Document Type


Publication Date




Publication Title

Organic Geochemistry




104637 (1-14)


In efforts to produce a higher quality algal derived biofuel, a two-step hydrothermal liquefaction (HTL) treatment is employed. This two-step process aims to reduce nitrogen and oxygen content in the first step using a low temperature treatment, termed hydrothermal hydrolysis (HTH), to solubilize proteins and carbohydrates while concentrating the energy rich biopolymer algaenan. In the second step, the solid residue is separated from the aqueous fraction and subjected to a higher HTL temperature for a longer residence time to crack the algaenan biopolymer into oil. Two different residence time and temperature conditions (260 °C for 0.5 h and 200 °C for 24 h) were found to effectively reduce the N and O content from 10.1 ± 0.3 wt. %N and 30.5 ± 0.7 wt. %O in the starting algae to 3.2 ± 0.2 wt. %N and 17.2 ± 1.1 wt. %O at 260 °C for 0.5 h and to 4.5 ± 0.1 wt. %N and 17.1 ± 0.7 wt. %O at 200 °C for 24 h. These residues were treated at 360 °C for 72 h during the second step HTL treatment. Following the second step treatment, the oil fraction is collected and analyzed using advanced analytical techniques that show the oil is similar in molecular composition to a Type I crude oil and has a reduced heteroatom content (1.3 ± 0.0 wt. %N and 5.7 ± 0.8 wt. %O) when compared to oil generated through a single step HTL (3.5 wt. %N and 16.3 wt. %O).


This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

© 2023 Elsevier. This manuscript version is made available after an embargo period of 24 months under the CC-BY-NC-ND 4.0 license

Data Availability

Article states: Data will be made available on request.

Original Publication Citation

Bondurant, L. C., Obeid, W., & Hatcher, P. G. (2023). Two-step hydrothermal liquefaction of Scenedesmus/Desmodesmus algae for the production of hydrocarbon-based fuels. Organic Geochemistry, 182, 1-14, Article 104637.


0000-0002-5970-8260 (Bondurant), 0000-0002-6054-411X (Obeid),0000-0002-1606-1305 (Hatcher)

Available for download on Friday, August 01, 2025