You could also look at servos, which are bidirectional DC motors with limited rotational movement.
But, if it was me, I'd set up the bowl with an off-centre axle and a small counter-weight or spring. So when the bowl is full it will want to tip, and when it is empty it will want to be upright. Then (assuming it was full) you could just release a catch (with e.g. a solenoid or electromagnet) whenever you wanted it to empty.
But this really isn't a RepRap question.
But, if it was me, I'd set up the bowl with an off-centre axle and a small counter-weight or spring. So when the bowl is full it will want to tip, and when it is empty it will want to be upright. Then (assuming it was full) you could just release a catch (with e.g. a solenoid or electromagnet) whenever you wanted it to empty.
But this really isn't a RepRap question.