IDEAS home Printed from https://ideas.repec.org/a/gam/jeners/v18y2025i8p2094-d1637442.html
   My bibliography  Save this article

Hydrothermal Liquefaction for Biofuel Synthesis: Assessment of VFA (Volatile Fatty Acid) and FAME (Fatty Acid Methyl Ester) Profiles from Spent Coffee Grounds

Author

Listed:
  • Dimitrios Liakos

    (Energy Management Laboratory, Department of Environment, University of the Aegean, University Hill, 81100 Mytilene, Greece)

  • Georgia Altiparmaki

    (Energy Management Laboratory, Department of Environment, University of the Aegean, University Hill, 81100 Mytilene, Greece)

  • Simos Malamis

    (Laboratory of Sanitary Engineering, School of Civil Engineering, National Technical University of Athens, Zographou Campus, 15780 Athens, Greece)

  • Stergios Vakalis

    (Energy Management Laboratory, Department of Environment, University of the Aegean, University Hill, 81100 Mytilene, Greece
    School of Chemical Engineering, National Technical University of Athens, 15780 Athens, Greece)

Abstract

Spent coffee grounds (SCGs) are an underutilized biomass resource with high potential for renewable energy and bioproduct synthesis. This study applies hydrothermal liquefaction to transform SCGs into high-quality biofuels and value-added biochemicals. Five experiments were conducted over a temperature range of 300 °C to 380 °C, highlighting significant temperature-dependent shifts in product composition. Notably, phenolic compounds peaked at 1180.1 mg/L at 300 °C before declining sharply, while chemical oxygen demand (COD) dropped to a minimum of 13,949.8 mg/L at 350 °C—a temperature that also maximized hydrochar yield (26%) and achieved a high heating value of 32.9 MJ/kg. Plasma chromatographic analyses showed the dynamic behavior of volatile fatty acids (VFAs) and fatty acid methyl esters (FAMEs); maximum levels of acetic (540.7 mg/L), formic (67.8 mg/L), and propionic acids (155.6 mg/L) were recorded at 300 °C, whereas FAMEs such as methyl butyrate, methyl hexanoate, methyl undecanoate, and methyl palmitate increased markedly at higher temperatures due to intensified carboxylation reactions. These results denote the potential of hydrothermal liquefaction to valorize SCGs for the production of biomolecules, expanding the conventional sustainable biofuel production pathways.

Suggested Citation

  • Dimitrios Liakos & Georgia Altiparmaki & Simos Malamis & Stergios Vakalis, 2025. "Hydrothermal Liquefaction for Biofuel Synthesis: Assessment of VFA (Volatile Fatty Acid) and FAME (Fatty Acid Methyl Ester) Profiles from Spent Coffee Grounds," Energies, MDPI, vol. 18(8), pages 1-14, April.
    • Handle: RePEc:gam:jeners:v:18:y:2025:i:8:p:2094-:d:1637442
    as

    Download full text from publisher

    File URL: https://www.mdpi.com/1996-1073/18/8/2094/pdf
    Download Restriction: no
    File URL: https://www.mdpi.com/1996-1073/18/8/2094/
    Download Restriction: no
    ---><---

    References listed on IDEAS

    as
    1. Liu, Huan & Basar, Ibrahim Alper & Eskicioglu, Cigdem, 2023. "Hydrothermal liquefaction for sludge-to-energy conversion: An evaluation of biocrude production and management of waste streams," Energy, Elsevier, vol. 281(C).
    2. Joshua O. Ighalo & Florence C. Akaeme & Jordana Georgin & Jivago Schumacher de Oliveira & Dison S. P. Franco, 2025. "Biomass Hydrochar: A Critical Review of Process Chemistry, Synthesis Methodology, and Applications," Sustainability, MDPI, vol. 17(4), pages 1-44, February.
    3. Afolabi, Oluwasola O.D. & Sohail, M. & Cheng, Yu-Ling, 2020. "Optimisation and characterisation of hydrochar production from spent coffee grounds by hydrothermal carbonisation," Renewable Energy, Elsevier, vol. 147(P1), pages 1380-1391.
    4. Kang, Sae Byul & Oh, Hong Young & Kim, Jong Jin & Choi, Kyu Sung, 2017. "Characteristics of spent coffee ground as a fuel and combustion test in a small boiler (6.5 kW)," Renewable Energy, Elsevier, vol. 113(C), pages 1208-1214.
    5. Md Tahmid Islam & Al Ibtida Sultana & Cadianne Chambers & Swarna Saha & Nepu Saha & Kawnish Kirtania & M. Toufiq Reza, 2022. "Recent Progress on Emerging Applications of Hydrochar," Energies, MDPI, vol. 15(24), pages 1-45, December.
    6. Yulin Hu & Rhea Gallant & Shakirudeen Salaudeen & Aitazaz A. Farooque & Sophia He, 2022. "Hydrothermal Carbonization of Spent Coffee Grounds for Producing Solid Fuel," Sustainability, MDPI, vol. 14(14), pages 1-15, July.
    Full references (including those not matched with items on IDEAS)

