I've been searching ball valves using gravity and haven't found anything yet. The only thing I can think of so far is to build a box in advance of the 4" pvc pre-drum and post-toilet. In this box I would put a thick wire mesh on a small levered platform of sorts that would hold the waste until the liquid passes but I'm trying to figure out how to automate this from the toilet and using gravity.
I've already been to the physics forums. They don't want to talk about eco waste and gravity in the same sentence I think.
I thought of getting an rv toilet with a floor levered ball flush and connecting to that mechanism.