NOVELTY - Preparing sterile soil substrate from composted animal feces, comprises: separating the feces into a solid and liquid phase; preparing the solid phase of feces in air circumstance in a leased form; carrying out a first phase of aerobic material conversion, which includes an initial composting process; carrying out a second phase of aerobic material conversion, which includes a fungal phase and subsequently an aerobic bacterial phase; repeating the second phase of the aerobic material conversion until the temperature after the conversion does not exceed to 70 degrees C.    USE - The sterile soil substrate is useful as slow-release fertilizer. No biological data given.    ADVANTAGE - The sterile soil substrate exhibits high degree of purity and good water storage capacity. The soil substrate is free from plant pathogens, heavy metals and toxic substances.    DETAILED DESCRIPTION - Preparation of sterile soil substrate from composted animal feces by aerobic material conversion, comprises: separating the feces into a solid and liquid phase, where the solid phase contains 20-50 wt.% of dry matter; preparing the solid phase of feces in air circumstance in a leased form; carrying out a first phase of aerobic material conversion, which includes an initial composting process, where the temperature of the solid phase is reduced to at least 70 degrees C after the completion of the initial composting process or the oxygen content is reduced to below 5% or the carbon dioxide content is increased to 18%; carrying out a second phase of aerobic material conversion, which includes a fungal phase and subsequently an aerobic bacterial phase, where the temperature of the solid phase is reduced to at least 70 degrees C, after completion of the bacterial aerobic phase or the oxygen content is reduced to below 5% or the carbon dioxide content is increased to 18%; repeating the second phase of the aerobic material conversion until the temperature after the conversion does not exceed to 70 degrees C, where the density of the starting material during the material conversion process is 220-380 kg/m3, the dry matter of the solid phase is monitored to adjust the dry matter content during the conversion and the liquid content of the circumstance is increased to above 48 wt.%.