Yes, coal will produce iron oxide spheres but how many tons of coal has to be burned to produce one ton of these spheres? At what temperature?
Who says any "tons of coal" must be burned to produce a ton of iron-rich spheres? Certainly not me. My point is that extraordinarily high combustion temperatures are not required to produce them.
How many floors of "office contents" must be burned, and at what temperature, to produce a pound of iron spheres?
I don't know, but you could figure it out if you wanted. Start by researching the plant sources of paper pulp, and the typical concentration of ferritins in those plants. That would give you a rough idea of the concentration of ferrihydrites in paper. Then do the same for typical office wood products. Then look at iron oxide and iron sulfide contents of other expected office materials. (In most coal, most of the iron comes from FeS, so any FeS in other combustible materials would be a likely additional source.) Don't forget to figure in ambient environmental "background" sources such as construction activities and city traffic. This would require somewhat more effort than citing quotes mined by other truthers. Get to it, if you want to make an argument based on insufficiency of office contents at the site.
It has not been demonstrated that normal office fires produce a significant amount of iron spheres.
It has been demonstrated that unusually high combustion temperatures are not required to produce iron-rich microspheres. Therefore the presence of such microspheres is not evidence of unusually high combustion temperatures. That is why no one with any relevant expertise in fire investigation finds the iron-rich microspheres at ground zero to be unexpected or significant.
Respectfully,
Myriad
