Abstract: A method for estimating a parameter relating to solids recovered from a wellbore may include drilling a wellbore using a bottomhole assembly; conveying solids in the wellbore to a surface location using a drilling fluid; separating the drilling fluid from the solids using at least one shaker; conveying the separated solids by using a conveyor; and continuously dropping the solids into a solids evaluator positioned vertically above the dryer. The solids evaluator includes a chute having a vertically aligned bore in which the dropped solids reach a constant velocity, a sensor assembly generating a microwave field in a section of the chute where the dropped solids have the constant velocity, and a control unit in signal communication with the sensor assembly. The control unit estimates a mass flow rate of the solids based on the generated signals.