
An external combustion engine (aka steam engine) can be fed with human flesh as easily as it can be fed with coal. That doesn't make it alive.
Don't confuse the consumables with what the consumables are powering.
Aside: since 3e vampires gain temporary hp by feeding on blood, do they gain temporary hp with a ring of sustenance? I'm inclined to say "of course not". But if vampires metabolize blood, then I'm less certain....
The Liber mortis provides canonical answers to ghoul and vampire hunger if anyone cares.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.