For the first time I heard on the news this morning mention of "a shortage of crude oil". This was in a soundbite about how UK petrol (gasoline) prices may well hit one pound (about 2 US dollars) a litre. By US standards that probably sounds pretty expensive, at about 7 or 8 dollars a gallon! We hear much about climate change and the need to curb our CO2 emissions, but the nub of the matter is probably the limited amount of oil there is in the ground, and how securely that might be supplied in the future. If indeed, crude oil supplies are set to fall shortly - they will at some stage in any case - we can manufacture synthetic oil from coal, using the Fischer Tropsch process, where the coal is first converted into a gas ( a mixture of carbon monoxide and hydrogen CO + H2) and this passed over a heated metal (iron or nickel) catalyst, which turns it into a mixture of hydrocarbons.
It was indeed this technology that kept Hitler's armies operating throughout World war II, to the consternation of the Allied forces who believed that Germany would run out of fuel within months, once their navies had cut-off supplies of oil from the US and the Middle East. By example, coal might come to our aid in the peaceful context of augmenting dwindling supplies of crude oil as we slide down the declining side of Hubbert's Peak following the advent of Peak Oil. However, some researchers have concluded that "Peak Coal" will hit the world by the year 2025.
Clearly if we begin using coal on the large scale to make oil, we will run out of the resource sooner than otherwise; coincidentally, "Peak Gas" is thought to arrive around 2025 (give or take half a decade), and hence if the Peak Coal prediction proves true (and much of the crude oil long gone by then), we will be in quite a pickle, unless we manage to abate our inexorable thirst for energy!
I was my understanding that world reserves of hard (anthracitic) coal amounted to 10 trillion tonnes, although I have seen some downwardly revised estimates of four trillion tonnes or so. The reality is that accurate data for coal reserves are scant and poor, and so a precise final figure is somewhat nebulous. However, it appears that the reserves and resources of coal have been overestimated on the global scale, and both quantities have been downsized during the past two decades from their previous values. According to the logic of classifying reserves (which are defined as being proven and recoverable) and resources (which is an umbrella term for all proven, inferred, assumed and even speculative amounts), over time advances in production and exploration methods allow some of the resources to be reclassified into reserves. 85% of coal reserves are concentrated in six countries, which are, in order of decreasing quantity of their reserves: US, Russia, India, China, Australia and South Africa.
The US holds a massive 30% of the world reserves and is the second largest global producer. China, albeit with far less coal than the US is way ahead as the world's number one producer, since it pays around 80% of its colossal and burgeoning energy bill from coal. Indeed, just 15% of Chinese coal is exported while the remaining 85% is burned at home. However, the US have passed their peak in producing high quality (anthracitic, i.e. 90% carbon) coal which hit in 1990. This potential shortfall has more than been compensated in terms of volume by production of sub-bituminous coal from Wyoming, and according to the stated reserves there, this can be maintained for another 10 - 15 years. It should be noted that sub-bituminous coal has a lower energy yield than hard coal, and so in terms of energy, US coal production in fact peaked 5 years ago.
It is thought that coal production may yet increase over the next 10 to 15 years by around 30%, mainly from Australia, China, South Africa and the former Soviet Union countries, in particular, Russia, Ukraine and Kazakhstan. World coal production will then reach a plateau (of unknown duration) and then eventually decline. The best estimate for world "Peak Coal" is around 2025, assuming production rates of 30% above current. Potential reductions in coal use for reasons of trying to avert climate change caused by anthropogenic CO2 emissions and global warming might push the peak further into the future - but probably not much further (10 years maximum, say?). It is the actual quantities of coal that will prove available for extraction that are the key issue, however, as indeed is true of all reserves of fossil fuels - including oil and gas.
"Coal Reserves and Future Production" (PDF) - link available in above article.