# Assessment of Areal Methane Yields from Energy Crops in Ukraine, Best Practices
## 3 Results and Discussion
### Sweet Sorghum  
Four varieties of sweet sorghum (species _Sorghum saccharatum (L.[PERSON]_) were analysed: \"Sylosne 42\", \"Favoryt\", \"Zubr\", and \"Mamont\". The selected varieties have the following characteristics and recommended growing zones in Ukraine: \"Sylosne 42\" and \"Favoryt\" grow best in the Polesia zone with mid-ripening group of ripeness; \"Zubr\" grows best in the steppe and forest-steppe; \"Mamont\" grows best in the steppe zone with mid-ripening group of ripeness. The values of DM\({}_{\rm FM}\), VS\({}_{\rm DM}\), DMY and crop N uptake are provided in Table 4; the SMY, AMY and BBCH-codes of the sweet sorghum samples are given in Figure 3. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Cultivar** &
\begin{tabular}{c} **Harvesting** \\ **Time** \\ \end{tabular} & **DM\({}_{\rm FM}\) *, [\%]** & **VS\({}_{\rm DM}\) **, [\%]** & **DMY ***,** & **Crop N Uptake,** \\  & & **Time** & **[t\({}_{\rm DM}\) ha\({}^{-1}\)]** & **[kg\({}_{\rm N}\) ha\({}^{-1}\)]** \\ \hline Favoryt & H1 & 19.7 (0.89) & 92.6 (4.17) & 14.2 (0.64) & 136.8 (6.16) \\ Mamont & H1 & 24.0 (1.08) & 92.8 (4.17) & 17.8 (0.80) & 284.6 (12.8) \\ Sylosne 42 & H1 & 22.3 (1.00) & 94.1 (4.24) & 11.0 (0.49) & 76.8 (3.46) \\ Zubr & H1 & 23.8 (1.07) & 92.8 (4.18) & 12.7 (0.57) & 178.1 (8.01) \\ Favoryt & H2 & 20.9 (0.42) & 95.3 (1.91) & 15.1 (0.30) & 145.1 (2.90) \\ Mamont & H2 & 23.6 (0.47) & 94.5 (1.89) & 17.5 (0.35) & 279.8 (5.60) \\ Sylosne 42 & H2 & 22.6 (0.45) & 94.1 (1.88) & 11.1 (0.22) & 77.9 (1.56) \\ Zubr & H2 & 24.1 (0.48) & 92.3 (1.85) & 12.9 (0.26) & 180.3 (3.61) \\ Favoryt & H3 & 24.0 (0.67) & 95.9 (2.68) & 17.4 (0.49) & 166.7 (4.67) \\ Mamont & H3 & 23.4 (0.66) & 95.1 (2.66) & 17.3 (0.49) & 277.5 (7.77) \\ Sylosne 42 & H3 & 23.8 (0.67) & 94.9 (2.66) & 11.67 (0.33) & 81.8 (2.29) \\ Zubr & H3 & 24.8 (0.69) & 95.8 (2.68) & 13.3 (0.37) & 185.6 (5.20) \\ \hline \hline \end{tabular}  
* The dry matter content related to fresh matter, ** Volatile solids content related to dry matter, *** Dry matter yield.  
\end{table} 
Table 4: Sweet sorghum: DM and VS- content at harvest time, dry matter yield per hectare and N-uptake. Units are given in square brackets. Values are given as mean; standard deviation is given in round brackets. The vegetation stages of the samples for the three analysed harvesting times varied between the stage of shooting/the appearance of the last leaf (BBCH-code 37) and the mid-stage of milk ripeness (BBCH-code 75). The H3 harvesting time was related to the period between the mid-stage of inflorescence (earing) and the mid-stage of milk ripeness (BBCH-codes 55-75). The sweet sorghum samples harvested at H3 had the highest average values of DM\({}_{\text{FM}}\) (\(23.99\pm 0.59\%\)), VS\({}_{\text{DM}}\) (\(95.43\pm 0.48\%\)), DMY (\(14.91\pm 2.89\) t\({}_{\text{DM}}\) ha\({}^{-1}\)), crop N uptake (\(177.88\pm 80.26\) kg\({}_{\text{N}}\) ha\({}^{-1}\)), SMY (\(0.33\pm 0.02\) m\({}^{3}\) kg\({}^{-1}\)VS) and AMY (\(4767.17\pm 1125.41\) m\({}^{3}\) ha\({}^{-1}\)). As shown in Figure 3, the highest SMY of \(0.35\pm 0.02\) m\({}^{3}\) kg\({}^{-1}\)VS was measured for the variety \"Zubr\" from the harvesting time H2 (BBCH-codes 55-59), while the highest AMY value of \(5968.90\pm 82.70\) m\({}^{3}\) ha\({}^{-1}\) was determined for the variety \"Favoryt\" harvested at H3 (BBCH-code 61). For sorghum from Western European countries (Germany), specific methane yields between 0.263 and 0.328 m\({}^{3}\) kg\({}^{-1}\)VS are reported [10; 43]; for Southern European countries (Italy, Spain), the SMY varied between 0.240 and 0.386 m\({}^{3}\) kg\({}^{-1}\)VS [25; 45]. For German sorghum, areal methane yields of between 2900 and 3722 m\({}^{3}\) ha\({}^{-1}\) can be achieved [43]. The results of these investigations on the specific methane yields are in the middle range of those values for the Southern European countries. The maximal results of the areal methane yields determined for Ukrainian sorghum were higher than those values for German sorghum.