@Hvogt:
I think the first reply, from @safelife, covered the subject well. If this is of major importance to you, I'm certain that you can search a bit and find the regulations and/or call the regulating authority in Germany. Good luck...
I too am unable to instantly quote any U.S. or Euro regulation on the subject, but I've understood for years that the practice is forbidden. I could be very wrong here, but in some places it MAY be possible to reuse the fuel, but ONLY in the SAME airplane. As for returning the fuel to the general supply, don't even think about it!
One can easily understand why discarding 2000kg of fuel would cause the bean counters a little stress, but they will just have get over it. IMO it is not a stretch to consider this as a Safety of Flight issue.
Last edited by No Fly Zone; 1st Feb 2016 at 06:07.
Reason: Added Information and Suggestion