## 2 Materials and Methods  
### Sample Collection and Preparation for NMR  
The samples were supplied from another department of the project and the experimental details of this process are given outside this work, with only the highlights being reported below. The waste used for the Fenton treatment was obtained through a sampling procedure lasting 12 days. In each of these days, waste was taken from a group of four different families, each day a different one. The waste collected on each sampling day (about 5 kg) was mixed and milled to a millimeter size by means of a steel blender. The resulting minced material was stored at \(-20\)\({}^{\circ}\)C for 12 days. After this time, all the daily rates were defrosted and mixed together; the material obtained was divided into bags of 200 g, re-frozen and then used, after heat treatment at 110 \({}^{\circ}\)C, as the starting matrix for the oxidative treatment. The oxidation reaction [18] was carried out using a laboratory-scale glass reactor apparatus. The sample of organic material, 200 g, was placed into the glass rector and the Fenton reagents were added: 10 mL of a FeSO4 solution followed by addition of 10 mL of hydrogen peroxide (H2O2) solution. The mixture was kept under stirring conditions, the reactor was placed in a water bath, and the internal temperature was kept at 60 \({}^{\circ}\)C for the duration of the reaction. The pH of the mixture, initially at 4.5, was allowed to decline to pH 3.0 and was maintained until the reaction was complete. The samples used for the NMR experiments were collected during the phases of oxidation procedure and were differentiated according to the different percentages of H2O2/FeSO4 used. A first sample, called Sample 0, was collected from the batch of organic waste subjected to heat treatment (110 \({}^{\circ}\)C for 48 h). Three samples, called Sample 1, Sample 2, and Sample 3, were collected, and waste was treated for 12 h with the same amount of FeSO4, 0.05%wt, but different concentrations of H2O2, i.e., 0.002%wt, 0.0015%wt, and 0.0006%wt respectively. In order to understand the transformations that the waste undergoes during the oxidation process and to investigate the best experimental conditions, samples were collected at regular intervals during two different process (process A and process B). For process A, carried out by treating the waste with a solution of 0.002%wt of H2O2 and 0.01%wt of FeSO4, four samples were collected by withdrawing the substance from the reaction flask at regular 3 h intervals, i.e., Sample 4_3 h, Sample 4_6 h, Sample 4_9 h and Sample 4_12 h. Other four samples were collected for process B, carried out by adopting the conditions of Sample 3 (0.0006%wt of H2O2 and 0.05%wt FeSO4), i.e., Sample5_3 h, Sample 5_6 h, Sample 5_9 h and Sample 5_12 h, always at 3 h intervals. Moreover, another sample was collected for process B after a complete process of 8 h, Sample 6_8 h. This sample was collected in order to check if the reaction is complete after 8 h, as reported in reference [22], where the authors applied the Fenton reaction to an anaerobic digestate sample. In Figure 1, the experimental steps, the reaction conditions and the NMR samples collected during all oxidative treatments are reported. For the NMR experiments, samples were prepared by inserting 50 mg of substance into 5 mm zirconium rotor with 0.05 mL of D\({}_{2}\)O and a small amount of TMS. The D\({}_{2}\)O was used as the field frequencies lock signal and TMS for internal referencing of \({}^{13}\)C chemical shifts. No additional treatment was necessary.