It is exactly 16 for both Black and White. The reason is that there are 15 pieces to be taken, so at least 15 moves. This minimum is achieved if you capture a piece in each move.
Now, Black can not capture anything on his first move, no matter what White plays. The earliest is move #2, hence the minimum number of moves becomes 16. @bb_gum234, just showcased such a sequence of moves.
Similarly, for white.
I was wondering if anyone has ever looked at what's the fewest moves in which a player can give up all their material (assuming they just throw material away in a 'cooperative' way)? I have absolutely no idea. When I make early pre-move blunders in bullet games I sometimes try to just throw away as much material as I can as quickly as possible just for fun. I wonder what's the quickest possible way to end up with just your king left....