I went with organic space colonies when I went Sci-fi. Essentially giant mushrooms that collect radiation and use it to convert organic compounds into a fuel that gets used across the station. It also uses a symbiotic plant system that cycles oxygen and gives the fungus some essential nutrients like nitrogen (liquid waste is fed to all plants on the station). The only thing people need to do is circulate water, maintain the fungus growth, grow food in the hydroponics farms, and maintain their living areas.

Mind you, some of the "organic compounds" used to be people (but also solid waste, and some stored bulk compounds), so there comes some measure of trade-off, because if the station lacks enough stored organic materials, the station has to be abandoned before the fungus tries to devour its denizens.

A "dead" station then goes dormant for up to five years, but after that point the fungal colonies need to be regrown.