The big question is, why haven't the EU policymakers done this little bit of arithmetic, or hired someone who can?

The arithmetic might have spoilt the show, that's why --- at least from the perspective of the powerful biofuel-pushing agri-lobby. And Piebalgs isn't really engaging in dialogue: he is churning out the party line. Including the insinuation that opposition to biofuels is a symptom of the Communist mindset.

We've had the Fidel Castro tune song twice already in his blog:

Fidel Castro is a Commie thug
Fidel Castro is opposed to biofuels.
Other people are also opposed to biofuels.
Therefore, nudge-nudge, those other people are quite possibly Commie thugs as well.

I fear Commissioner Piebalgs is trying to sell a product rather than debating whether the product is worth selling at all. Still, his blog is uncensored, and we should make the most of the opportunity to enlighten his readers, even if he himself has a closed mind.

Cuba / the Castro-system is one real world place where “we the world” can get real-time information as to whether bio-fuels would work or not!

B/c Cuba would go after bio-fuels years ago, if it was possible, no? Sure they would and probable have tried, and concluded accordingly: Not possible.
If 1 square meter returned say 1-2 liter of bio-fuel, just like that, without any other inputs – it would have driven Cuban society as a showcase society for the transition to such ways, for "the rest of us". BUT sadly this is not the case.