## 3 Results and Discussion  
Among all the samples extracted from the exhaust gases during alperujo and orujo drying and later analyzed by TD-GC/MS, more than 600 compounds were identified. However, a large list of them only appeared a few times or in small abundances, well below their odor threshold. In addition, the reliability of some identified compounds was below 98% coincidence with the NIST library [14]. Thus, inventory of all the compounds found over time was reduced to these shown in Table 3, in which VOCs were classified by families, including the months in which each VOC was detected during the course of the study. Only those compounds that were found in more than 25% of the 108 output samples were considered representative in terms of emissions, following the criteria described by [PERSON] et al. [15] for compost maturation emissions in a wastewater treatment plant. The compounds considered in the analysis have a ratio in the areas in comparison to the total area of the sample with an average of 63.62% for July to 92.95% for December, monotonously increasing as time passes. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Based Compound** & **Sample** & **Standard 1** & **Standard 2** & **Standard 3** \\ \hline Methanol & \(n\)-Hexane & 0.5 ppm\({}_{\text{v}}\) & 1.5 ppm\({}_{\text{v}}\) & 3.0 ppm\({}_{\text{v}}\) \\ Methanol & \(n\)-Octane & 0.5 ppm\({}_{\text{v}}\) & 1.5 ppm\({}_{\text{v}}\) & 3.0 ppm\({}_{\text{v}}\) \\ Methanol & \(n\)-Nonane & 0.5 ppm\({}_{\text{v}}\) & 2.0 ppm\({}_{\text{v}}\) & 5.0 ppm\({}_{\text{v}}\) \\ Methanol & D3710-95 & 0.5 ppm\({}_{\text{v}}\) & 1.0 ppm\({}_{\text{v}}\) & 2.5 ppm\({}_{\text{v}}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Concentration of the standard for the quantification of VOC concentrations. Table 3 shows that there are a significant number of compounds repeated over time for the samples of alperujo and orujo. Abundance is shown as 1-6, indicating that these compounds appeared in all the sampling events throughout the 6 months of experimentation, while those that appeared as a single number, for example 1, are those that only appeared in the first month (June) of experimentation. The compounds found more frequently (all months from 1 to 6) in both alperujo and orujo corresponded mainly to aldehydes (benzaldehyde, furfural and nonanal), alcohols (phenol, 2-furanmethanol), carboxylic acids (acetic acid) and hydrocarbons (toluene, hexane, octane and nonane). This leads to consider such molecules as target compounds for further treatment of emissions from the drying process. Consequently, these compounds were later selected for further quantification. Interestingly, [PERSON] et al. [9] showed that these types of molecules appear mostly when the temperature exceeds 150 \({}^{\circ}\)C because the process of thermal destruction of the wood hemicellulose begins. In addition, [PERSON] et al. [22] demonstrated that when the temperature in the rotary drying system increased from 60 \({}^{\circ}\)C to 250 \({}^{\circ}\)C in a time of 45 min for the drying of alfalfa, the presence of VOCs increased, especially hydrocarbons, alcohols, aldehydes and ketones. Thus, emissions are increased when the