Utilization of Sewage Sludge-Derived Pyrogenic Material as a Promising Soil Amendment

Abstract

The use of advanced treatment technologies such as pyrolysis and carbonization of bio-waste materials has the promise to develop coupled solutions for organic C and P problems in the future of food processing. Sewage sludge-derived pyrogenic materials that are applied to the soil system contain notable levels of P (1–20%). However, only a small portion of total phosphorus is available for plants. Therefore, our study assessed the pretreatment of sewage sludge with Na2 CO3 and subsequent pyrolysis at 400◦ C and 500◦ C for the production of MPCM400 and MPCM500 as potential alternatives for inorganic P fertilizers. Non-pretreated sewage sludge-derived pyrogenic carbonaceous materials (PCM400 and PCM500) were produced as controls. The derived materials obtained by slow pyrolysis at a residence time of 120 min and pyrolysis temperatures of 400◦ C and 500◦ C, were analyzed by determination of electrical conductivity (EC), pH, elemental analysis of total C, H, N, scanning electron microscopy (SEM) and total concentrations of P, Cd, Fe, Pb and Zn. PCM400, PCM500, MPCM400 and MPCM500 were characterized by analysis of total 16 US-EPA (U.S. Environmental Protection Agency) PAHs by a toluene extraction procedure. Additionally, PCM400, PCM500, MPCM400 and MPCM500 were tested by a germination test with cress seeds (Lepidium sativum L.) and a short-term rye seedling test. Total C concentrations were raised in the order: MPCM500 < MPCM400 < PCM500