Composting, as an aerobic degradation process, may be limited by insufficient oxygen supply of the involved microbes. The key question in this master thesis is to get knowledge about the range for an optimum and a minimum requirement of oxygen in the interstitial air during natural aerated windrow composting. To answer the question, based on a literature review regarding the fundamental requirements of an aeration process, the main influencing physical and microbiological aspects are presented. The findings are then applied to interpret measurement data from a real composting pile. Finally, recommendations for a suitable and effective oxygen concentration in pores of compost piles are provided.