A digester (10) for treatment and conversion of an organic waste material to fertiliser or soil enhancer to replace humus and depleted soil, comprises: (i) a circular housing (12) for maintaining a bed of organic waste; (ii) an inlet (28) for introducing waste into the housing; (iii) an outlet (32) for discharging converted waste; (iv) a support (20) within the housing, comprising a central vertical pillar and an inwardly depending circumferential shoulder strut (22) about the inner housing circumference; (v) a support carriage (24), rotatable about the housing interior, between the shoulder and the pillar; (vi) an agitator (26) secured to and depending from the support carriage; (vii) a power source (45) for rotating the support carriage about the housing interior and driving the agitator, and (viii) a temperature sensor. The agitator comprises: (i) chain drives mounted on an upper drive sprocket, and (ii) cup like teeth on the chain drives. The chain drives are positioned in an angular relationship with the support so that the chain drive idler sprockets are positioned forward and in the advancing direction of the chain drives from the drive sprockets.    The inlet means is cooperable with a hopper (31) and transport secured to the pillar and carriage for directing incoming material to a deposit point near the outer periphery. The material is deposited near the periphery by the hopper, centrally positioned above the pillar and under the inlet, which is cooperable with a transporter (27) supported by the pillar and the carriage. The transporter comprises a continuous web belt. The support shoulder contains an upper, notched (40), gear surface (23) cooperable with the rotatable gear head (42, 44) of the carriage for positive rotation of the carriage about the housing. The outlet is a vertical concentric wall (36) about the pillar of a height sufficient to extend above the material bed.    USE -   The apparatus is used for treating organic waste and converting it to a fertiliser.    ADVANTAGE -   The apparatus can operate in continuous or intermittent mode. The agitator is self-cleaning. The apparatus automatically controls and maintains optimum agitation, the residence time and the temperature and humidity in the vessel.