When adding Energy to the game ecological cycles could be a fine enhancement.
Right now we produce Carbon out of Water, light and time. But there could be also Carbondioxid in the atmosphere of planets which is “refilled” by some of the production plants and by energy plants… Waste from production and consumption incl. dirty water could be also a good cycle… and energy or light can also be used to produce pre-chems such as Syngas from solar plants out of gases such as Carbondioxid in the atmosphere.
Basically the idea is that players also create resources of planets.