Biochar and hydrochar derived from freshwater sludge: Characterization and possible applications

Freshwater sludge (IS) is generated in large quantities during the production of drinking water every day. It is largely underutilized, and has long been filter pressed to sludge cake and then disposed of in landfills. The search for more economical and sustainable disposal or reuse options is urgently needed. Biochar and hydrochar are increasingly popular wastes derived materials with huge potential for soil improvement, environmental remediation, and mitigation of climate change, but there is a lack of research on the production of FS derived biochar and hydrochar. In this study, biochar was produced by pyrolysis at 300, 500 or 700 degrees C for 1 h, and hydrochar was produced by hydrothermal carbonization (HTC) at 140, 160, 180 or 200 degrees C for 4 h. Proximate analyses show that the biochar has a higher carbon stability and is possibly suitable for carbon sequestration, while the hydrochar contains more labile carbon structures. The ultimate analysis indicates that the surface hydrophobicity is in the order of: biochar > hydrochar > IS. The phytotoxicity tests indicate their positive effects on germination of wheat seeds. This study provides a new treatment to reuse numerous PS and put forward the possible applications of its carbonaceous products, which is expected to facilitate a circular economy and realize the zero-waste target. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

This study investigates the production and characteristics of hydrochar and biochar, finding that biochar is more suitable for carbon sequestration, while hydrochar contains more labile carbon structures. The results also show that the surface hydrophobicity of hydrochar, biochar, and IS decreases, and they have a positive effect on germination of wheat seeds.