## 3 Results and Discussion  
### Fractionation Approach  
The wet and dry fractionation applied to crude olive pomace samples from OM 1, and OM 2 was shown to be reproducible. The yield (% DW) for the different fractions was similar for both crude olive pomace samples. Figure 1 presents the proposed process for \"zero waste\" valorisation of olive pomace, including the principal mass balances. The first step of wet fractionation (centrifugation) led to two different fractions: sediment and supernatant. The sediment (solid fraction) was the most representative fraction for both crude olive pomace samples (63-53% of crude olive pomace fresh weight). As a result of this first fractionation, the moisture and sugar concentration of solid fraction were reduced, facilitating its drying, and the crude olive pomace phenolics were recovered mainly in the liquid fraction (supernatant) [18]. In the present approach, the wet fractionation (centrifugation)followed by freeze-drying allowed to obtain 0.02 to 0.03 kg of liquid fraction from 1 kg of the wet olive pomace, showing a yield of 9% (DW) for both crude olive pomace samples analysed. A higher water loss occurred during the drying of liquid and solid fraction from OM 2 due to their higher moisture (liquid fraction: \(95.29\pm 0.81\), solid fraction: \(68.18\pm 1.86\)) than the liquid and solid fraction obtained from OM1 (liquid fraction: \(88.64\pm 0.36\), solid fraction: \(62.07\pm 0.08\)).  
After the drying step and dry fractionation (milling and sieving), two different fractions were obtained, the stones and pulp fraction. For both crude olive pomace samples (0.16-0.23 kg from 1 kg of wet olive pomace), pulp fraction had the highest yield (% DW) around 65% and 71% for the OM 1 and OM 2 samples, respectively. On the other hand, a yield (% DW) between 20% and 26% was attained for the stones fraction.  
Other fractionation approaches have been applied to olive pomace [17; 18]. [PERSON] et al. [18] obtained an extract rich in phenolic compounds and olive pomace oil from the liquid fraction and a solid biofuel from the solid fraction. The simple conversion of the solid fraction in solid biofuel neglected not only the high value of the compounds like fibre and phenolics presented in this fraction but also compromised its performance as a solid biofuel due to the risk of occurrence of uncontrolled combustion triggered by the presence of fat and small particles [12]. On the other hand, [PERSON] et al. [17] ignored the energy potential of the stones fraction completely, using a considerable amount of water prior to centrifugation and discarded a considerable amount of olive pomace pulp fraction (not using a dry fractionation step to separate the pulp from stones). Neither of these two studies reported the yields of each of the fractions obtained from olive pomace fractionation. Besides that, the approaches reported in the literature have not explored the whole olive pomace fractions' potential, compromising not only the quality of the added-value products but also the \"zero waste\" goal. In contrast, the fractionation approach proposed in this work appears to be a promising and sustainable alternative to create different added-value products from olive pomace biomass without any consumption of water nor chemicals, and firstly, prioritising higher value applications and lastly, the energy valorisation according to circular bioeconomy principles [36].