How can I support a joist length of 9 meters without steel?
I just checked some Ontario tables.   For an Attic, not accessible by stairs (i.e. not used as living space,   a 2x12 every 12" can span 32 ft.  But you can't put anything above it.

I've found nothing in the tables that allows a 30 ft span supporting a floor.  

While this doesn't mean it can't be done, it means you need to consult with an engineer, and pay for a proper design.