You beat me to it Denti, I was going to say that the problem is in the pumps/injectors.
The engine itself can indeed run on pretty much anything. I believe there have been some tests in the past running diesel engines on coal dust!!
Now that it has come up, how did Thielert solve the lubricity problem?
Did they go for one of the new ultra-low friction coatings, or did they go for a multi-stage pump with lower differential pressure to allow for looser tolerances?