Let's talk trash
Disposing of garbage is a huge part of land use and industrial processing. It's also an enormously rich source of raw minerals.
However, there's a big problem: trash as a generic object can be made of iron, plastic, wood, glass, silicon... Anything that people can make, they'll throw away. Here's a way to do it. Keep a list of the total resource values that went into all garbage on the island. When you recycle garbage, select a random appropriate twice from the list and decrement it.
For example, take a settlement that has previously used up 150 tons of iron, 50 tons of copper, and 100 tons of wood. This might have a silo containing 300 tons of trash. If you have a process called "magnetic sort," you could pull out up to 150 tons of iron scrap, but no more, before the sorting center can pull out no more.
Each sorting step should produce no "depleted trash," instead probably burning the remainder into clinker, wastewater, or slag.