Humic acid-anchored hydrochar for enhancing methane production in anaerobic digestion of cow manure.

Journal: Journal of environmental management
Published Date: May 9, 2025

Abstract

This study assesses the effectiveness of two hydrochar variants-humic acid-anchored hydrochar and sodium hydroxide-modified hydrochar-in enhancing biogas production from high-solids anaerobic digestion of cow manure. The purpose of humic acid modification is that its abundant oxygen-containing functional groups promote direct interspecies electron transfer and improve microbial efficiency in anaerobic digestion. Humic acid-anchored hydrochar was prepared by anchoring humic acid to hydrochar. To further optimize the electron transfer capacity and structural properties of the hydrochar, the humic acid-anchored hydrochar was subsequently treated with sodium hydroxide to produce sodium hydroxide-modified hydrochar. The alkali modification effectively removes pore impurities and enhances the redox properties of the material, thereby improving the electron exchange between microorganisms. Experiments were conducted in 500 mL anaerobic serum bottles at a total solids content of 10 %. In the control group, high ammonia nitrogen concentrations inhibited methane production, yielding only 49.54 mL/g volatile solids. In contrast, the addition of sodium hydroxide-modified hydrochar increased cumulative methane production by 80.13 %, reaching 112.38 mL/g VS. Additionally, electron transfer system activity and coenzyme F levels increased 94.13 % and 96.58 %, respectively. Microbial analysis revealed an enrichment of bacteria involved in direct interspecies electron transfer and an optimized community structure. Correlation analysis demonstrated a significant positive relationship between enhanced interspecies electron transfer capacity and methane production. The incorporation of modified hydrochar enabled the anaerobic digestion system to maintain high methane yields despite elevated ammonia nitrogen levels. These findings offer valuable insights for improving livestock and poultry manure management and advancing environmental protection efforts.

Authors

  • Aiyong He
    Jiangsu Key Laboratory for Biomass-Based Energy and Enzyme Technology, Huaiyin Normal University, Huaian 223300, PR China.
  • Yang Liu
    Department of Computer Science, Hong Kong Baptist University, Hong Kong, China.
  • Chunhui Cao
    The Key Laboratory of Crop and Livestock Integration of the Ministry of Agriculture and Rural Affairs, Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, Jiangsu Academy of Agriculture Sciences, Nanjing, 210014, China.
  • Qingbo Xiao
    The Key Laboratory of Crop and Livestock Integration of the Ministry of Agriculture and Rural Affairs, Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, Jiangsu Academy of Agriculture Sciences, Nanjing, 210014, China.
  • Jiaxing Xu
    Jiangsu Key Laboratory for Biomass-based Energy and Enzyme Technology, Jiangsu Collaborative Innovation Center of Regional Modern Agriculture & Environmental Protection, School of Chemistry and Chemical Engineering, Huaiyin Normal University, Huai'an, 223300, China.
  • Yanfang Feng
    The Key Laboratory of Crop and Livestock Integration of the Ministry of Agriculture and Rural Affairs, Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, Jiangsu Academy of Agriculture Sciences, Nanjing, 210014, China.
  • Zhiyang Zhang
    Acupuncture and Tuina School, Chengdu University of Traditional Chinese Medicine, Chengdu, Sichuan, China.
  • Yonglan Xi
    The Key Laboratory of Crop and Livestock Integration of the Ministry of Agriculture and Rural Affairs, Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, Jiangsu Academy of Agriculture Sciences, Nanjing, 210014, China. Electronic address: yonglanxi@jaas.ac.cn.

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