Hydrothermal carbonization of industrial mixed sludge from a pulp and paper mill

Mikko Mäkelä*, Verónica Benavente, Andrés Fullana

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

58 Citations (Scopus)


Mixed sludge from a pulp and paper mill was hydrothermally carbonized at 180-260°C for 0.5-5h with the use of HCl or NaOH for determining the effect of acid and base additions during sludge carbonization. Based on the results carbonization was mainly governed by dehydration, depolymerization and decarboxylation of sludge components. Additive type had a statistically significant effect on hydrochar carbon content and carbon and energy yield, of which especially energy yield increased through the use of HCl. The theoretical energy efficiencies of carbonization increased with decreasing reaction temperature, retention time and the use of HCl and suggested that the energy requirement could be covered by the energy content of attained hydrochar. The BOD5/COD-ratios of analyzed liquid samples indicated that the dissolved organic components could be treated by conventional biological methods.

Original languageEnglish
Pages (from-to)444-450
Number of pages7
JournalBioresource Technology
Publication statusPublished - 1 Jan 2016
MoE publication typeA1 Journal article-refereed


  • Biosolids
  • Hydrothermal treatment
  • Sludge treatment
  • Waste biomass
  • Wet torrefaction


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