I don't use chemicals either, to me its the same as flushing money down the toilet.
There is no way I can dump in my septic, its behind the house, a long ways from where I park the RV next to the garage. So, I built a homemade septic in the woods near the RV. I used two 55 gallon drums, connected them so I had a solids/digester, and clarifier, then a small 20' leach/drain field with perf pipe. Many years ago I worked for an outfit putting in septic systems, and had an idea of how they work. I have a backhoe, it was easy.
Its real nice to just leave if there is a line at the CG dump station. Or, if boon docking where there aren't any place to dump.