The sludge management of many wastewater treatment plants in Poland has not been properly solved as yet. The exploiters and designers have to cope often with the dilemma of choosing the method of processing and neutralizing sewage sludge. The method discussed in the article is only one of the options that fully fits in the trends of implementing good practices in the management of sewage sludge. It is a process technologically and economically effective and environmentally friendly. It contributes significantly to minimizing the amount of sewage sludge and allows the production of organic fertilizer instead of waste. The work discusses the quality of sewage sludge after autothermal thermophilic stabilization (ATAD). The results of investigations of the reaction of sludge, dry mass, dry organic matter, content of biogenic substances, calcium and magnesium compounds and heavy metals were analyzed.