In article , sw
writes

Why? This is the first I've heard of it.

As I understand the matter, it's because cement requires relatively
large amounts of energy to burn the lime/chalk and again to transport
the result, especially if it's bought as ready-mix (I doubt concrete
post manufacturers do this, though).
Wood is better :-)

In Denmark the cement factory's supply the local community with their
excess heat which the householders use for central heating.
--
David