Fascinating idea. I've never thought of that. Most home brewers lucky enough to live near farms can give their spent grain directly to the farmer right after brew day is done. Like you say getting the moisture content down to 10% would be the only challenge in order pelletize your spent grain. If you have the outside space you could spread out your spent grain in a thin layer on a tarp in the sun, which I assume Greece has plenty of! Be sure to stir it around periodically. Otherwise you would have to use your oven or similar to dry them, which would increase the cost of pelletizing. You could use before and after weights to determine moisture content. Keep us posted if you proceed with this option. It sounds very interesting.