# Exploring the Bioethanol Production Potential of _Miscanthus_ cultivars
## 3 Results and Discussion
### Elemental Composition of Cultivars through the Growing Season  
The elemental composition of the _Miscantlus_ cultivars was measured during the growing season, and analysis revealed a decrease in the presence of elements over the time period. Analysis also revealed that there were differences in the element levels between the cultivars. Determining the presence of potassium, magnesium, sodium, sulphur and phosphorus revealed a significantly higher potassium concentration compared to other elements (Figure 5A-E). Analysis revealed that elements are slowly lost from the plants during the growing season. The majority of the elements (Mg, S, P and Na) exhibited a constant reduction over the time period; however, potassium levels appeared to drop significantly between the harvest points of 26 November 2018 and 14 December 2018 and in Cultivars C-F (Figure 5A-D). Cultivar G had significantly higher initial potassium levels (7596 \(\pm\) 198 ppm) compared with the other cultivars (3800-6800 ppm); this cultivar also had the highest phosphorus levels, but sodium, magnesium and sulphur contents were analogous with other cultivars. Cultivar G also had higher potassium levels during the growing season; this cultivar only showed a reduction in potassium levels at a later harvest  
Figure 4: Sugar profiles of the hydrolysate of various _Miscantlus_ cultivars harvested at specific time-points. Data representative of triplicate values. Harvest dates are 1 November 2018, 20 November 2018, 14 December 2018, 16 January 2019, 5 February 2019 and 7 February 2019.  
\begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**Cultivars**} & \multicolumn{2}{c}{**Lignin (ABSL) (\%, \(w\)/\(w\))**} \\ \cline{2-3}  & **November** & **February** \\ \hline Cultivars C & 25.00 & 21.38 \\ Cultivars D & 18.78 & 22.43 \\ Cultivars E & 22.22 & 22.25 \\ Cultivars F & 21.56 & 23.71 \\ Cultivars G & 17.56 & 21.98 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Lignin content of _Miscantlus_ Cultivars C–G.  
date (16 January 2019). Cultivar E had significantly lower phosphorus content (278.8 \(\pm\) 17.9) when compared with the other cultivars at the early time-points (619-1048 ppm).  
In the UK, typical seasonal changes result in the senescence of _Miscanthus_ before the initial harvest date in November. During senescence, the translocation of minerals and nutrients occurs from the leaves and stems into the plants' rhizomes. It is documented that between November and February harvests, there are minimal changes to the above-ground plant, once it has senesced, until spring and summer, when the plant begins to grow again (25). However, the results obtained in this study suggested later senescence occurred between November and February. For Cultivar G, the grass normally remains green until February; this fits the potassium profile (Figure 5A) very well. Another possible explanation of the decrease in mineral composition in the sample is the result of leaf abscission, as the samples used in this study were a mixture of milled stems and leaves. Therefore, the ratio of leaf-to-stem matter could vary between samples harvested at different dates, resulting  
Figure 5: Elemental composition of potassium (**A**), magnesium, sodium, phosphorus and sulphur (**B**) (ppm) of _Miscanthus_ cultivars harvested at specific time-points. Data representative of triplicate values. Harvest dates are 1 November 2018, 20 November 2018, 14 December 2018, 16 January 2019 and 5 February 2019.  
in changes to the nutrient and mineral contents in the same plant [26]. This could also contribute to the variances seen between cultivars.