## 4 Conclusions  
This study demonstrated that a fractionation approach might constitute a new and promising route for converting olive pomace into multiple value-added products, like added-value energy applications without throwing away high-value compounds with food application. The first step (wet fractionation) leads to the production of a liquid fraction (yield of 9% in dry weight) rich in minerals (\(\approx\)11 g/100 g), sugars (mainly mannitol: 21-32 g/100 g), and phenolic compounds (mainly hydroxytyrosol: 514-626 mg/100 g), but also has the advantage of optimising the drying process of the solid fraction. The dry fractionation allowed for attaining a stones fraction (yield of 20-26% in dry weight) with significant calorific power (\(\sim\)19 MJ/kg) and a pulp fraction (yield of 65-71% in dry weight), which is a relevant source of antioxidant dietary fibre with a neutral detergent fibre content of 53-59 g/100 g and a significant antioxidant activity not only in free phenolics (ORAC: 455-503 \(\upmu\)M trolox equivalents/g) but also in bound phenolics (ORAC: 121-130 \(\upmu\)M trolox equivalents/g).  
Considering the yield, the chemical composition and the in vitro antioxidant activity of both edible fractions, this approach allowed to obtain two sources of food ingredients: an enriched phenolic-mineral-sugar extract (liquid fraction) with potential application as a food preservative or health-promoting food ingredient, and a source of antioxidant dietary fibre (pulp fraction). At the same time, impurities such as the olive pulp and the small piece of stones related to emission, corrosion and slagging were removed to obtain a solid biofuel with better performance.  
In the future, optimisation studies should be performed in combination with life cycle analysis (LCA) to improve the sustainability and economics of the fractionation approach proposed in this study. To guarantee the application of olive pomace fractions to develop new food ingredients, future studies about the safety, bioactivity and stability/bioaccessibility of its bioactive compounds will be necessary. At a pilot-scale, the replacement of the centrifugation without refrigeration and freeze-drying (adopted at the lab-scale) by mechanical pressing and conventional drying techniques respectively, could be feasible options to ensure a more affordable process.  
The following are available online at [[http://www.mdpi.com/2076-3417/10/19/6785/s1](http://www.mdpi.com/2076-3417/10/19/6785/s1)]([http://www.mdpi.com/2076-3417/10/19/6785/s1](http://www.mdpi.com/2076-3417/10/19/6785/s1)), Figure S1: Distribution (in percentage) of the phenolic compounds from olive pomace and its fractions identified by LC-ESI-UHR-QqTOF-MS.  
Conceptualisation, methodology, validation, formal analysis, M.P. and T.B.R.; Investigation, data curation, writing--original draft preparation, T.B.R.; Supervision, project administration, funding acquisition, writing--review and editing, M.P.; Supervision, writing--review and editing, A.A.V. and J.N.; Methodology, writing--review and editing, A.L.O. and C.C. All authors have read and agreed to the published version of the manuscript.  
This research was funded by National Funds from FCT--Fundacao para a Ciencia e a Tecnologia, through the project MULTIBIOREFINERY-SAKTPAC/0040/2015 (POCI-01-0145-FEDER-016403) and the project \"Biological tools for adding and defending value in key agro-food chains (bio-n2-value)\", n\({}^{\circ}\) NORTE-01-0145-FEDER-000030, funded by Fundo Europeu de Desenvolvimento Regional (FEDER), under Programa Operacional Regional do Norte-Norte2020. We would also like to thank the scientific collaboration under the FCT project UID/Multi/50016/2019.  
The authors declare no conflict of interest.