Well it
was called that, but now goes by the way more catchy term "fecal sludge."
I saw a show not too long ago on building off grid homes that were earth friendly. These people had an additional basement just for power equipment and these huge polymer tanks. It was a septic system turned fertilizer production setup, where over the course of months sewage was staged in these tanks, which also contained red worms. I think the final tank may have used heat, but what came out for the garden looked like something you'd spend money on at Lowes.
Gray water system for watering things, heat pumps, solar and wind power, high capacity below ground water storage. Very cool, lots of ideas for when I do something similar.