Large amounts of sewage sludge are generated in the process of sewage treatment. Sewage treatment and sewage sludge treatment and handling inevitably cause the problem of gas emissions and unpleasant smells. Degradation of organic matter results in the emissions of gases with an unpleasant smell (NH₃, H₂S, etc.), as well as greenhouse gases (CO₂, CH₄, N₂O). The processes of biodegradation occur in nature and under artificial conditions, during composting. Our analysis covers the experimental results of sewage sludge composting by investigating NH₃, H₂S, CO₂, and VOC emissions. The experiment used surplus sludge from sewage treatment facilities that were dewatered with centrifuges (75.9% humidity). Additional materials applied included wood bark, sawdust, peat, and a grass layer (a lawn roll). Composting was performed in the “facilities” simulating a composting site.