Without any chemicals you can dump into any toilet with good conscience, regardless of the waste water treatment downstream.
The SOG fan is a common aftermarket modification over here. The way the toilet is set up in my camper makes it difficult to install. Here is a link to their english site:
https://www.soguk.co.uk/what-is-a-sog/I had a classic black tank toilet in our first camper. It was a bit inconvenient at the end of a trip, as we needed to find a suitable dump station before parking the rig at home. With the cassette, we just pour it into our home toilet.
If you are doing many short trips and frequently move camp, it is very convenient and IMO the better alternative.
If you usually stay put in one place for some time, maybe even with full hookup, a cassette is probably not for you.