Compost Biodegradation by ¹H Magnetic Resonance and Quantitative Relaxation Tomography Check Access

The collection and composting of organic waste from both households and industries has long been recognized as a valuable contribution to waste management. The first step towards a “zero-waste” concept, in particular in the food processing sector, is the identification, quantification and characterization of residues. Thus considerable efforts have been focused towards the definition of compost maturity in order to decide on the quality of compost. Therefore the principal requirement of a compost for its safe use is a high degree of maturity, which implies a stable organic matter (OM) content and the absence of phytotoxic compounds and plant or animal pathogens. Magnetic Resonance Relaxometry (MRR) and Imaging (MRI) of hydrogen nuclei are optimal candidates to give information on the degree of degradation and maturity of compost, especially when there is needed a careful non-invasive and non-destructive characterization. Because many foods are proton-rich, e.g., from water, fat, carbohydrates, and proteins, MRR is a common tool to gain information about the composition and internal structure of foods, permitting also to monitor the compositional and structural modifications when they undergo natural or artificial processes. Since the relaxation times (longitudinal T₁ and transverse T₂) variations change the image contrast, MRI can easily monitor the structural changes in foods during processing and storage. MRI can detect and show internal variations in the water content, as well as changes in water interaction with cellular tissues. In this work typical MRR parameters as T₁ and T₂, and ¹H signal amplitude were related to water content, and to micro and molecular structure of the compost itself, to follow the compost phases. Furthermore the authors used Quantitative Relaxation Tomography (QRT), a method to measure locally the relaxation times by means of MRI images. This technique allowed them to locally follow the FW biodegradation over time and to evaluate the maturity and quality parameters. In summary, matching magnetic resonance techniques with other standard analyses could be of great importance to fully describe the stages of composting and define the degree of compost maturity.