Process for composting decaying material of organic waste and/or sewage sludge in two processing steps

A process for compositing decaying material selected from the group consisting of organic waste or sewage sludge in two processing steps comprising:

• (a) treating the decaying material to achieve a decayable C/N ratio and then continuously and countercurrently aerating the decaying material in the first processing step so as to decay the material both anaerobically and aerobically, wherein the decaying material is brought into a first vessel from above and discharged from the bottom in such a manner, that each particle of the column of material consisting of decaying material passes through the first vessel within 7 to 14 days and the column of material is aerated countercurrently and continuously from below in such a manner that different heat layers and oxygen layers are formed within the column of material and thereby support a specific distribution of aerobic or anaerobic bacteria throughout said column which effect decaying and render it biologically active;
• and
• (b) directly introducing this continuously aerated material to the second processing step by transferring the biologically active material from the first vessel to a second vessel which is closed to the atmosphere at a rate such that it passes through the second vessel within 14 to 20 days and is aerated discontinuously during this time at intervals in such a manner that only aerobic processes take place in the column of material present to mature the decaying material in said second vessel.