It could easily be 100% gravity after you pump it up to height.
This image shows one type of connection you might use (between the clean-outs).
Word of caution, be sure you want to open up a waste pipe.
Also, such a move would be highly frowned upon by local inspectors in Mass. Not sure about where you are.
I didn't even get around to asking where your super nutrified waste water would end up??
Not always great for a public system, and I would not pump it into a private system. That will shorten its life.