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Peer-reviewedCC BYBiochar

Valorization of biogas digestate through hydrothermal humification for nitrogen-enriched artificial humic acid production

  • Yanan Zhao1
  • Ziyun Liu1
  • Zonglu Yao1
  • Dan Wang1
  • Jinting Su1
  • Jihua Yang2
  • Lili Huo1
  • Jixiu Jia1
  • Hugang Li3
  • Lixin Zhao1
  1. 1Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences
  2. 2College of Agronomy and Biotechnology/Center of Biomass Engineering, China Agricultural University
  3. 3College of Environment and Ecology, Taiyuan University of Technology
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Abstract

Biogas digestate (BD), a nutrient-rich and low-cost carbon source, can be converted into artificial humic acid (AHA) through hydrothermal humification (HTH). However, the process is often constrained by low efficiency and inconsistent product quality. In this study, the effects of different reaction media, including biogas slurry (BS) and deionized water, on the properties of AHA derived from BD at various temperatures (180–260 °C) were investigated. The results showed that BS addition increased both AHA yield and nitrogen content, with a maximum AHA selectivity of 40.16% in the hydrochar at 220 °C. FT-ICR-MS, 3D-EEM, and solid-state 13C NMR analyses indicated that lignin in BD was the main precursor for aromatic AHA synthesis in the deionized water system. When BS was introduced into the HTH process, lignin depolymerization and nitrogen-involving Maillard reactions were likely enhanced, resulting in greater nitrogen incorporation into AHA, with a maximum of 26.02 mg N retained in AHA at 220 °C. This enhanced nitrogen retention was associated with the formation of reactive intermediates and subsequent incorporation of nitrogen into more stable heterocyclic structures. This study provides a sustainable pathway for the efficient conversion of biogas plant residues into nutrient- and humic-rich products with potential as soil amendments. Graphical Abstract

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Cite

BibTeXRIS
BibTeX
@article{zhao2026valorization,
  title = {{Valorization of biogas digestate through hydrothermal humification for nitrogen-enriched artificial humic acid production}},
  author = {Yanan Zhao and Ziyun Liu and Zonglu Yao and Dan Wang and Jinting Su and Jihua Yang and Lili Huo and Jixiu Jia and Hugang Li and Lixin Zhao},
  journal = {Biochar},
  year = {2026},
  month = oct,
  doi = {10.1007/s42773-026-00662-4},
  url = {https://doi.org/10.1007/s42773-026-00662-4},
  note = {CC BY},
}
RIS
TY  - JOUR
TI  - Valorization of biogas digestate through hydrothermal humification for nitrogen-enriched artificial humic acid production
AU  - Yanan Zhao
AU  - Ziyun Liu
AU  - Zonglu Yao
AU  - Dan Wang
AU  - Jinting Su
AU  - Jihua Yang
AU  - Lili Huo
AU  - Jixiu Jia
AU  - Hugang Li
AU  - Lixin Zhao
PY  - 2026
DA  - 2026/10/25
JO  - Biochar
DO  - 10.1007/s42773-026-00662-4
UR  - https://doi.org/10.1007/s42773-026-00662-4
AB  - Biogas digestate (BD), a nutrient-rich and low-cost carbon source, can be converted into artificial humic acid (AHA) through hydrothermal humification (HTH). However, the process is often constrained by low efficiency and inconsistent product quality. In this study, the effects of different reaction media, including biogas slurry (BS) and deionized water, on the properties of AHA derived from BD at various temperatures (180–260 °C) were investigated. The results showed that BS addition increased both AHA yield and nitrogen content, with a maximum AHA selectivity of 40.16% in the hydrochar at 220 °C. FT-ICR-MS, 3D-EEM, and solid-state 13C NMR analyses indicated that lignin in BD was the main precursor for aromatic AHA synthesis in the deionized water system. When BS was introduced into the HTH process, lignin depolymerization and nitrogen-involving Maillard reactions were likely enhanced, resulting in greater nitrogen incorporation into AHA, with a maximum of 26.02 mg N retained in AHA at 220 °C. This enhanced nitrogen retention was associated with the formation of reactive intermediates and subsequent incorporation of nitrogen into more stable heterocyclic structures. This study provides a sustainable pathway for the efficient conversion of biogas plant residues into nutrient- and humic-rich products with potential as soil amendments. Graphical Abstract
SN  - 2524-7867
SN  - 2524-7972
ER  -