Bynum is definitely not trash. In the 7 games near the end of last season when Kobe was out and Bynum was featured on offense more this is what he did:
Game 1 – 23, 18 boards (7 offensive)
Game 2 – 18, 11 boards (4 offensive)
Game 3 – 16, 30 boards (8 offensive)
Game 4 – 30, 8 boards (3 offensive)
Game 5 – 23, 16 boards (5 offensive)
Game 6 – 21, 7 boards (0 offensive)
Game 7 – 31, 9 boards (1 offensive)
7 wins, 2 losses during that span (and that includes wins over the Spurs, Nuggets and Mavs.)
That's good for an average of 23 and 14 and I don't think it's out of the realm of possibility that he'll average somewhere close to that for the season now that he'll be a focal point of Philly's offense.