In the 70s I read about a "Home Waste Digesting" system that produced methane gas and a solid residue that could be use as compost in your garden.
The methane was use to power a closed water system steam generator for electricity. The generator was low compression and any parts could be repaired/replaced in a good home workshop.
All biodegradable waste went into the system: waste water and the usual garbage. Not sure if the system had any liquid output which needed disposal. It was touted as a pretty much self sustaining system.
Have to check to see if anything like that is available.