**Abstract**

The treated sewage sludge is a smart material that provides sustainable use of energy and material that can be adapted to the needs of modern human life. Pyrolysis is one of the waste recovery operation that enables the generation of various useful groups of substances from treated sludge, which can then be utilized separately by final energy and material recovery processes: (i) solid residue (pyrogenic material), (ii) liquid fraction (bio-oil), and (iii) non-condensable gas. Those fractions are the basis for fertilizers and alternative fuel or new chemicals production. The chapter combines data on the quality of treated sludge as a case study of an urban wastewater treatment plant (UWWTP) with the capacity of 360,000 population equivalents (PE). The analytical results of dried anaerobically treated sludge over a 10-year period (from 2010 to 2020) are evaluated with respect to the limit values from directives, resolutions, guidelines, and national legislation related to specific processing procedures and quality of the final product. The data provide a comprehensive insight into the basic properties of treated sludge and allow thoughtful use of this smart material for WtE processes, organic matter material conversion, and agricultural use in terms of protecting the environment and human health.

**Keywords:** circular economy, fertilizer, incineration, pyrogenic material, pyrolysis, sewage sludge, solid residue, urban wastewater treatment plant, waste to energy
