# Assessment of Areal Methane Yields from Energy Crops in Ukraine, Best Practices
## 3 Results and Discussion
### Data Analysis for Maize, Sweet Sorghum and Miscanthus  
A generalized linear model procedure was used for the analysis of data based on the results for maize, sweet sorghum and miscanthus. Based on the modelling results, the following conclusions can be drawn:  
SMY was significantly affected by the BBCH-code (\(p\) = 0.0009) and by the variety (\(p\) < 0.0001). The highest SMY was determined for the analysed maize and sweet sorghum samples. The highest SMY values for the maize samples were related to the vegetation stage of wax to full ripeness (BBCH-codes [83, 84, 85, 86, 87]). For sweet sorghum, the highest SMY corresponded to the period between the mid-stage of inflorescence (earing) and the flowering stage (BBCH-codes [55, 56, 57, 58, 59, 60, 61]). For miscanthus, the highest SMY values were determined for the samples harvested at earlier harvesting times, which corresponded to the vegetation period between the stem elongation and booting (BBCH-codes [36, 37, 38, 39]).  
Figure 4: Specific methane yield (SMY) and areal methane yield (AMY) of the miscanthus varieties harvested at H1, H2 and H3 harvesting times, which correspond to a certain BBCH-code related to a specific stage of crop phenological development. The analysed varieties were: (1) Species Giant Chinese Silver Grass: _Miscanthus x giganteus [PERSON] ex [PERSON]_, the variety name “Osinnii zoretsvit”, referred to as “Giganteus”. (2) Species Chinese Silver Grass: _Miscanthus sinensis [PERSON]_, the variety name “Misiachnyi promin”, referred to as “Sinensis”. “Giganteus” from the 3 rd and the 8 th years of vegetation and “Sinensis” from the 3 rd vegetation year were analysed. Histograms are charted based on the mean values; error bars indicate the variability between the three replications. Lower case letters indicate significant differences between the analysed miscanthus samples according to the results of the Tukey test.  
AMY was significantly affected by the BBCH-code (\(p=0.0024\)) and by the variety (\(p<0.0001\)). The highest AMY among the three crops was found for miscanthus \"Ciganteus\" from the 8 th vegetation year harvested at H1 (\(7404.55\pm 199.00\) m\({}^{3}\) ha\({}^{-1}\), BBCH-code 36). For maize and sweet sorghum, the highest yields were found when collected at the third harvesting time. When harvested at H3, the mean AMY values for maize with the highest yields (\(4929.99\pm 1285.53\) m\({}^{3}\) ha\({}^{-1}\), BBCH-codes 87-89) have slightly overperformed those values for sweet sorghum (\(4767.17\pm 1125.41\) m\({}^{3}\) ha\({}^{-1}\), BBCH-codes 55-75). Thus, the AMY of miscanthus was about 50% higher than that of the traditional energy crops maize and sweet sorghum. Miscanthus has an additional advantage of being a perennial crop, which can be cultivated for more than 20 years; moreover, this crop can be grown on marginal and contaminated lands for soil phytoremediation [16; 47]. Furthermore, the cultivation costs for miscanthus are lower, than those for maize and sweet sorghum. In further studies, SMY and AMY of miscanthus under other vegetation years up to the death of plantation have to be further investigated.