The article speculating on the use of coal as a substitute chemical feed stock ('Rich seams for chemicals', 23 January) was correct in pointing out that at present the world has reserves of oil equivalent to 40 (actually 44) years worth of production.
What the authors neglected to mention - and this is a sad fact for Australia as the world's largest exporter of coal - is that in 1965 the estimate was 35 years. The extra nine years added since are largely the result of the puzzling fact that the annual growth in proven reserves, worldwide, almost always exceeds production.
Further, should the figure ever start declining, the resulting price increase should make it worthwhile for oil producers to extract more oil from old fields (only a fraction of the oil in each field is extracted at present) and look at other expensive substitutes such as shale oil - ...
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