We removed 12" x 12" vinyl tiles form hardwood floor but there are adhesive left on the floor. We tried sanding the floor with 24 grit sand paper to see if the adhesive will sand off but that just clogged up the sand paper. What is the best way to remove the adhesive from the hardwood floors before we sand the floor? Where can we buy good bio-degradeble adhesive removers (if any of them exist)? Thank you.

Buy a couple of big bottles of mineral spirits, or charcoal lighter fluid. Use it to remove the glue residue.

We just finished removing our kitchen floor and were able to get the glue/paper left after removing the top layer. First of all, we removed the top layer using an impact wrench with a 4" heavy duty scraper mounted to the small scraper using pipe clamps. Pealed up the top layer in no time.
Second, we used our wallpaper steamer on the floor allowing it to soak long enough that the glue and paper came up with little or no effort.
The trick to the steamer is to figure out how long to leave it until the glue loosens up.
Good Luck ...

I forgot to mention that we tried every solution recommended through various threads and none of them worked. The steamer was the cleanest and easiest.