## 3 Results and Discussion
### Elemental Analysis  
Distillation stillage has a nitrogen content of 2.57%, which is slightly higher than the 2.494% found in wine pomace (Table 4). The carbon content of distillation stillage is 54.928%, which is greater than the 52.099% in wine pomace. Carbon content is directly related to the calorific value of the biomass; thus, distillation stillage has a higher potential energy output due to its higher carbon percentage [44; 45]. Hydrogen content, another critical factor for energy release during combustion, is 6.725% in distillation stillage, which is higher than the 5.669% in wine pomace [45]. This indicates that distillation stillage may have a higher energy release potential. Sulfur content in distillation stillage is 0.153%, which is significantly higher than the 0.043% found in wine pomace. Lower sulfur content in wine pomace suggests it is more environmentally friendly, as it would result in fewer SOx emissions during combustion [44]. The oxygen content is 31.862% for distillation stillage and 33.337% for wine pomace. Lower oxygen content generally correlates with higher calorific value, implying that distillation stillage might have a slightly higher energy density compared to wine pomace [44; 45]. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sample** & **Moisture (\%)** & **Volatile Matter (\%)** & **Ash (\%)** & **Fixed Carbon (\%)** \\ \hline Distillation stillage & 5.454 \(\pm\) 0.118 & 58.97 \(\pm\) 0.265 & 3.762 \(\pm\) 0.129 & 31.813 \(\pm\) 0.018 \\ Wine pomace & 5.268 \(\pm\) 0.027 & 62.695 \(\pm\) 0.057 & 6.359 \(\pm\) 0.038 & 25.677 \(\pm\) 0.093 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Proximate Analysis of distillation stillage and wine pomace (dry basis). Comparing these results with the findings from [43], grape stalks contained 48.1% carbon, 5.8% hydrogen, 1.3% nitrogen, 0.4% sulfur, and 44.4% oxygen. Grape pomace had 53.5% carbon, 5.7% hydrogen, 2.5% nitrogen, 0.1% sulfur, and 38.2% oxygen. This distillation stillage's higher carbon and hydrogen contents suggest a higher potential calorific value, consistent with the trends observed in [43], where higher elemental carbon and hydrogen correlate with higher energy output. The \(t\)-test results from the elemental analysis reveal that statistically significant differences are observed in carbon (\(p\)-value equal to 0.00242), hydrogen (\(p\)-value equal to 0.00951), and sulfur content (\(p\)-value equal to 0.0171) between the two materials. Nevertheless, there is no significant difference in nitrogen (\(p\)-value equal to 0.707) content, and the difference in oxygen content (\(p\)-value equal to 0.0964) is not statistically significant. This indicates that while the materials differ significantly in several elemental compositions, nitrogen and oxygen contents do not. In summary, both distillation stillage and wine pomace show promise for energy recovery. Distillation stillage has advantages with lower ash content and higher fixed carbon, suggesting more efficient combustion with less residue. This makes it well-suited for direct combustion and pyrolysis processes, which convert the organic material into bio-oil, syngas, and biochar through high-temperature treatments. These processes benefit from the high energy density of distillation stillage, resulting in efficient energy recovery [46]. Wine pomace, with higher volatile matter content, may offer a quicker and more intense initial energy release but, often requires pretreatment to enhance its energy potential due to its lower carbon content and higher levels of nitrogen and sulfur. Enzymatic hydrolysis is commonly used to break down the complex carbohydrates in wine pomace into fermentable sugars, which can then be converted into bioethanol through microbial fermentation. This biological treatment process is advantageous as it operates under milder conditions compared to thermal methods, reducing energy input and preserving the structural integrity of the biomass.