (up from "a third" to "a half"). This looks good, but the plant is much more sophisticated to design and construct, and hence more expensive.
A typical cost for building a coal-fired station is $1,500 per kw of generating capacity. Hence a typical 1 GW (1,000 MW) station is generating 1 million kw and would therefore cost one million x $1,500 = $1.5 billion to build. Figures for IGCC plants are really still on the drawing board, but I did find one set of costings that implied an initial investment of 20 times that; however, this would almost certainly fall as the technology became more widely adopted. Another advantage of the technology is that some of the gas could be extracted for conversion to oil by "liquefaction". Heat can also be drawn-off rather than wasted at various stages during the operating cycle and used for ancillary electricity generation.
Even environmentalists are warmer in their regard of IGCC's since they are more readily adapted to capture CO2 for its potential long-term sequestration. My own view is that "sequestering" (i.e. "locking up") CO2 in the wrong place, could be a legacy of global climate disaster to future generations, e.g. if for some reason - an earthquake say - the store of CO2 were to be suddenly released at a later date. That could really screw-up climate models, and their forecasts! Possibly such consequences of geoengineering could be factored in, on a betting odds basis. However, the energy costs of CO2 capture and disposal are close to those gained by the 35% to 50% increase in efficiency from opting for IGCC systems in the first place. However, if we are to go down this road, and arguably we have no choice, in order to prevent the "rate of increase" of CO2 levels from increasing, we will be running harder to maintain the same pace.
In my very first posting, back in December 2005, I discussed the need for a suite of energy sources, and I feel it is most likely that we will see more new coal powered stations, more nuclear power, and new technologies being implemented as time goes on. It is sobering to note that China opens the equivalent of 4 new typical UK power stations every week! - none of which are of a more efficient (IGCC or any other) design. If coal liquefaction will (and I have taken the extreme of providing 100% of our oil from coal in my reckoning) become increasingly important, it is likely that some very attractive integrated plants will be introduced (check Mcrab's figures in his comments to my "Shall Coal be Crowned King" posting), to provide both heat (electricity) and hydrocarbons, but mostly (cheaper!) tried and tested all-out coal liquefaction plants based on Fischer-Tropsch chemistry, as used extensively in South Africa by Statoil. It is always money that wins, and introducing new technologies which offer greater energy efficiency or renewables on the large scale will only happen if and when the economics of the "energy-game" so dictate!

In regard to how much coal the world has as a reserve, estimates vary, but Russia has 6 trillion and China 1 trillion tonnes, so a world reserve of 10 trillion tonnes is probably reasonable. However, only 1.2 trillion is accessible to current or readily adaptable mine workings, and so an enormous coal-scrabbling investment will be required to scratch it out of the ground, with all kinds of environmental issues attending. However, to put the quantity there in perspective, I note that the countries of the world used in 2004, 3,770 million tonnes of oil. To produce this equivalent (and crude oil and syn-oil are NOT chemically equivalent) synthetically from coal, we would need 3,770 million x 3 = 11,310 million tonnes of coal plus the 5,540 million tonnes currently used already, i.e. we would need to roughly treble our coal production to meet this total demand, on top of the fuel required to actually run the processes themselves. However, if we are on-target about how much coal there is, we have:

10 trillion = 10 x 10*12 tonnes/(11,310 + 5,540) x 10*6 = 593 years worth.

This is a similar value to the 683 years I worked out for the UK. There is a hell of a lot more to it than this though.... My point is that shortage of coal in the Earth per se is NOT at issue, it is getting at it, extracting it and the attendant environmental aspects (dangers!) of this and how it is finally used that are.

1 comment:

Coal said...

The use of sophisticated software systems for coal mining that is mostly burnt for power generation and steel production and adds to the greenhouse effect is valid for western countries who may allocate resources and funds to alternative and more greener sources of power. Some of the alternatives may be "safer" than the traditional mines. Unfortunately, coal market news show developing economies are more likely to increase their use of thermal coal & metallurgical coal in coming years because of its affordability and to meet increasing demands for electricity and steel. Whether they will embrace and utilise sophisticated software systems that no doubt add to the cost of production is yet to be seen. Cherry of