    Most related items

    These are the items that most often cite the same works as this one and are cited by the same works as this one.
    1. Marcin Sajdak & Roksana Muzyka & Grzegorz Gałko & Ewelina Ksepko & Monika Zajemska & Szymon Sobek & Dariusz Tercki, 2022. "Actual Trends in the Usability of Biochar as a High-Value Product of Biomass Obtained through Pyrolysis," Energies, MDPI, vol. 16(1), pages 1-30, December.
    2. Diana L. Tinoco Caicedo & Myrian Santos Torres & Medelyne Mero-Benavides & Oscar Patiño Lopez & Alexis Lozano Medina & Ana M. Blanco Marigorta, 2023. "Simulation and Exergoeconomic Analysis of a Trigeneration System Based on Biofuels from Spent Coffee Grounds," Energies, MDPI, vol. 16(4), pages 1-17, February.
    3. Śliz, Maciej & Wilk, Małgorzata, 2020. "A comprehensive investigation of hydrothermal carbonization: Energy potential of hydrochar derived from Virginia mallow," Renewable Energy, Elsevier, vol. 156(C), pages 942-950.
    4. Klüpfel, Christian & Yuan, Bomin & Biller, Patrick & Herklotz, Benjamin, 2025. "Hydrothermal liquefaction as a treatment technology for anaerobic digestate: A review," Renewable and Sustainable Energy Reviews, Elsevier, vol. 210(C).
    5. Marco Balsamo & Francesca Di Lauro & Maria Laura Alfieri & Paola Manini & Piero Salatino & Fabio Montagnaro & Roberto Solimene, 2024. "Unravelling the Role of Biochemical Compounds within the Hydrothermal Liquefaction Process of Real Sludge Mixtures," Sustainability, MDPI, vol. 16(5), pages 1-18, February.
    6. Chen, Ying-Chu & Jhou, Sih-Yu, 2020. "Integrating spent coffee grounds and silver skin as biofuels using torrefaction," Renewable Energy, Elsevier, vol. 148(C), pages 275-283.
    7. Djandja, Oraléou Sangué & Duan, Pei-Gao & Yin, Lin-Xin & Wang, Zhi-Cong & Duo, Jia, 2021. "A novel machine learning-based approach for prediction of nitrogen content in hydrochar from hydrothermal carbonization of sewage sludge," Energy, Elsevier, vol. 232(C).
    8. Lachman, Jakub & Lisý, Martin & Baláš, Marek & Matúš, Miloš & Lisá, Hana & Milčák, Pavel, 2022. "Spent coffee grounds and wood co-firing: Fuel preparation, properties, thermal decomposition, and emissions," Renewable Energy, Elsevier, vol. 193(C), pages 464-474.
    9. Chang, Boon Peng & Rodriguez-Uribe, Arturo & Mohanty, Amar K. & Misra, Manjusri, 2021. "A comprehensive review of renewable and sustainable biosourced carbon through pyrolysis in biocomposites uses: Current development and future opportunity," Renewable and Sustainable Energy Reviews, Elsevier, vol. 152(C).
    10. Xie, Rui & Chen, Zhengjie & Ma, Wenhui & Wang, Xiaoyue & Gan, Xiaowei & Tao, Chenggang & Qu, Junyu, 2024. "High efficient and clean utilization of renewable energy for the process of industrial silicon," Renewable Energy, Elsevier, vol. 231(C).
    11. Mátyás Köves & Viktor Madár & Marianna Ringer & Tamás Kocsis, 2024. "Overview of Traditional and Contemporary Industrial Production Technologies for Biochar along with Quality Standardization Methods," Land, MDPI, vol. 13(9), pages 1-12, August.
    12. Zhu, Zhe & Sun, Zhiqiang & Yu, Xiaofeng & Zhang, Shuo & Cao, Xinxin & Liu, Xuliang & Guo, Ziwen & Rosendahl, Lasse & Chen, Guanyi, 2024. "Valorization of low heavy metal-accumulating plants through catalytic hydrothermal liquefaction with attapulgite: Product characterization and migration behavior of heavy metals," Energy, Elsevier, vol. 295(C).
