MSW or agricultural biomass waste processing utilizes high latent heat and pressurized fine steam particles for spontaneous release of vast energy onto the surface area of waste particles upon contact within the metal chamber. Pressurized nano-sized saturated steam is pumped into the processing vessel at temperatures over 160°C. The pressure in the vessel is maintained within 8 bar for a 30 minutes retention time to fully breakdown longer lingo-cellulosic structural chains to shorter ones via a de-polymerization process. The process also achieves high microbial kill; even lowering the heavy metal reactivity; deeming it safe for agricultural application. The axial rotation of the chamber and the internal fins tumble the content repeatedly. The result is physical particle degradation and greater uniformity for steam contact surface. The primary product from the hyperbaric hydrothermal chamber is short chain cellulose fibers and carbonized biomass particles. The biodegradability of the waste is increased by the de-polymerization process; making it ideal for further anaerobic microbial digestion towards maturing phase. The “de-polymerization” process causes paper and other fibrous material to disintegrate into fibrous mass while ligno-cellulosic structures will be bio-converted for subsequent anaerobic microbial degradation. The process reduces the volume of the waste by ~60-70%. After “de-polymerization”, the steam flow is stopped and the pressure vented via a condenser. After depressurization, the chamber door is opened and by rotating the vessel, the “processed” char material can be discharged. The high moisture char is then conveyed to a continuous feeding saperator machines to screen other non organic matters.