Medium-hot take: sustainable cities really wouldn't need that much steel at all. The optimal height for residential buildings is about how many stories you can climb without being winded, and you can do this with timber and brick.
Cities will never be sustainable if they replicate the paradigm of enabling each individual's presumed desire to accumulate personal or private property to fill every need. Switching to universal access to everything, rather than ownership, is the biggest step. Once you do that, dwellings don't need to be as big, yards can be pooled together, there will be a shorter distance to everything, and production requirements for virtually everything will dramatically drop.
You can have a sophisticated and sustainable city with mostly 1700s-level technology.
Medium-hot take: sustainable cities really wouldn't need that much steel at all. The optimal height for residential buildings is about how many stories you can climb without being winded, and you can do this with timber and brick.
Cities will never be sustainable if they replicate the paradigm of enabling each individual's presumed desire to accumulate personal or private property to fill every need. Switching to universal access to everything, rather than ownership, is the biggest step. Once you do that, dwellings don't need to be as big, yards can be pooled together, there will be a shorter distance to everything, and production requirements for virtually everything will dramatically drop.
You can have a sophisticated and sustainable city with mostly 1700s-level technology.