Our study would like to draw attention to an insufficiently investigated question: how human excreta and its different treatment methods are related to climate change. Human excreta is part of the biological cycle. Its CO2 content gets released to the atmosphere to some degree according to the treatment methods used. 40 55% of faeces’ and 11-17% of urine’s dry matter content is carbon (in the form of organic compounds). According to this, approximately 21-57 g/person carbon bound in organic compounds is produced daily, which means an emission of 58-183 million tons of carbon in the world annually in the form of human excreta. The environmental load of the widely spread flush toilet based water infrastructure is significant. However, neither the degree of CO2 emission caused by collection and treatment of waste water, nor wasting of organic and nutrient content of excreta are properly studied. Our study highlights the emission of CO2 caused by the energy demand of sewage water collection and treatment, by the oxidation of organic compounds of human excreta and by burning of methane produced as a result of anaerobic treatment of waste water sludge. Finally the possibility of utilization of human excreta by direct composting is presented, which technology has not significantly spread in the world yet.