Is it possible to render out Deep images from Krakatoa for compositing?
Thanks! 
It is on the Wishlist, but it is not possible yet.
If Deep image exporting is difficult to implement, in the meantime it would be nice to have a way to create a mask for the particles from each PRT Loader, possibly with a render element, so they can be easily edited individually during compositing. As it is right now, if I have several different hair and fur PRT Loaders in a scene they all have to get rendered in the same pass if the shadow relationships are to be maintained. But then I can’t separate them easily in comp. V-Ray does this with the MultiMatte render element and it works very well.
You can create a custom channel, set it to a different value per PRT Loader, and output as custom render element.
The trouble is that flat render element passes of volumetric renders cannot be efficiently used in compositing.
Even most of the standard passes we output as Render Elements by Krakatoa are there because people insistent on having them, not because they are actually very useful in practice (they are somewhat, but not to the same extent as renders of surfaces).