Insights into the roles of humic acids in facilitating the anaerobic digestion process

Rong Zhu; Miao Yan; Yun Zhang; Hua Zou; Yi Zheng; Rongbo Guo; Shanfei Fu

doi:10.1016/j.wasman.2023.05.050

Insights into the roles of humic acids in facilitating the anaerobic digestion process

Waste Manag. 2023 Aug 1:168:25-34. doi: 10.1016/j.wasman.2023.05.050. Epub 2023 Jun 3.

Authors

Rong Zhu¹, Miao Yan², Yun Zhang³, Hua Zou⁴, Yi Zheng⁵, Rongbo Guo⁶, Shanfei Fu⁷

Affiliations

¹ Jiangxi Provincial Key Laboratory of Low-Carbon Solid Waste Recycling, School of Geography and Environmental Engineering, Gannan Normal University, Ganzhou, 34100, PR China; Jiangsu Key Laboratory of Anaerobic Biotechnology, School of Environment and Civil Engineering, Jiangnan University, Wuxi, Jiangsu Province 214122, PR China. Electronic address: 1400070@gnnu.edu.cn.
² Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou, 510640, PR China. Electronic address: yanmiao@ms.giec.ac.cn.
³ Jiangsu Key Laboratory of Anaerobic Biotechnology, School of Environment and Civil Engineering, Jiangnan University, Wuxi, Jiangsu Province 214122, PR China. Electronic address: zhangyun@jiangnan.edu.cn.
⁴ Jiangsu Key Laboratory of Anaerobic Biotechnology, School of Environment and Civil Engineering, Jiangnan University, Wuxi, Jiangsu Province 214122, PR China. Electronic address: zouhua@jiangnan.edu.cn.
⁵ Department of Grain Science and Industry, Kansas State University, Manhattan, KS 66506, United States. Electronic address: yzheng@ksu.edu.
⁶ Shandong Industrial Engineering Laboratory of Biogas Production & Utilization, Key Laboratory of Biofuels, Shandong Provincial Key Laboratory of Synthetic Biology, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, NO. 189 Songling Road, Qingdao 266101, PR China. Electronic address: guorb@qibebt.ac.cn.
⁷ Shandong Industrial Engineering Laboratory of Biogas Production & Utilization, Key Laboratory of Biofuels, Shandong Provincial Key Laboratory of Synthetic Biology, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, NO. 189 Songling Road, Qingdao 266101, PR China; State Key Laboratory of Pollution Control and Resource Reuse, Nanjing 210023, PR China. Electronic address: fusf@qibebt.ac.cn.

PMID: 37276631
DOI: 10.1016/j.wasman.2023.05.050

Abstract

Humic acids (HAs) are important byproducts of anaerobic digestion (AD), which have complex structures and dynamic electrochemical activities. However, the effects of HAs on AD process were usually misestimated due to the neglect of the in situ generated HAs and the interaction between HAs and metal ions. This study explored the effects of HAs on AD performance using corn straw as typical "clean" substrate (rare in metals content) via commercial HAs (C-HAs) addition and in-situ-generated HAs (In-HAs) removal. Results showed that C-HAs (1 g/L) addition promoted the maximum methane production rate (R_m) by 20.6%, while In-HAs removal decreased the R_m by 42.7%. Meanwhile, C-HAs showed little effect on the acidification of corn straw but increased the R_m during the methanation of ethanol by 41.6%. Both the C-HAs and In-HAs were rich in surface oxygen-containing functional groups, which enabled them to act as electron shuttles and facilitate the syntrophic methanogenesis. HAs also acted in regulation of syntrophic microorganisms. For instance, C-HAs addition enriched the relative abundances of Cloacimonadia, Spirochaetia, Synergistia and Methanosarcina, while the removal of In-HAs reduced the relative abundances of Spirochaetia and Synergistia. In conclusion, HAs addition to the AD process could be a feasible approach to improve methane production by enhancing direct interspecies electron transfer during AD of lignocellulosic biomass.

Keywords: Anaerobic digestion; Direct interspecies transfer; Humic acids; Lignocellulosic biomass; Microbial community.

MeSH terms

Anaerobiosis
Bioreactors
Humic Substances*
Methane*
Methanosarcina

Substances

Humic Substances
Methane