Well the answer is that you need to buy the right machine, and you will be delighted with the results. The right machine is called a "double gear reduction". It uses a gearbox to multiply the power of the motor to the "working" part of the machine. It's like riding your bike up a hill, you shift to a gear that is easier to pedal. Wood is harder than green biomass, it takes more power. Just using a larger machine with a bigger motor does not neccessarly work, it is all about the horse power vs the size of the machine. Let me be clear, yes you can pedal uphill without down shifting, but it a lot harder than it needs to be. Likewise you can use a single gear reduction to make all wood pellets, it just a lot harder than it needs to be too.