Enhanced electron transfer capacity in lignin-rich compost-derived dissolved organic matter: A comparison with...

After composting, the land application of silkworm excrement (SE) solid waste is a feasible treatment method for contaminated soil. However, the composition and structure of the dissolved organic matter (DOM) in SE compost during composting, and the implications of these changes on the DOM's electron transfer capacity (ETC), remain unclear. This lack of clarity hinders the effective utilization of compost products. Hence, to address the issue, this study focused on the unknown ETC of DOM in lignin-rich SE compost using protein-rich sewage sludge (SS) compost as a reference and analyzed the spectral characteristics, electron-accepting capacity (EAC), electron-donating capacity (EDC), native reducing capacity (NRC), and chemical reducing capacity (CRC) of DOM at different stages during composting. The results revealed that SE composting remarkably improved microbial humic-like (C1)/fulvic-like (C3) substances and reduced protein-like substances (C2) in DOM compared to SS composting. Meanwhile, SE composting had a noticeable positive effect on the aromatization of DOM. Moreover, the SE-compost DOM obviously increased EAC/EDC in the final compost by 18.1 %/8.0 %, and increased NRC/CRC by 4.9 %/83.4 % compared to the SS-compost DOM. These results showed that SE-compost DOM can be used as a useful amendment in soil remediation. Further investigation is suggested to focus on the effective utilization of the SE-compost DOM for enhancing heavy metal detoxification in soil remediation.