Hi,
johnwasser:
I think a good alternative would be a set of LEDs and light sensors at the FULL ENOUGH level of the waste bin. The Arduino can light the LEDs in sequence and check that all of the sensors detect the light. If any path is blocked it means there is some object at or above the FULL ENOUGH line.
A laser distance sensor will only work on one point. Three LEDs and three sensors can check nine lines across the opening.
Like a light curtain..
Tom.. 