IDEAS home Printed from https://ideas.repec.org/a/gam/jsusta/v17y2025i4p1660-d1592924.html
   My bibliography  Save this article

Biomass Hydrochar: A Critical Review of Process Chemistry, Synthesis Methodology, and Applications

Author

Listed:
  • Joshua O. Ighalo

    (Department of Chemical Engineering, Nnamdi Azikiwe University, P. M. B. 5025, Awka 420110, Nigeria
    Tim Taylor Department of Chemical Engineering, Kansas State University, Manhattan, KS 66506, USA)

  • Florence C. Akaeme

    (Department of Chemical Engineering, Nnamdi Azikiwe University, P. M. B. 5025, Awka 420110, Nigeria)

  • Jordana Georgin

    (Department of Civil and Environmental, Universidad de La Costa, CUC, Calle 58 # 55–66, Barranquilla 50366, Colombia)

  • Jivago Schumacher de Oliveira

    (Applied Nanomaterials Research Group (GPNAp), Nanoscience Graduate Program, Franciscan University (UFN), Santa Maria 97010-032, RS, Brazil
    Postgraduate Program, Nanoscience Franciscan University (UFN), Santa Maria 97010-032, RS, Brazil)

  • Dison S. P. Franco

    (Department of Civil and Environmental, Universidad de La Costa, CUC, Calle 58 # 55–66, Barranquilla 50366, Colombia
    Applied Nanomaterials Research Group (GPNAp), Nanoscience Graduate Program, Franciscan University (UFN), Santa Maria 97010-032, RS, Brazil)

Abstract

Hydrothermal carbonization (HTC) is a novel thermochemical process that turns biomass into hydrochar, a substance rich in carbon that has potential uses in advanced material synthesis, energy production, and environmental remediation. With an emphasis on important chemical pathways, such as dehydration, decarboxylation, and polymerization, that control the conversion of lignocellulosic biomass into useful hydrochar, this review critically investigates the fundamental chemistry of HTC. A detailed analysis is conducted on the effects of process variables on the physicochemical characteristics of hydrochar, including temperature, pressure, biomass composition, water ratio, and residence time. Particular focus is placed on new developments in HTC technology that improve sustainability and efficiency, like recirculating process water and microwave-assisted co-hydrothermal carbonization. Furthermore, the improvement of adsorption capacity for organic contaminants and heavy metals is explored in relation to the functionalization and chemical activation of hydrochar, namely through surface modification and KOH treatment. The performance of hydrochar and biochar in adsorption, catalysis, and energy storage is compared, emphasizing the unique benefits and difficulties of each substance. Although hydrochar has a comparatively high higher heating value (HHV) and can be a good substitute for coal, issues with reactor design, process scalability, and secondary waste management continue to limit its widespread use. In order to maximize HTC as a sustainable and profitable avenue for biomass valorization, this study addresses critical research gaps and future initiatives.

Suggested Citation

  • 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.
    • Handle: RePEc:gam:jsusta:v:17:y:2025:i:4:p:1660-:d:1592924
    as

    Download full text from publisher

    File URL: https://www.mdpi.com/2071-1050/17/4/1660/pdf
    Download Restriction: no
    File URL: https://www.mdpi.com/2071-1050/17/4/1660/
    Download Restriction: no
    ---><---

