[q=Squall of SeeD]Also, the Energy Packs used to power everything were some derivative of organic material we're told, but they obviously contain some spiritual properties in that one of the Eight Spirits was an Energy Pack.[/q]Yep; in the film, we're told that they farm micro-organisms in order to extract their bio-etheric energy ('spirit' energy) and use it as a source of power.

(SPOILER)When the phantoms invade New York City, they travel through the energy conduits, riding the energy pathways like a surfer on a wave.

It's a great concept, and the film dealt with it well, although in too little detail. I prefer FFVII's handling of the matter.