Simultaneous enhancement on lignocellulose degradation and humic acid formation using the electric field coupled with an iron anode in the co-composting of food waste and agricultural waste

Abstract

The co-composting of food waste and agricultural waste presents a promising biotechnology for mitigating the challenges of organic solid waste treatment. However, the low degradation rate of lignocellulosic content hindered its application. This study explored a novel approach that employs an electric field coupled with an Fe anode to accelerate crude fiber decomposition and humic acid formation in a composting system. The results demonstrated that the group subjected to direct current exposure matched Fe anode (EF) exhibited the lowest crude fiber content, supported by observed loose cellulose structures using a confocal laser scanning microscope. The humic acid content in EF was also superior, exceeding both the control group without direct current exposure (CK) and with direct current exposure matched carbon anode (EA) by 72.5% and 29.3%, respectively. Two-dimensional FTIR correlation spectroscopy analysis revealed that this technology leveraged the intermediate products of lignocellulose degradation to provide a stable core structure for humic acid formation, promoting the highest humification degree. Microbial community analysis indicated that the enriched dominant phylum Firmicutes in EF was responsible for crude fiber degradation. Metagenomics analysis further suggested that the upregulations of carbohydrate-active enzymes with the signal peptide and reactive oxygen species formation triggered by microorganisms contributed to the crude fiber decomposition. This study demonstrates an efficient technology for improving composting quality.