Mechanisms of genuine humic acid evolution and its dynamic interaction with methane production in anaerobic digestion processes

Abstract

Humic acid (HA), a byproduct formed during the biological conversion of organic matter into biogas in the anaerobic digestion (AD) process, contains complex structures and redox functions. However, the evolution mechanism of HA and its interaction with CH4 production during the AD process have not been fully explored, particularly with respect to various substrates and temperature conditions. In this study, we investigated the evolutionary dynamics of the structure and function of genuine HA that naturally formed in the AD processes of chicken manure and corn stover under mesophilic (37 °C) and thermophilic (55 °C) conditions. The results demonstrated that the HA evolution mechanisms in AD of chicken manure and corn stover have different pathways. The AD of core stover showed higher degree of aromaticity (41.2-66.7% and 45.3-68.4% for mesophilic and thermophilic respectively) and humification index (1.5-4.2 and 2.8-4.5 for mesophilic and thermophilic respectively) than those (28.3-45.3% and 30.2-54.5% of aromaticity and 0.6-1.2 and 1.3-3.7 of humification index) in AD of chicken manure. The

The Combined Application of Urea and Fulvic Acid Solution Improved Maize Carbon and Nitrogen Metabolism

“…Effects of Urea-FA Solution Combined Application on Soil Available Nutrients, Maize Yield, and NUE Organic wastes include crop straws and livestock manure, which can be used as raw materials for aerobic degradation to produce biochemical humic substances. The structure of humic substance shifted over time, including a wide range functional groupssuch as carboxylic, phenolic and hydroxylic groups, during anaerobic process [42,43]. Fulvic acid (FA) is one of the dominant components of humus [44], Originated from plant residues, FA is a type of organic polymer, containing carboxyl, quinone, phenolic hydroxyl, amide, and other functional groups, in this study (Figure S1).…”

Investigating the Evolution of Structural Characteristics of Humic Acid Generated during the Continuous Anaerobic Digestion and Its Potential for Chromium Adsorption and Reduction

“…The HA components of digestates were determined via a fluorescence spectrophotometer (Aqualog, HORIBA) following the method described in [2]. Briefly, around 50 mL digestate sample from the continuous AD process was diluted 20 times with distilled water.…”

“…The Fluorescence excitation-emission matrix (EEM) spectroscopy combined with PARAFAC analysis is often used to monitor the characteristics of organic matters [2,6,26]. The composition and evolution of the HA components were analyzed by EEM-PARAFAC analysis in this study.…”

“…For instance, the su ficial labile aliphatics of HA were first degraded as the energy source for microorganis growth due to insufficient substrate in batch AD process. Likewise, the exposed arom structures in HA were further degraded because of the low persistence of original arom ics, resulting in the decreased HA content during the first stage of the AD process However, with prolonged digestion, aliphatics and original aromatics degraded com nents (e.g., polyphenols and carboxylic acids) formed more unsaturated and stable via the re-polymerization process, resulting in increased HA content [2]. However, Li al.…”

“…Anaerobic digestion (AD) is widely used as an economical, effective, and environmentally friendly way of disposing of organic waste [1,2]. During the AD process, organic waste is degraded and converted into various soluble macromolecules and followed by the production of biogas via the hydrolysis, acidogenesis and methanogenesis processes [3,4].…”