Insights on the aerobic biodegradation of agricultural wastes under simulated rapid composting conditions

Abstract

Knowledge of organic matter transformation under simulated rapid composting is essential for the understanding of biodegradation processes. Herein, several technologies, including atomic force microscope (AFM), X-ray photoelectron spectroscopy (XPS) and 13C Nuclear Magnetic Resonance Spectroscopy (13C NMR) were used to gain insight of the composition and architecture of the substrate during biodegradation. The total carbon of the substrate was decreased by 27.7% compared to the initial content, while the total nitrogen was increased from 1.1% to 1.8% at the end. The water soluble carbon, water soluble nitrogen and hydrolytic enzyme activities fluctuated strongly between 3 and 14 days, which was considered as the active stage of the composting process. The appearance of microfibers and deep ditch indicated that the tunneling might be one of the mechanisms of the composting microorganisms to degrade the lignocellulose. The X-ray photoelectron spectroscopy (XPS) analysis results showed that the main degradable carbon component was C1 (containing C-H or C-C bonds), which was decreased by 25.5% compared to the initial substrate. The 13C NMR analysis showed that the O-alkyl-C group dominated the resonance signals in all treatments ranging from 76.6% to 83.1% and alkyl-C fluctuated from 8.1% to 10.2%, indicating the effective degradation of lignocellulose. In summary, the combination of morphological observations by atomic force microscope (AFM) and the chemical analysis by XPS and 13C NMR is a promising approach for the characterization of agricultural wastes biodegradation process.