Abstract: An organic digesting system incorporating a pair of digester units each of which includes an elongated, horizontally disposed frusto-conical, stationary outer drum with each outer drum including a correspondingly frusto-conical inner drum that is rotatably driven about a horizontal axis. The outer upper drum includes an inlet at the smaller end thereof and a vertical discharge conduit at the larger end thereof which communicates with the smaller end of the lower outer drum. The larger end of the lower outer drum includes a discharge outlet or conduit. Each of the inner conical drums is constructed of foraminous material to form a periphery that is porous with the foraminous periphery of the inner drum being supported from support shafts at each end thereof. The interior of the inner drum is provided with a plurality of inwardly extending agitation blades which are spaced peripherally on the interior of the inner drum and arranged in longitudinally spaced arrays.