Co-pyrolysis of sewage sludge and rice husk/ bamboo sawdust for biochar with high aromaticity and low metal mobility

Jin ZHANG, Junwei JIN, Minyan WANG, Ravi NAIDU, Yanju LIU, Yu Bon MAN, Xinqiang LIANG, Ming Hung WONG, Peter CHRISTIE, Yan ZHANG, Chengfang SONG, Shengdao SHAN

Research output: Contribution to journalArticles

Abstract

Blending waste biomass for co-pyrolysis is generally regarded as a promising method for reduced-volume, value-added, and hazard-free treatment of sewage sludge. Hence, a comparison was made of the co-pyrolysis of sewage sludge with rice husk and with bamboo sawdust (1:1, w/w) at 400 and 700 °C and the properties and behaviors of selected metals in the corresponding biochars. Biochar produced by co-pyrolysis with both biomass wastes had larger (5 × 5 rectangle) aromatic clusters than did the sewage sludge biochar (4 × 4 rectangle) using the rectangle-like model on the basis of biochar molar H/C ratio, indicating increased aromaticity of the co-pyrolyzed biochars. Moreover, the molar O/C ratio of the sewage sludge-bamboo biochar was much lower than that of the sewage sludge-husk biochar, especially after pyrolysis at 700 °C (0.02 vs 0.27), suggesting greater recalcitrance to ageing. Co-pyrolysis of sewage sludge with husk invariably resulted in a higher percentage of metals studied in the residual fraction than co-pyrolysis with sawdust at the same temperature, leading to a lower risk index (14.2) because of the maximum metal encapsulation in the sewage sludge-husk biochar at 700 °C. Overall, co-pyrolysis of sewage sludge with husk provided higher metal immobilization but apparently lower biochar stability than co-pyrolysis with sawdust. These results provide an alternatively practical strategy for the safe disposal of sewage sludge and biomass wastes. Copyright © 2020 Elsevier Inc. All rights reserved.
Original languageEnglish
Article number110034
JournalEnvironmental Research
Volume191
Early online dateAug 2020
DOIs
Publication statusE-pub ahead of print - Aug 2020

Citation

Zhang, J., Jin, J., Wang, M., Naidu, R., Liu, Y., Man, Y. B., . . . Shan, S. (2020). Co-pyrolysis of sewage sludge and rice husk/ bamboo sawdust for biochar with high aromaticity and low metal mobility. Environmental Research, 191. Retrieved from https://doi.org/10.1016/j.envres.2020.110034

Keywords

  • Sewage sludge
  • Co-pyrolysis
  • Waste biomass
  • Biochar aromaticity
  • Metal immobilization

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