1000C isn't all that hot. Peak combustion temperatures in an IC engine might be much greater than that.
As PC points out, it's not so much the temperature as the amount of waste energy. 70% efficiency is pretty impressive.
That's below the temp where NOx forms in IC engines for instance! - Not such a problem for Fuel-cells of course.
With potentially only 30% of (probably at a low-heating value) wasted heat being left over (A well insulated casing for the cell would ensure these high efficiency numbers) I don't think that we ought to spend too long worrying about picking up that spare
energy.... [might be enough left for the driver to run a nice bath at the end of his commute ]
Syhprum, I think there are quite a number of articles on Direct Carbon Fuel Cells, and several variations in their operation.
So basically, forget the Hydrogen economy (that the Oil giants are keen to lend prophesy to; can't imagine what their reason is!!
) and ready yourselves for the Carbon economy! ('oh how very 19th century!!'...who said that?!)
Oh, yes and also this type of technology lends itself much better to Carbon Sequestration; if as is probably likely sequestration will have to play a fairly big role in any serious efforts of global carbon reduction.