    13. Magdalena Dołżyńska & Sławomir Obidziński & Małgorzata Kowczyk-Sadowy & Małgorzata Krasowska, 2019. "Densification and Combustion of Cherry Stones," Energies, MDPI, vol. 12(16), pages 1-15, August.
    14. Hao Chen & Fangfang Lou & Xueyi Zhang & Chengjun Shen & Weicheng Pan & Shuang Wang, 2023. "Hydrothermal Conversion of Microalgae Slurry in a Continuous Solar Collector with Static Mixer for Heat Transfer Enhancement," Energies, MDPI, vol. 16(24), pages 1-16, December.
    15. Radovan Nosek & Maw Maw Tun & Dagmar Juchelkova, 2020. "Energy Utilization of Spent Coffee Grounds in the Form of Pellets," Energies, MDPI, vol. 13(5), pages 1-8, March.
    16. Sooraj Kumar & Suhail Ahmed Soomro & Khanji Harijan & Mohammad Aslam Uqaili & Laveet Kumar, 2023. "Advancements of Biochar-Based Catalyst for Improved Production of Biodiesel: A Comprehensive Review," Energies, MDPI, vol. 16(2), pages 1-20, January.
    17. Jiseok Hong & Changwon Chae & Hyunjoong Kim & Hyeokjun Kwon & Jisu Kim & Ijung Kim, 2023. "Investigation to Enhance Solid Fuel Quality in Torrefaction of Cow Manure," Energies, MDPI, vol. 16(11), pages 1-13, June.
    18. Pietro Romano & Nicola Stampone & Gabriele Di Giacomo, 2023. "Evolution and Prospects of Hydrothermal Carbonization," Energies, MDPI, vol. 16(7), pages 1-11, March.
    19. Leslie Lara-Ramos & Ana Cervera-Mata & Jesús Fernández-Bayo & Miguel Navarro-Alarcón & Gabriel Delgado & Alejandro Fernández-Arteaga, 2023. "Hydrochars Derived from Spent Coffee Grounds as Zn Bio-Chelates for Agronomic Biofortification," Sustainability, MDPI, vol. 15(13), pages 1-13, July.
    20. Rhea Gallant & Aitazaz A. Farooque & Sophia He & Kang Kang & Yulin Hu, 2022. "A Mini-Review: Biowaste-Derived Fuel Pellet by Hydrothermal Carbonization Followed by Pelletizing," Sustainability, MDPI, vol. 14(19), pages 1-18, October.

    More about this item

    Keywords

    ;
    ;
    ;
    ;

    Statistics

    Access and download statistics

    Corrections

    All material on this site has been provided by the respective publishers and authors. You can help correct errors and omissions. When requesting a correction, please mention this item's handle: RePEc:gam:jeners:v:18:y:2025:i:8:p:2094-:d:1637442. See general information about how to correct material in RePEc.

    If you have authored this item and are not yet registered with RePEc, we encourage you to do it here. This allows to link your profile to this item. It also allows you to accept potential citations to this item that we are uncertain about.

    If CitEc recognized a bibliographic reference but did not link an item in RePEc to it, you can help with this form .

    If you know of missing items citing this one, you can help us creating those links by adding the relevant references in the same way as above, for each refering item. If you are a registered author of this item, you may also want to check the "citations" tab in your RePEc Author Service profile, as there may be some citations waiting for confirmation.

    For technical questions regarding this item, or to correct its authors, title, abstract, bibliographic or download information, contact: MDPI Indexing Manager (email available below). General contact details of provider: https://www.mdpi.com .

    Please note that corrections may take a couple of weeks to filter through the various RePEc services.

    IDEAS is a RePEc service. RePEc uses bibliographic data supplied by the respective publishers.