Studies of Organic Matter in Composting, Vermicomposting, and Anaerobic Digestion by 13C Solid-State NMR Spectroscopy

Abstract

Composting, vermicomposting, and anaerobic digestion are three commonly applied processes for the transformation of organic waste into valuable products for soil amendment. The application of compost, vermicompost, and digestate to soil requires specific properties, such as maturity and stability, strongly related to the composition of organic matter. 13C solid-state Nuclear Magnetic Resonance (SSNMR) has often been applied to follow the transformation of organic matter during waste treatment processes, as well as to assess the quality of the produced amendments and the effectiveness of the treatments. Thanks to the possibility of associating the 13C chemical shift to different functional groups of biomacromolecules present in the waste feedstocks and in the final products, thorough characterizations of organic matter have been performed exploiting 13C cross-polarization magic angle spinning experiments, and semiquantitative descriptions of the evolution of the different groups during composting, vermicomposting and anaerobic digestion have been reported. Here, these studies are reviewed with the aim of highlighting the potential of the application of 13C SSNMR to these complex materials, as well as the critical issues and perspectives.

Comparative Study of Vermicomposting: Apple Pomace Alone and in Combination with Wheat Straw and Manure

“…The reduction in organic matter during vermicomposting was consistently followed by a significant increase (p < 0.05) in mineral content [57,58]. The observed rise in mineral content across all the experiments during vermicomposting aligns with the documented increase in individually examined macroelements (see Table 2).…”

“…During the vermicomposting process, earthworms and microorganisms synergistically contribute to the degradation and transformation of organic matter in substrates, resulting in the reduction and stabilization of the final product of vermicomposting. Typical chemical changes during the bio-oxidation of organic matter involve the processes of partial mineralization and humification [57,58]. As demonstrated in Table 1, the organic matter content in all our vermicomposts is significantly lower (p < 0.05) compared to the initial raw materials, indicating that the earthworms expedited the decomposition of the organic matter [59].…”

Testing biowaste materials as peat replacement in organo-mineral fertilizers

“…Using the Alkyl C/O Alkyl C ratio (Baldock et al, 1997;Pizzanelli et al, 2023) and the humification degree (Zaccone et al, 2018) as indicators of C org stability, it is shown that Peat would be more difficult to degrade in soil than GC, MSWC and VC. However, with no differences in N-NH 4 + and N-NO 3 − concentrations it was not possible to confirm the hypothesis that the granule integrity will slow down the N release.…”

Exploring the Untapped Potential of Pine Nut Skin By-Products: A Holistic Characterization and Recycling Approach

“…The techniques utilized for the morphological-structural characterization of the PNS samples include Fourier Transform Infrared (FT-IR) spectroscopy, solid-state CP/MAS 13C NMR spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and the volumetric analysis of nitrogen adsorption. By employing these techniques, a comprehensive morphologicalstructural characterization of the sample can be achieved, aiding in the understanding of its properties and potential applications [75].…”