## 3 Results and Discussion
### Applicability of Moring as a Flocculant for Microalgae Grown on Digestate  
This study proposed using the seed powder of _Moringa oleifera_ as a bioflocculant for harvesting green microalgae grown on digestate for feed production. A dosage between 100-500 mg L\({}^{-1}\) was found to give the highest harvesting efficiencies (around 80%), representing a ratio of microalgae: flocculant between 5:1 and 1:1. This is similar to the ratio found by [PERSON] et al. [21] of 1:1 for _C. vulgaris_ and 1.5:1 for _S. obliquus_, and is also in the same range of several other studies, including one of the first reports of _Moringa_ as a bioflocculant for microalgae harvesting [18].  
The amount of _Moringa_ seed powder needed for achieving high harvesting efficiencies greatly surpasses that of other bioflocculants by a factor of 10 or more; this has been considered a disadvantage as it results in high costs with flocculant addition and a greater amount of generated \"sludge\" [21]. Such conclusions are made taking into consideration that the seed powder would be used only as a flocculant with no added value for the final product. Nevertheless, _Moringa_ seed has been recently shown as a good protein source and a beneficial additive to animal feed [49; 50]; the used _Moringa_ seed powder in this study, for instance, had 39% protein in its composition. Moreover, the use of a mixture of microalgae and _Moringa_ leaves was shown to have synergistic effects as a feed for goats [51], and a similar result could potentially be found when evaluating the use of a mixture of microalgae with _Moringa_ seeds. Therefore, the final obtained product of microalgae-_Moringa_ could potentially have a higher nutritional value than only the microalgae itself.  
Furthermore, the use of _Moringa_ seed powder as a flocculant enabled the reuse of the cultivation water and had a positive effect on the biosynthesis of polyunsaturated fatty acids, especially \(\alpha\)-linolenic acid (C18:3 \(\omega\)3), which is one of the essential fatty acids that need to be externally acquired in the human diet [52], possibly further increasing the added value of using _Moringa_ as a bioflocculant for microalgae harvesting. Finally, even though [PERSON] et al. [21] calculated increased cost when using _Moringa_, the environmental impacts of the alternatives should be considered. This study showed that a simple mill grinding was effective in upscaling the production of the used seed powder and that different granulometries did not impact the harvesting efficiency, resulting in a low-energy and zero-chemical process for the production of the flocculant. The production of tannin-based flocculants, identified by [PERSON] et al. as the most promising of the ones tested in their study, includes several process steps, including the use of a chemical modification with significant environmental impact [53].  
One point of attention in this study was the high content of Fe and Al in the microalgae grown on digestate and harvested with _Moringa_ seed powder. Since the algae biomass would likely be only one component in a feed formulation, the high Fe and Al contents would become diluted in the complete feed and would not pose any problems for animal nutrition. Nevertheless, the high final contents of these metals in the algae cultivated in digestate and harvested with MP should be a point of attention in future studies.