I seem to recall a shop that specialized in selling crushed wood-based growing medium (hodagi) used for shiitake mushroom cultivation in Oita. My memory is a bit hazy as it was some time ago. The quality was excellent, and they would sell out in the spring, so I used to buy the next year's supply during the winter. I found this while cleaning out my parents' house. It's partially used, so there's probably about 40 liters left. I used it as a material for fermentation mats and for burying things. I'm also including one remaining piece of their A-grade material.