In most grids of this world renewable power is on the rise. One building block of this are biomass fired power stations with their distinct advantage to produce electricity on demand. The change of fuel from coal to biomass i.e. green or black pellets not only makes electricity production carbon neutral, it will also allow existing assets such as coal fired boilers to be used for the new fuel. In several Scandinavian countries but also in countries of Europe as well as the UK biomass plants are to be found these days. Besides providing carbon neutral electricity their aim is also to provide baseload power and stabilize the grid with their conventional and large turbo gen sets. Besides new mills especially designed for biomass cutter and hammer mills there is high interest in using the existing vertical spindle mills including the existing piping in order to feed the firing systems. Besides the biomass storage the milling section is one of the big efforts one has to take in order to convert a unit from coal to biomass.