I finally found a link to what I had seen for the recirculating toilet:
https://www.thetford.com/wp-content/...3-Vent-Kit.pdf
It's nothing but a vent kit. I had thought of installing an inline fan for it, but you've outdone it!
I've seen so many abandon the recirculating toilet because of the smell. I knew something like this could work, and you've proven it. This will likely be my summer project for next year.
Now, to prevent clogs. That is a topic from a different thread.