Consider this: There is 13 times as much energy in coal in the form of Thorium as there is available by burning the coal, and right now we literally throw it away in the ash pile!

What is Thorium?  It's a fertile material.  That means that when struck by a neutron in a reactor it transmutes via a nuclear process to an element that is capable of fission.  Note that Thorium itself is not fissionable - that is, it will not (directly) split and release energy.  Instead it captures thermal neutrons and turns into Uranium-233.  U-233 is fissile.

There is a type of nuclear reactor that utilizes this fuel cycle.  Instead of the traditional nuclear reactor which uses water a moderator and coolant (either a boiling or pressurized water reactor) these reactors use a liquid salt.  In the vernacular they're called "LFTR"s, pronounced "Lifter." 

You've probably never heard of them.  But they're not pie in the sky dreams.  Our nation ran one for nearly four years in the 1960s at the Oak Ridge National Laboratory.  It was scrapped in favor of the traditional uranium fuel cycle we use today because the fuel it produces is very difficult to exploit for nuclear weapons, and it breeds fuel at a slow rate.  The natural process of the nuclear reactions in the core of such a unit produces a byproduct that is a very strong gamma emitter that is difficult to separate from the other reaction products.  For this reason - and because we wanted both nuclear power and nuclear weapons - we built the infrastructure for uranium and plutonium rather than thorium.

Thorium-based reactors have several significant advantages and a few disadvantages.  We have much less experience with LFTRs than traditional nuclear power, simply because we stopped working with them for political and war-fighting reasons.  They use a fluoride salt which is quite reactive when in contact with water, but the reactivity is a bonus in all other respects, because it tends to encapsulate the reaction products (the nasty fission products that you don't want in the environment) through that same chemical process.  It runs at a much higher temperature (typically 650C) than a traditional reactor and unlike a traditional reactor the fuel and the working fluid is the same - there are no fuel rods that can melt and release their nasty fission product elements, as the fuel is dispersed in the coolant.

Finally, the unit is intrinsically safe.  It does not require high pressure; the working fluid and coolant is a liquid at ordinary atmospheric pressure.  This gets rid of the need for high-pressure pumps, pipes and similar materials.  Without the moderator the reactivity is insufficient to sustain a chain reaction, and the moderator is in the reactor vessel itself through which the fuel/coolant is pumped, so criticality is impossible outside of the reactor vessel and inside the vessel the fuel and coolant are the same, and a liquid.  The working fluid is contained in the reactor loop by an actively-cooled plug.  If power is lost cooling ceases and the plug melts; the working fluid then drains into tanks by gravity under the reactor and cools into a solid, as it cannot maintain criticality outside of the reactor itself (there's no moderator in the tank or the plumbing.)  As the fuel is in the fluid, there is no core to melt as occurred in Japan and being dispersed over a much larger area the working fluid naturally cools from liquid to solid without forced pumping and cooling.  This safety feature was regularly tested in the unit at Oak Ridge - they literally turned off the power on the weekends and simply went home!

There are some downsides.  The working fluid requires special metals made out of Hastelloy.  But these are no longer particularly-special materials, being used in other chemical plants where highly-corrosive material is commonly handled.  They are expensive, but then again so are traditional reactor pressure vessels which require high-pressure integrity and thus special welding and inspection techniques.

Why did I just spend all this time talking about LFTRs?

Let's remember two facts from up above:

• There is 13 times as much energy in coal in the form of Thorium as there is available by burning the coal.
  
  and
• We use 863 million short tons a year of coal equivalent in gasoline and diesel fuel which is less than the amount of coal we burn now.

One final piece of information: The Germans figured out how to turn coal into synfuel - gasoline and diesel - before WWII.  This process, called Fischer-Tropsch, requires energy to drive it and is currently in commercial use in some places that have a lot of coal but little or no oil, such as South Africa.  Malaysia also has an operating plant.  Typical operating temperatures for this process are in the neighborhood of ~350C.