Co-processing of Hydrothermal Liquefaction Sewage Sludge Biocrude with a Fossil Crude Oil by Codistillation: A Detailed Characterization Study by FTICR Mass Spectrometry

Stefano Chiaberge*, Andrea Siviero, Cinzia Passerini, Silvia Pavoni, Daniele Bianchi, Muhammad Salman Haider, Daniele Castello

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

7 Citations (Scopus)


Co-processing renewable feedstock in existing refineries could be a prompt and ready-to-use approach to decarbonize the transportation sector, without large modifications to current processing infrastructures. In this study, we explore the possibility of codistilling a blend of fossil crude with hydrothermal liquefaction (HTL) biocrude from primary sewage sludge. HTL biocrude is indeed gaining an increasingly relevant role, because it can be produced from a huge variety of biomass feedstock, including wet byproducts, with no competition with food or feed applications. Despite the highly valuable properties of HTL in comparison with other bio-oils (high heating value, relatively low heteroatoms content, etc.), its introduction in a refinery distillation unit can still be problematic, because of its high acidity and inorganics content. Therefore, partial hydrotreatment was performed prior to blending with a low-sulfur fossil oil, which allowed a blending ratio of 1:4. Codistillation tests were compared with an analogous test with pure fossil oil, in order to assess the contribution of the biomass feed. The obtained distilled cuts were fully analyzed, and a petroleomic approach employing FTICR mass spectrometry was used for a more-detailed characterization at the molecular level. Results showed that biocrude mostly contributes to the high boiling point fractions, especially diesel and residue, although a significant contribution can be also observed to the kerosene range. However, significant amounts of nitrogen were found in the distilled fractions, corresponding to compounds recalcitrant to hydrotreating, resulting in a different carbon number and double-bond equivalent (DBE) distribution. This issue could be controlled by reducing the blending ratio or with specific upgrading treatments. Therefore, codistillation of HTL biocrude with fossil oil is a promising route for the introduction of renewables in the existing refineries.
Original languageEnglish
JournalEnergy and Fuels
Issue number17
Pages (from-to)13830-13839
Number of pages10
Publication statusPublished - 2 Sep 2021

Bibliographical note

Funding Information:
This project has received funding from the European Union’s Horizon 2020 research and innovation programme, under Grant Agreement No. 764734 (HyFlexFuel). The authors would also like to thank J. S. Dos Passos and Patrick Biller (University of Aarhus, Denmark), for providing the Sewage Sludge HTL Bio-Crude.

Publisher Copyright:
© 2021 American Chemical Society


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