Extraction - Breaking down hard plant material / bark into fine powder (flour consistency)

[genaro]

ok, here's a question swim is wondering about since a long time: many webshops sell bark or root bark from plants (which are very hard) in the form of an extremely fine powder, meaning flour consitency.
This can be achieved with a powerful blender but this methods takes lots of time (all the plant material isn't crushed into such a fine powder within the few first minutes of blending), moreover this just end up killing your blender (swim destroyed several blenders doing so, even when allowing the blender to cool down for 5 minutes after every minute of blending).

So, does any one know what kind of apparatus webshop use to crush hard plant material fast and easy into flour consistency powder?

...I'm pretty sure they don't waste their time with blenders, they are obviously using something more appropriate (considering they have to crush big amounts of plant quite often)