Physicochemical properties of product liquid from pyrolysis of sewage sludge

I. Fonts, Eeva Kuoppala, Anja Oasmaa

    Research output: Contribution to journalArticleScientificpeer-review

    54 Citations (Scopus)


    Pyrolysis of sewage sludge to produce liquid for fuel use is under study as a promising way to derive value from this waste. The physicochemical properties of such a liquid were studied in this work. The total liquid and organic yields were 49 and 31 wt % of dry ash free feedstock, respectively. The gas and char yields were 32 and 20 wt % of dry ash free feedstock. The liquid was nonhomogenous, dark, bad-smelling, and sticky. By centrifugation, three phases were obtained: 11 v % top, 52 v % middle, and 37 v % bottom phase. The top phase did not contain water, had a high heating value (LHV ) 41.1 MJ kg-1) and the lowest nitrogen and sulfur contents (2.4 and 0.2 wt %) of the three phases. Some nitrogen compounds were water-soluble and could be washed out with water, obtaining a 12% reduction in the nitrogen content. The phase contained mainly alkanes and alkenes (C12-C24), triglycerides, and steroids (C27-C29). It showed miscibility with diesel in the proportion 1:10, indicating good cofiring properties with diesel. The middle phase had the highest water content (34 wt %), and the lowest heating value (LHV ) 15.5 MJ kg-1). It contained mainly water-soluble compounds such as amino-sugars, acids (C3-C9), phenols, nitrogen-containing compounds (some of them with thiol groups), and levoglucosan. The bottom phase had low water content (12 wt %) and high heating value (LHV = 30.6 MJ kg -1). Most of it (57 wt %) was water-insoluble material. It contained phenols, fatty alcohols, nitrogen-containing compounds (some of them with thiol groups), fatty acids (C12-C18), triglycerides, and amino-sugars. In all of the three phases the amount of GC-eluted compounds was low. The high nitrogen and sulfur contents of the middle and bottom phases make their use as a fuel oil difficult without any secondary treatment. These phases could probably be used as fuel for a lime kiln.

    Original languageEnglish
    Pages (from-to)4121-4128
    JournalEnergy & Fuels
    Issue number8
    Publication statusPublished - 20 Aug 2009
    MoE publication typeA1 Journal article-refereed


    • sewage sludge
    • pyrolysis
    • pyrolysis liquid
    • waste
    • waste to energy


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