Hydrothermal carbonization of pulp and paper industry wastewater treatment sludges - characterization and potential use of hydrochars and filtrates

Anna Hämäläinen, Marika Kokko, Viljami Kinnunen, Tuomo Hilli, Jukka Rintala

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Abstract

The pulp and paper industry's mixed sludge represents waste streams with few other means of disposal than incineration. Hydrothermal carbonization (HTC) could be advantageous for the sludge refinement into value-added products, thus complementing the concept of pulp and paper mills as biorefineries. Laboratory HTC was performed on mixed sludge (at 32% and 15% total solids) at temperatures of 210–250 °C for 30 or 120 min, and the characteristics of the HTC products were evaluated for their potential for energy, carbon, and nutrient recovery. The energy content increased from 14.9 MJ/kg in the mixed sludge up to 20.5 MJ/kg in the hydrochars. The produced filtrates had 12–15-fold higher COD and 3–5-fold higher volumetric methane production than untreated sludge filtrates, even though the methane yield against g-COD was lower. The increased value of the hydrochars in terms of energy content and carbon sequestration potential promote HTC deployment in sludge treatment and upgrading.

Original languageEnglish
Article number127258
JournalBioresource Technology
Volume355
DOIs
Publication statusPublished - Jul 2022
Publication typeA1 Journal article-refereed

Keywords

  • Anaerobic digestion
  • Carbon sequestration
  • Energy recovery
  • Hydrothermal carbonization
  • Pulp and paper mixed sludge

Publication forum classification

  • Publication forum level 2

ASJC Scopus subject areas

  • Environmental Engineering

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