    References listed on IDEAS

    as
    1. Salaudeen, Shakirudeen A. & Acharya, Bishnu & Dutta, Animesh, 2021. "Steam gasification of hydrochar derived from hydrothermal carbonization of fruit wastes," Renewable Energy, Elsevier, vol. 171(C), pages 582-591.
    2. Gomez, Arturo & Silbermann, Rico & Mahinpey, Nader, 2014. "A comprehensive experimental procedure for CO2 coal gasification: Is there really a maximum reaction rate?," Applied Energy, Elsevier, vol. 124(C), pages 73-81.
    3. Gai, Chao & Chen, Mengjun & Liu, Tingting & Peng, Nana & Liu, Zhengang, 2016. "Gasification characteristics of hydrochar and pyrochar derived from sewage sludge," Energy, Elsevier, vol. 113(C), pages 957-965.
    4. Lai, Fa-ying & Chang, Yan-chao & Huang, Hua-jun & Wu, Guo-qiang & Xiong, Jiang-bo & Pan, Zi-qian & Zhou, Chun-fei, 2018. "Liquefaction of sewage sludge in ethanol-water mixed solvents for bio-oil and biochar products," Energy, Elsevier, vol. 148(C), pages 629-641.
    5. Li, Jie & Pan, Lanjia & Suvarna, Manu & Tong, Yen Wah & Wang, Xiaonan, 2020. "Fuel properties of hydrochar and pyrochar: Prediction and exploration with machine learning," Applied Energy, Elsevier, vol. 269(C).
    6. Masoumi, Shima & Boahene, Philip E. & Dalai, Ajay K., 2021. "Biocrude oil and hydrochar production and characterization obtained from hydrothermal liquefaction of microalgae in methanol-water system," Energy, Elsevier, vol. 217(C).
    7. Shen, Yafei & Yu, Shili & Ge, Shun & Chen, Xingming & Ge, Xinlei & Chen, Mindong, 2017. "Hydrothermal carbonization of medical wastes and lignocellulosic biomass for solid fuel production from lab-scale to pilot-scale," Energy, Elsevier, vol. 118(C), pages 312-323.
    8. Shao, Yuchao & Long, Yuyang & Wang, Hengyi & Liu, Dongyun & Shen, Dongsheng & Chen, Ting, 2019. "Hydrochar derived from green waste by microwave hydrothermal carbonization," Renewable Energy, Elsevier, vol. 135(C), pages 1327-1334.
    9. Galindo, José & Climent, Héctor & de la Morena, Joaquín & González-Domínguez, David & Guilain, Stéphane, 2023. "Assessment of air management strategies to improve the transient response of advanced gasoline engines operating under high EGR conditions," Energy, Elsevier, vol. 262(PB).
    10. Lech Nowicki & Dorota Siuta & Maciej Markowski, 2020. "Carbon Dioxide Gasification Kinetics of Char from Rapeseed Oil Press Cake," Energies, MDPI, vol. 13(9), pages 1-12, May.
    11. Munir, M. Tajammal & Mansouri, Seyed Soheil & Udugama, Isuru A. & Baroutian, Saeid & Gernaey, Krist V. & Young, Brent R., 2018. "Resource recovery from organic solid waste using hydrothermal processing: Opportunities and challenges," Renewable and Sustainable Energy Reviews, Elsevier, vol. 96(C), pages 64-75.
    12. He, Chao & Giannis, Apostolos & Wang, Jing-Yuan, 2013. "Conversion of sewage sludge to clean solid fuel using hydrothermal carbonization: Hydrochar fuel characteristics and combustion behavior," Applied Energy, Elsevier, vol. 111(C), pages 257-266.
    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. Wądrzyk, Mariusz & Korzeniowski, Łukasz & Plata, Marek & Janus, Rafał & Lewandowski, Marek & Michalik, Marek & Magdziarz, Aneta, 2023. "Pyrolysis of hydrochars obtained from blackcurrant pomace in single and binary solvent systems," Renewable Energy, Elsevier, vol. 214(C), pages 383-394.
    2. Pablo J. Arauzo & María Atienza-Martínez & Javier Ábrego & Maciej P. Olszewski & Zebin Cao & Andrea Kruse, 2020. "Combustion Characteristics of Hydrochar and Pyrochar Derived from Digested Sewage Sludge," Energies, MDPI, vol. 13(16), pages 1-15, August.
    3. Ma, Jing & Chen, Mengjun & Yang, Tianxue & Liu, Zhengang & Jiao, Wentao & Li, Dong & Gai, Chao, 2019. "Gasification performance of the hydrochar derived from co-hydrothermal carbonization of sewage sludge and sawdust," Energy, Elsevier, vol. 173(C), pages 732-739.
    4. Zhuang, Xiuzheng & Liu, Jianguo & Zhang, Qi & Wang, Chenguang & Zhan, Hao & Ma, Longlong, 2022. "A review on the utilization of industrial biowaste via hydrothermal carbonization," Renewable and Sustainable Energy Reviews, Elsevier, vol. 154(C).
