It always bothered me that there is no use for iron or niter past the industrial. So, being the production monger I am, I cobbled together a pair of buildings to plug that gap. The goal is to give you something to do with these resources and also provide a motivation for players to continue to seek them out in the late game.
Steelworks - unlocks at Steel (duh.) Provides +2 production for each specialty district in this city, and additional production when powered.
Consumes 2 Iron per turn.
Chemical Plant - unlocks at Chemistry. Provides production to every farm, plantation, pasture, and few unique improvements in the city. Additional food when powered. Consumes 2 Niter per turn.
There are also projects to convert a factory, steelworks, or chem plant into the others, as well as civilopedia entries to help you history nerds justify their inclusion.
These buildings are strong, but realize that you can only have one per relevant mine in your empire. On standard settings, that's not a lot. In that sense, they are intended to be somewhat balanced.
I made this back in 2019, but never posted it because the building models are simply the standard factory. I have overcome this shame, hence I am posting such a low effort mod in my sig. Maybe people will find it fun
The consumption of resources by buildings is supported by the game but not the UI; so while the math and everything is correct, you will not see a breakdown about how much buildings are using. You need a fixed amount of the base resource (10 on standard speed) to build or convert to one, so you cannot cheat and spam these endlessly.
As more civs and patches are released under the New Frontier Pass, I may need to update some of this. Just bug me about it!
Strategic Industry 1.0
Alternate Factories that consume obsolete resources