As you progress in creating a civilization on an alien planet, you can still use obsolete buildings. However, you must first know how to recycle materials in Lightyear Frontier.

You can recycle materials from structures by opening the Recycle function in the Build menu. When you recycle a structure, you get back all the resources you used to build it. You can dismantle anything you've built, including crafting devices, sheds, and even Upgrade Depots.

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Open the Build menu and select the Recycle Mode option to return all structures back to their resources. Once you select Recycle Mode, you will see a yellow overlay over the structures you are pointing at. Pressing the Recycle button will return the selected structure back to the resources it was made from. The amount of resources will remain the same, so if you spent five stones and three forests to build something, that is the amount you will get after Recycle.