To lift an object x meters it is necessary to expend, at a minimum, an amount of energy corresponding to the increase in that objects potential energy associated with the increase in height. When putting the object down, returning it to the position it was moved from, its potential energy with respect to gravity returns to the original amount. However, this potential energy is not returned to the person who did the lifting. On the contrary, putting an object down gently requires additional energy to be expended to slow what would otherwise be a free fall.
Can any organism convert gravitational potential energy to chemical energy? Is it at all biologically feasible?