## 3 Result
### Dual-Step Process  
In order to identify the most effective process for stabilizing the organic fraction of solid waste (OFMSW), two different methods have been performed on the grinded OFMSW: UV/ozone radiations and thermal treatments.  
Figure 3B reports the results obtained by microbiological tests performed on OFMSW samples exposed to UV/ozone radiations as a function of time exposure, ranging from 1 h to 5 h. The untreated  
Figure 3: (**A**) TGA and derivative (DTG) curves of OFMSW; (**B**) Bacterial growth on OFMSW samples subjected to UV/ozone stabilization; (**C**) Enlargement (25 \({}^{\circ}\)C–200 \({}^{\circ}\)C) of TGA curves of OFMSW before and after 2 h UV/ozone treatment.  
sample showed a high level of contamination by different types of bacteria, as demonstrated by the presence of colonies with different shape, size and pigmentation on the agar plate. After 2 h of UV/ozone treatment, the bacterial growth starts to decrease and, although non-completely removed, it was further reduced until 5 h. Unfortunately, longer UV/ozone exposure caused the degradation of the organic fraction. For these issues, a time of exposure equal to 2 h was selected to obtain an adequate compromise time-effectiveness avoiding damage of OFMSW. Besides reduction of the bacterial activity, UV/ozone treatment also caused a significant water evaporation, as observed by TGA analysis reported in Figure 3A and by the enlargement of the TGA curves ranging from 25 \({}^{\circ}\)C to 200 \({}^{\circ}\)C, reported in Figure 3C. The TGA curves evidence that the residual water content of the OFMSW after a two-hour long irradiation process with UV lamp is about 12%.  
In order to overcome the low effectiveness of UV/ozone stabilization process, another sterilization technique was explored by using a thermal treatment [20]. Microbiological tests performed on each OFSMW sample after each thermal treatment investigated are reported in Figure 4.  
By comparing the microbiological results reported in Figure 4, it is evident that all the thermal treatments were effective to completely sterilize the OFMSW samples. In Figure 4, the untreated sample resulted fully contaminated with a wide variety of microorganisms while no growth of bacterial colonies was observed on the plates related to the treated samples. High temperatures effectively killed the microorganisms; nevertheless, the third treatment (20 min at 120 \({}^{\circ}\)C) was selected as the most convenient sterilization treatment in terms of times, feasibility and efficacy, even if it causes an almost full removal of the water content.  
In addition, the dual-step process allowed obtaining samples which are characterized by adequate mechanical properties, as following reported. However, the process is quite inefficient from the energetic and materials consumption point of view. In facts, starting from a OFMSW very rich in water, this is firstly heated to remove bacterial activity. Despite the fact that the use of a climatic chamber allows reducing the water loss, when working in a forced convection oven, water is completely evaporated. In any case further water must be added to produce the slurry, which is again heated up to 120 \({}^{\circ}\)C to allow matrix curing (see Figure 1). Combining sterilization and curing was attained in a single step process, with the advantage that the material is heated only once up to 120 \({}^{\circ}\)C and no further water is added to the slurry.