In the rectangular agitated in-vessel composting bioreactor, the prepared waste is placed in the infeed conveyer. As the extraction conveyer moves, it mixes the compost. Oxygen is supplied by forced aeration through the air plenum and blowers at the bottom of the bed. This aerates and prevents the composting material to heat up. Tumbling or mixing occurs at regular intervals to agitate the material, break up clumps and maintain porosity before discharging it in the outfeed conveyer. After a retention time of 6-12 days in the bin, the material is windrowed for 1-2 months i.e. the curing period until stability is reached. The horizontal rectangular tank is well suited for sewage sludge, MSW and mixtures of MSW and sludge (Tchobanoglous et al., 2002).