Which is Natureworks PLA. I suspect a number of the types listed in this thread is as well. Eureka is nice in that they list exactly which source material it is right on the spool. Plus they use cardboard spools with the empty spool weight listed. Brilliant.
As other people have mentioned, this can be a hard problem.
However, malls are typically surrounded by massive amounts of space used for parking. There is a plan for the largest mall in my region to convert all of that land into residential spaces, 2000 apartments. The parking will be moving underground.
Seems like a decent idea to me.