## 3 Results and Discussion
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{3}{*}{**Source of Variation**} & \multirow{3}{*}{**Df**} & \multicolumn{6}{c}{**Element**} \\ \cline{3-10}  & & \multicolumn{2}{c}{**Cd**} & \multicolumn{2}{c}{**Cr**} & \multicolumn{2}{c}{**Cu**} & \multicolumn{2}{c}{**Fe**} \\ \cline{3-10}  & & **F** & _p_**-Value** & **F** & _p_**-Value** & **F** & _p_**-Value** \\ \hline B & 5 & 397.99 & \(<\)0.001 & 14,612.49 & \(<\)0.001 & 82,647.67 & \(<\)0.001 & 22,833.15 & \(<\)0.001 \\ T & 5 & 3323.72 & \(<\)0.001 & 17,895.24 & \(<\)0.001 & 9560.88 & \(<\)0.001 & 22,962.55 & \(<\)0.001 \\ BxT & 25 & 88.62 & \(<\)0.001 & 340.49 & \(<\)0.001 & 808.88 & \(<\)0.001 & 791.78 & \(<\)0.001 \\ \hline \multirow{3}{*}{**Source of Variation**} & \multirow{3}{*}{**Df**} & \multicolumn{2}{c}{**Ni**} & \multicolumn{2}{c}{**Pb**} & \multicolumn{2}{c}{**Zn**} \\ \cline{3-10}  & & **F** & _p_**-Value** & **F** & _p_**-Value** & **F** & _p_**-Value** \\ \hline B & 5 & 24735.82 & \(<\)0.001 & 2778.71 & \(<\)0.001 & 8245.12 & \(<\)0.001 \\ T & 5 & 7187.77 & \(<\)0.001 & 4464.35 & \(<\)0.001 & 6640.38 & \(<\)0.001 \\ BxT & 25 & 360.09 & \(<\)0.001 & 95.06 & \(<\)0.001 & 326.44 & \(<\)0.001 \\ \hline \hline \end{tabular}  
* Df is the number of degrees of freedom, F is the value of statistics F (statistics F of Fisher).  
\end{table} 
Table 1: Results of two-factor analysis of variance (two-way ANOVA) for biomass (B), temperature (T) and biomass and temperature interaction (BxT). \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Biomass**} & **Cd** & **Cr** & **Cu** & **Fe** & **Ni** & **Pb** & **Zn** \\ \cline{2-7}  & & & & **ppm** & & & \\ \hline Miscant & 4.98 & 34.12 & 56.07 & 3474 & 18.86 & 7.51  & 503.50 \\ Oak & 5.23 & 42.24 & 250.61 & 3050 & 53.06 & 8.75 & 141.93 \\ Pine & 5.60  & 37.25 & 145.38 & 3188 & 47.84 & 9.41 & 265.05 \\ Sunflower husk & 5.93 & 67.76 & 284.50 & 3681 & 76.11 & 5.10 & 277.96 \\ Wheat straw & 4.30 & 50.23 & 54.36 & 3647 & 31.11 & 5.93 & 212.67 \\ Willow & 5.61  & 61.46 & 140.18 & 1238 & 97.92 & 7.56  & 601.39 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Results of detailed comparisons of average content of individual trace elements in the tested biomass with the Tukey test at the significance level of 0.05. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Temperature**} & **Cd** & **Cr** & **Cu** & **Fe** & **Ni** & **Pb** & **Zn** \\ \hline \({}^{\circ}\)**C** & & & & **ppm** & & & \\ \hline
500 & 7.81 & 31.54 & 198.22 & 4386 & 34.38 & 10.06 & 558.44 \\
600 & 6.45 & 38.73 & 184.08 & 3647 & 40.96 & 9.13 & 445.50 \\
700 & 5.65 & 44.29 & 158.69 & 3308 & 50.65 & 7.90 & 381.17 \\
800 & 4.49 & 48.60 & 146.64 & 2773 & 55.73 & 7.01 & 283.27 \\
900 & 3.84 & 55.51 & 134.54 & 2304 & 67.22 & 5.36 & 218.54 \\
1000 & 3.40 & 74.38 & 108.94 & 1858 & 75.94 & 4.80 & 115.58 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Means for the determined temperatures. homogeneous (not significantly different) means were obtained for various elements. The key results presented in Table 4 are discussed below. Comparing the average Cd content, a division into groups of means that did not significantly differ in similar or the same temperatures was obtained, e.g., the means obtained at the temperature of 1000 \({}^{\circ}\)C for different materials (marked a). These are the smallest means. Another homogeneous group are the means (marked with the letter b) corresponding to miscant and temperature 900 \({}^{\circ}\)C, oak and temperature 1000 \({}^{\circ}\)C, pine and temperature 1000 \({}^{\circ}\)C, sunflower husk incinated at temperatures 900 and 1000 \({}^{\circ}\)C, wheat straw at temperatures 900 and 1000 \({}^{\circ}\)C as well as willow and temperature 1000 \({}^{\circ}\)C. Sunflower husk at 500 \({}^{\circ}\)C and wheat straw at 500 \({}^{\circ}\)C were significantly different from the other means (there are no letters denoting homogeneous groups).