Pyrolytic mechanisms of typical organic components of sewage sludge in the presence of CaO: Polysaccharides, proteins, and lipids

Xiaoxia Yang; Chao Yu; Butera Hassan; Lun Zhang; Changkai Wang; Huan He; Bin Huang; Xuejun Pan

doi:10.1016/j.scitotenv.2023.166020

Pyrolytic mechanisms of typical organic components of sewage sludge in the presence of CaO: Polysaccharides, proteins, and lipids

Sci Total Environ. 2023 Nov 25:901:166020. doi: 10.1016/j.scitotenv.2023.166020. Epub 2023 Aug 2.

Authors

Xiaoxia Yang¹, Chao Yu¹, Butera Hassan¹, Lun Zhang¹, Changkai Wang¹, Huan He¹, Bin Huang¹, Xuejun Pan²

Affiliations

¹ Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming 650500, China.
² Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming 650500, China. Electronic address: xjpan@kust.edu.cn.

PMID: 37541510
DOI: 10.1016/j.scitotenv.2023.166020

Abstract

The addition of CaO could facilitate the conversion of sewage sludge (SS) from waste to high-purity syngas. The pyrolytic characteristics of SS are a comprehensive manifestation of polysaccharides, proteins, and lipids, while the influence of CaO on their pyrolytic characteristics is rarely reported. This study conducted a thorough investigation into the pyrolytic mechanism of starch, protein, and lipid in the presence of CaO by analysing their thermal behavior, gaseous products, liquid tar, and residual char. The findings from TGA, GC, GC-MS, and FT-IR analysis indicate that the addition of CaO catalytically lowers the pyrolysis temperature of starch, protein, and lipid components and promotes their conversion into small molecules, resulting in increased syngas production. Moreover, the combination of char with the carbonation and calcination cycle of CaO leads to a significant boost in syngas (H₂ and CO) yield, with up to 3 and 10 times increase from starch and protein, respectively, and a higher syngas selectivity of up to 65 %. The study also identifies those polysaccharides and proteins are the primary sources of syngas. This study can provide further insight into SS pyrolysis for syngas production in the presence of CaO and the necessary parameters to predict the pyrolysis behavior of SS in industrial applications.

Keywords: CaO; Lipids; Polysaccharides; Proteins; Pyrolytic mechanism.