## 3 Results and Discussion
### Characterization of Raw Materials for Energy Utilization
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{\begin{tabular}{c} **Fruit Species and** \\ **Characteristics** \\ \end{tabular} } & \begin{tabular}{c} **Moisture at** \\ **Collection** \\ **(wt. \%)** \\ \end{tabular} & \begin{tabular}{c} **Average** \\ **Particle Size** \\ **(mm)** \\ \end{tabular} & \begin{tabular}{c} **Ash** \\ **(wt. \%)** \\ \end{tabular} & \begin{tabular}{c} **HHV** \\ **(MJ\(\cdot\)kg\({}^{-1}\))** \\ \end{tabular} & \
\begin{tabular}{c} **LHV** \\ **(MJ\(\cdot\)kg\({}^{-1}\))** \\ \end{tabular} &
\begin{tabular}{c} **Bulk** \\ **Density** \\ **(kg\(\cdot\)m\({}^{-3}\))** \\ \end{tabular} \\ \hline Raspberry pomace & 19.6 & 0.8 & 4.8 \(\pm\) 0.2 \({}^{\text{d}}\) & 18.8 \(\pm\) 0.1 \({}^{\text{c}}\) & 15.79 \(\pm\) 0.07 \({}^{\text{cd}}\) & 486 \\ Sea-buckthorn pomace & 21.7 & 1.9 & 2.78 \(\pm\) 0.05 \({}^{\text{ab}}\) & 21.0 \(\pm\) 0.1 \({}^{\text{a}}\) & 17.82 \(\pm\) 0.17 \({}^{\text{a}}\) & 437 \\ Grape vine pomace & 36.2 & 2.7 & 2.8 \(\pm\) 0.6 \({}^{\text{ab}}\) & 20.4 \(\pm\) 0.5 \({}^{\text{a}}\) & 18.0 \(\pm\) 0.8 \({}^{\text{a}}\) & 496 \\ Grape vine seed cake & 8.0 & 67.4 & 3.5 \(\pm\) 0.6 \({}^{\text{bd}}\) & 20.84 \(\pm\) 0.15 \({}^{\text{a}}\) & 17.85 \(\pm\) 0.24 \({}^{\text{a}}\) & 1163 \\ Almond shell & 6.7 & 43.9 & 10.0 \(\pm\) 0.8 \({}^{\text{e}}\) & 17.51 \(\pm\) 0.04 \({}^{\text{b}}\) & 14.83 \(\pm\) 0.05 \({}^{\text{b}}\) & 362 \\ Pistachio shell & 4.7 & 19.3 & 2.07 \(\pm\) 0.12 \({}^{\text{ab}}\) & 17.23 \(\pm\) 0.03 \({}^{\text{b}}\) & 14.9 \(\pm\) 0.1 \({}^{\text{bc}}\) & 467 \\ Almond seed coat & 18.2 & 50.5 & 19 \(\pm\) 1 \({}^{\text{f}}\) & 20.49 \(\pm\) 0.04 \({}^{\text{a}}\) & 17.9 \(\pm\) 0.2 \({}^{\text{a}}\) & 512 \\ Peach stone & 9.7 & 39.4 & 0.51 \(\pm\) 0.01 \({}^{\text{c}}\) & 19.57 \(\pm\) 0.06 \({}^{\text{d}}\) & 17.14 \(\pm\) 0.15 \({}^{\text{f}}\) & 523 \\ Plum stone & 7.9 & 27.6 & 1.9 \(\pm\) 0.6 \({}^{\text{ac}}\) & 18.9 \(\pm\) 0.1 \({}^{\text{c}}\) & 16.05 \(\pm\) 0.24 \({}^{\text{de}}\) & 547 \\ Date stone & 17.4 & 30.7 & 1.47 \(\pm\) 0.04 \({}^{\text{ac}}\) & 17.75 \(\pm\) 0.04 \({}^{\text{b}}\) & 15.1 \(\pm\) 0.3 \({}^{\text{bc}}\) & 503 \\ \hline \hline \end{tabular} Note: Data are expressed as an average \(\pm\) standard deviation. Averages with different letters within the column are significantly different, according to [PERSON]’s test (\(p\leq 0.05\)).  
\end{table} 
Table 2: The physical and energy properties of materials. Most materials also meet the standard in terms of ash content, which is below 6% and belong to class A (family home use) [44]. Almond shell material is close to this limit but does not meet it, and thus and would be classified in the lower category B for industrial applications. The almond seed coat materials, on the other hand, have a significantly higher ash content and from this perspective are more suitable for co-firing with other materials [45]. The results confirmed that materials with lower ash content achieve higher HHV due to a higher calorific value. The combustion temperature in the boilers is also important for reducing ash and fuel emissions. The standard used for testing biofuels, ISO 18122 [26], defines a test temperature of only 550 \(\pm\) 10 \({}^{\circ}\)C, but the boiler combustion temperature is normally higher. Significant ash mass loss may occur at temperatures above 550 \({}^{\circ}\)C, and inorganic compounds decompose at temperatures above 750 \({}^{\circ}\)C [46]. Thus, even such materials as almond shells and seed coat can, in the end, produce lower ash content. In addition, higher ash content in itself may not be a problem, as it can be addressed by adjusting the combustion process and more frequent clearing of the fire grate in the boilers [47]. The materials evaluated in this work can be mostly processed very well for energy generation. A number of them (pistachio shell, peach, plum and date pits and grape seed cake) are suitable for incineration directly as they leave the processing lines.