Enhancement of Humification in the Fermentation of Swine Manure Using Tobacco Dregs and Manganese Dioxide

Abstract

This paper investigates on the humification of SM in the process of anaerobic digestion or anaerobic-aerobic fermentation (AAF) by adding tobacco dregs (TD) and MnO2. The results illustrate that in AD, the addition of TD and MnO₂ had a significant impact on the humification of SM, increasing the humus (HS) content by 52.17%. In AAF, the addition of MnO₂ increased the HS content by 63.15%, but the addition of both TD and MnO₂ did not have a significant effect on humification. The primary functional groups of HS were amino sugars and phenolic hydroxyl groups in the processes of both AD and AAF. In AD, HS formation was predominantly driven by the Maillard reaction, whereas in AAF, the HS structure was more complex and contained a higher proportion of phenolic groups. EEMs revealed that HA was the predominant component of HS in both AD and AAF, but the fluorescence intensity of HA in AAF was lower than that in AD. Addition of TD enhanced the hydrolysis in both AD and AAF, while MnO₂ could promote the humification in AD. Addition of TD and MnO₂ improved the hydrolysis of SM in both AD and AAF, and enhanced humification of SM in AD. This study explored an efficient humification pathway for SM through addition of TD and MnO2, providing a new cost-saving strategy to enhancing SM utilization efficiency and mitigating greenhouse gas emissions in AD.

Keywords: tobacco dregs, MnO2, Humification, Anaerobic digestion, anaerobic-aerobic fermentation