I've had the same run for ages. Concrete base, wisteria overhead, decent air flow. I always did pine shavings, but I really notice when I turn it into the compost, I'm not getting those shavings to breakdown as quickly as I'd like. But directly between the run and the compost is a ginormous pile of leaves I've been slowly adding to the compost! Duh!! I feel dumb for not thinking of this earlier, but outside of issues I've heard of with them getting moldy etc, they get wet and dry out just as much as the shavings and they're free! Anyone have any experience with using leaves in the run? I feel like I need to build up the volume for them somehow. Should I cover the leaves with a tarp to keep them dry?