Biochar Derived from Sewage Sludge as a Soil Amendment: The Impact of Pyrolysis Temperature on Product Characteristics Along with Heavy Metal Environmental Risk

The purpose of this research was to investigate the impact of pyrolysis temperature on the properties of biochars fabricated by sewage sludge. Increasing pyrolysis temperature from 300 to 900°С led to an increase of biochar pH between 8.4–11.8, ash content 60–75% as well as specific surface area 68–161 m 2 g –1 . At the same time, there were reduced H, O, C, S, N contents, the H/C and O/C ratios. An increase in pyrolysis temperature enhanced the content of metals in biochars and reduced their bioavailability. XRD analysis confirmed a higher degree of metal-containing phases of formation in biochar with increasing pyrolysis temperature.