## 4 Conclusions  
The optimum dose of 0.5 g L\({}^{-1}\) MP (biomass/flocculant ratio of 1) resulted in a harvesting efficiency of around 80%, while the use of water extract of MP at 3 g L\({}^{-1}\) (biomass/flocculant ratio of 0.17) resulted in a harvesting efficiency of 91%. Therefore, _Moringa oleifera_ seed powder was found to be an effective flocculant for harvesting a mixed algal culture grown on digestate, especially when using a water-extraction step during the flocculant preparation. The robustness of this flocculant makes it attractive for industrial applications, but more studies are needed to evaluate its economic viability and environmental impacts. Finally, the characterization of the trace element composition of the final biomass proved to be of importance and can help to guide further developments in the field aiming at obtaining high harvesting efficiencies together with high-quality biomass.  
The following supporting information can be downloaded at [[https://www.mdpi.com/article/10.3390/app122412968/s1](https://www.mdpi.com/article/10.3390/app122412968/s1)]([https://www.mdpi.com/article/10.3390/app122412968/s1](https://www.mdpi.com/article/10.3390/app122412968/s1)), Figure S1. 1.5 % agarose gel electrophoresis results of gDNA isolated from the seed samples of _Moringa sp._ obtained from India. Figure S2. 1.5% agarose gel electrophoresis of PCR analysis of isolated seed samples of _Moringa_ using _rbcl._ and _trnH-psbA_ primers. Figure S3. Harvesting efficiency of _Moringa oleifera_ seed powder (MP), aluminium sulfate (AS), and iron (III) chloride (IC) added to a mixed culture of _Desmodesmus_ and _Chlorella_ (500 mg L\({}^{-1}\)) at 200 mg L\({}^{-1}\). Figure S4. Influence of pH values in the harvesting efficiency of aluminium sulfate (AS) and iron (III) chloride (IC). The different pH values were obtained by the addition of either AS or IC solutions to the microalgae suspension, resulting in different final concentrations of each flocculant for a given pH. Figure S5. Effect of different duration combinations for the coagulation and flocculation steps when using _M. oleifera_ seed powder for the harvest of a mixed culture of _Chlorella_ and _Desmodesmus_ (seed powder concentration of 500 mg L\({}^{-1}\), pH 8, coagulation and flocculation rotation speeds of 150 rpm and 30 rpm, respectively). The effect of sedimentation duration (20, 40, or 60 min) on the harvesting efficiency is also shown. Different letters indicate significant differences between the flocculation times after a one-way ANOVA followed by a Tukey test (\(p<0.05\)). Figure S6. Effect of three different granulometries of _Moringa oleifera_ seed power on the flocculation efficiency at 60 min sedimentation (seed powder concentration: 0.5 g L\({}^{-1}\), the rotation speed and time used were 150 rpm for 5 min followed by 30 rpm for 10 min).  
M.K.: conceptualization, investigation, writing--draft preparation, D.T.: conceptualization, investigation, writing--draft preparation, E.E.D.: writing--review and editing, E.M.:writing--review and editing, supervision, and funding acquisition. M.F.d.S.: conceptualization, writing--review, editing, and supervision. All authors have read and agreed to the published version of the manuscript.  
This research was financially supported by the European Union's Horizon 2020 project Nutri2 Cycle (Grant agreement No. 773682) and by the European Regional Development Fund within the Interreg North-West Europe programme, ALG-AD, project NWE520, co-financed by the Province West-Vlaanderen, Belgium.  
Not applicable.  
The authors would like to thank [PERSON] for the supply of the algae cultures and _Moringa_ seeds used and for introducing the first and last authors to each other.  
The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.