## 3 Results and Discussion  
### Sunflower Husk Ashes Composition  
The results for the SHA major compounds in their oxide forms are presented in Table 2. The SHA samples consist mainly of K\({}_{2}\)O in the range of 12.0-44 wt. %, P\({}_{2}\)O\({}_{5}\) in the range of 1.4-10.5 wt. %, MgO in the range of 7.3-16.1 wt. %, SO\({}_{3}\) in the range of 3.1-15.8 wt. %, CaO in the range of 11.7-33.8 wt. %, and Fe\({}_{2}\)O\({}_{3}\) up to 1.9 wt. %. The main reason for the wide range of the obtained composition is that the sunflower plants involved in the first industrial processes grow in different soil based on their geographical location and use additives and fertilizers [31].  
The results correspond well with the analyses performed in other studies [32; 33]. The key compounds related to our research work are potassium and phosphorous, due to the targeted bio-fertilizers consisting of 30 wt. % K\({}_{2}\)O and 5 wt. % P\({}_{2}\)O\({}_{5}\). Ash samples SHA7-S and SHA13-S are the only powdered materials that could be directly subjected to granulation due to their similarity of composition to the target. All the other analyzed samples have to be used in mixture by each other; SHA1-F, SHA4-F, SHA5-F, and SHA15-S are additives suitable for increasing the potassium content. Analogously, samples SHA2-F, SHA3-S, SHA9-S, and SHA12-S could be used as additives for phosphorous enrichment of the final product. The results show that the sampling place is crucial for the composition of SHA, as the concentration of K\({}_{2}\)O drastically reduced in the storage place compared to in the filter collectors, which could be explained by the potassium's dissolution in rainwater. The presence of SO\({}_{3}\) in all samples benefits the properties of the raw materials because sulfur is essential for various plants' growth functions, like nitrogen metabolism, enzyme activity, and oil synthesis [34].  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \multirow{2}{*}{**Sample**} & **K\({}_{2}\)O** & **P\({}_{2}\)O\({}_{5}\)** & **Fe\({}_{2}\)O\({}_{3}\)** & **MgO** & **SO\({}_{3}\)** & **CaO** \\  & **wt. \%** & **wt. \%** & **wt. \%** & **wt. \%** & **wt. \%** & **wt. \%** \\ \hline SHA1-F & 40.9 & 4.5 & 0.0 & 7.3 & 7.2 & 14.8 \\ SHA1-S & 30.7 & 4.0 & 0.3 & 9.3 & 7.4 & 22.5 \\ SHA2-F & 17.9 & 9.2 & 0.6 & 15.3 & 4.1 & 29.0 \\ SHA2-S & 24.6 & 6.6 & 0.3 & 13.8 & 7.1 & 22.7 \\ SHA3-S & 22.5 & 10.5 & 0.2 & 14.9 & 3.8 & 24.4 \\ SHA4-F & 39.4 & 1.5 & 0.0 & 14.1 & 3.7 & 17.8 \\ SHA4-B & 12.0 & 7.4 & 1.9 & 15.1 & 3.7 & 33.8 \\ SHA4-S & 30.8 & 3.8 & 0.3 & 9.3 & 7.4 & 22.5 \\ SHA5-F & 40.0 & 1.4 & 0.1 & 11.2 & 6.5 & 16.9 \\ SHA5-B & 23.2 & 6.3 & 0.3 & 13.9 & 3.6 & 24.5 \\ SHA6-S & 18.9 & 6.5 & 0.9 & 15.5 & 4.0 & 25.7 \\ SHA7-F & 32.7 & 7.8 & 0.3 & 12.3 & 4.4 & 19.9 \\ SHA7-S & 32.5 & 5.2 & 0.4 & 12.5 & 4.5 & 21.1 \\ SHA8-S & 22.9 & 6.3 & 0.4 & 14.7 & 3.1 & 29.0 \\ SHA9-S & 20.3 & 9.5 & 0.4 & 16.1 & 7.2 & 18.3 \\ SHA10-S & 22.8 & 3.9 & 0.4 & 16.0 & 6.9 & 22.4 \\ SHA11-S & 23.5 & 6.9 & 0.6 & 15.4 & 3.4 & 28.9 \\ SHA12-S & 20.3 & 9.0 & 0.5 & 14.8 & 4.1 & 27.9 \\ SHA13-S & 33.0 & 5.9 & 0.4 & 11.7 & 4.3 & 21.7 \\ SHA14-S & 30.9 & 6.3 & 0.3 & 11.7 & 6.1 & 22.3 \\ SHA15-S & 44.0 & 3.8 & 0.0 & 7.3 & 15.8 & 11.7 \\ SHA16-S & 26.9 & 8.9 & 0.3 & 13.7 & 5.7 & 24.1 \\ \hline \end{tabular}
\end{table}
Table 2: Composition of the investigated sunflower husk ashes.