    5. Zhang, Deli & Wang, Fang & Shen, Xiuli & Yi, Weiming & Li, Zhihe & Li, Yongjun & Tian, Chunyan, 2018. "Comparison study on fuel properties of hydrochars produced from corn stalk and corn stalk digestate," Energy, Elsevier, vol. 165(PB), pages 527-536.
    6. Gallifuoco, Alberto & Taglieri, Luca & Papa, Alessandro Antonio, 2020. "Hydrothermal carbonization of waste biomass to fuel: A novel technique for analyzing experimental data," Renewable Energy, Elsevier, vol. 149(C), pages 1254-1260.
    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. Parandin, M.S. & Ale Ebrahim, H. & Norouzi, H.R., 2024. "Towards random pore model for non-catalytic gas-solid reactions," Renewable and Sustainable Energy Reviews, Elsevier, vol. 202(C).
    9. Azzaz, Ahmed Amine & Khiari, Besma & Jellali, Salah & Ghimbeu, Camélia Matei & Jeguirim, Mejdi, 2020. "Hydrochars production, characterization and application for wastewater treatment: A review," Renewable and Sustainable Energy Reviews, Elsevier, vol. 127(C).
    10. He, Chao & Tang, Chunyan & Li, Chuanhao & Yuan, Jihui & Tran, Khanh-Quang & Bach, Quang-Vu & Qiu, Rongliang & Yang, Yanhui, 2018. "Wet torrefaction of biomass for high quality solid fuel production: A review," Renewable and Sustainable Energy Reviews, Elsevier, vol. 91(C), pages 259-271.
    11. Chen, Congjin & Zhu, Jingxian & Jia, Shuang & Mi, Shuai & Tong, Zhangfa & Li, Zhixia & Li, Mingfei & Zhang, Yanjuan & Hu, Yuhua & Huang, Zuqiang, 2018. "Effect of ethanol on Mulberry bark hydrothermal liquefaction and bio-oil chemical compositions," Energy, Elsevier, vol. 162(C), pages 460-475.
    12. Kumar, Mayank & Olajire Oyedun, Adetoyese & Kumar, Amit, 2018. "A review on the current status of various hydrothermal technologies on biomass feedstock," Renewable and Sustainable Energy Reviews, Elsevier, vol. 81(P2), pages 1742-1770.
    13. Shahbeik, Hossein & Kazemi Shariat Panahi, Hamed & Dehhaghi, Mona & Guillemin, Gilles J. & Fallahi, Alireza & Hosseinzadeh-Bandbafha, Homa & Amiri, Hamid & Rehan, Mohammad & Raikwar, Deepak & Latine, , 2024. "Biomass to biofuels using hydrothermal liquefaction: A comprehensive review," Renewable and Sustainable Energy Reviews, Elsevier, vol. 189(PB).
    14. Yao, Zhongliang & Ma, Xiaoqian, 2017. "A new approach to transforming PVC waste into energy via combined hydrothermal carbonization and fast pyrolysis," Energy, Elsevier, vol. 141(C), pages 1156-1165.
    15. Leng, Lijian & Zhou, Junhui & Zhang, Weijin & Chen, Jiefeng & Wu, Zhibin & Xu, Donghai & Zhan, Hao & Yuan, Xingzhong & Xu, Zhengyong & Peng, Haoyi & Yang, Zequn & Li, Hailong, 2024. "Machine-learning-aided hydrochar production through hydrothermal carbonization of biomass by engineering operating parameters and/or biomass mixture recipes," Energy, Elsevier, vol. 288(C).
    16. Sang Yeop Lee & Se Won Park & Md Tanvir Alam & Yean Ouk Jeong & Yong-Chil Seo & Hang Seok Choi, 2020. "Studies on the Gasification Performance of Sludge Cake Pre-Treated by Hydrothermal Carbonization," Energies, MDPI, vol. 13(6), pages 1-15, March.
    17. Teimouri, Zahra & Abatzoglou, Nicolas & Dalai, Ajay K., 2024. "A novel machine learning framework for designing high-performance catalysts for production of clean liquid fuels through Fischer-Tropsch synthesis," Energy, Elsevier, vol. 289(C).
    18. Dana-Claudia Farcas-Flamaropol & Radu Iatan & Petru Cardei & Ion Durbaca & Elena Surdu & Nicoleta Sporea, 2024. "Dewatering of Sludge Through Vibratory Sieving," Sustainability, MDPI, vol. 17(1), pages 1-16, December.
    19. Xiao, Zhihua & Yuan, Xingzhong & Jiang, Longbo & Chen, Xiaohong & Li, Hui & Zeng, Guangming & Leng, Lijian & Wang, Hou & Huang, Huajun, 2015. "Energy recovery and secondary pollutant emission from the combustion of co-pelletized fuel from municipal sewage sludge and wood sawdust," Energy, Elsevier, vol. 91(C), pages 441-450.
    20. Al-Jabri, Hareb & Das, Probir & Khan, Shoyeb & AbdulQuadir, Mohammad & Thaher, Mehmoud Ibrahim & Hoekman, Kent & Hawari, Alaa H., 2022. "A comparison of bio-crude oil production from five marine microalgae – Using life cycle analysis," Energy, Elsevier, vol. 251(C).

    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:jsusta:v:17:y:2025:i:4:p:1660-:d:1592924. 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.