## 2 Materials and Methods
### Environmental Conditions  
Provided that the containers were located outdoors and in order to evaluate the effect of environmental conditions, a daily measurement for temperature, humidity, wind speed and amount of rainfall was carried out during the entire experimental period of six months, which was averaged on a monthly basis (Table S1 in the supplementary material). These parameters were studied since relevant information can be obtained regarding the changes that can occur in the odorant compounds due to the exposure time and the climate variability related to the rainfall and the temperatures as the year progresses from winter to spring. In any case, the influence of the environmental conditions on the samples in the study was found to be similar to that already reported by [PERSON] et al. [10]. This study was performed for samples of the same type of wastes and exposed to environmental conditions in the same location but performed in the year prior to this current study, concluding that the key factor in the change of the properties of the waste is the environmental temperature followed by the rain to a lesser extent. Representative samples were extracted every month for a six-month period from each container containing alperujo and orujo waste as described elsewhere [10]. Every month, subsamples from different parts of the container of each residue were mixed independently in a 50 L polypropylene container and manually stirred to obtain a final homogeneous sample. These mixtures of orujo and alperujo were separated every month as follows: 5.0 kg frozen at \(-18\)\({}^{\circ}\)C stored as control samples; 1.0 kg for laboratory tests in triplicate, using standardized methods according to DIN [12] and AOAC International [13] and 15.0 kg of orujo and alperujo samples that were divided into three subsamples of 5.0 kg each to be dried in the drying trommel in triplicate. Table 1 shows the main characteristics of the physical-chemical parameters analyzed of each waste prior to its drying phase. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Month**} & \multicolumn{2}{c}{**Moisture Content (\% wb)**} & \multicolumn{2}{c}{**Ashes (\% wb)**} & \multicolumn{2}{c}{**Measuring Heating Value**} \\  & **Oven Method—AOAC** & \multicolumn{2}{c}{**Muffle Method—AOAC**} & \multicolumn{2}{c}{**(MJ kg\({}^{-1}\))**} * \\  & **945.15** & \multicolumn{2}{c}{**940.26**} & \multicolumn{2}{c}{**Norm DIN Serie 51.900**} \\ \hline  & **Alperujo** & **Orujo** & **Alperujo** & **Orujo** & **Alperujo** & **Orujo** \\ \hline
**Jul** & 77.7 \(\pm\) 0.1 & 79.5 \(\pm\) 0.2 & 2.4 \(\pm\) 0.1 & 3.2 \(\pm\) 0.1 & 22.3 \(\pm\) 0.1 & 22.4 \(\pm\) 0.2 \\
**Aug** & 77.9 \(\pm\) 0.5 & 80.2 \(\pm\) 0.3 & 2.2 \(\pm\) 0.1 & 3.1 \(\pm\) 0.1 & 22.1 \(\pm\) 0.2 & 22.4 \(\pm\) 0.1 \\
**Sept** & 80.0 \(\pm\) 0.5 & 81.8 \(\pm\) 0.4 & 1.9 \(\pm\) 0.2 & 2.9 \(\pm\) 0.1 & 22.4 \(\pm\) 0.1 & 22.5 \(\pm\) 0.1 \\
**Oct** & 73.1 \(\pm\) 0.2 & 77.4 \(\pm\) 0.2 & 1.6 \(\pm\) 0.1 & 2.7 \(\pm\) 0.1 & 22.2 \(\pm\) 0.1 & 22.4 \(\pm\) 0.2 \\
**Nov** & 60.5 \(\pm\) 0.4 & 63.4 \(\pm\) 0.2 & 1.6 \(\pm\) 0.1 & 2.2 \(\pm\) 0.1 & 22.1 \(\pm\) 0.1 & 22.6 \(\pm\) 0.2 \\
**Dec** & 53.0 \(\pm\) 1.0 & 55.4 \(\pm\) 0.4 & 1.2 \(\pm\) 0.2 & 2.0 \(\pm\) 0.1 & 22.3 \(\pm\) 0.1 & 22.7 \(\pm\) 0.2 \\ \hline \hline \end{tabular}  
* Dry basis; ** wet basis.  
\end{table} 
Table 1: Results of the physical-chemical analysis for samples of alperujo and orujo corresponding to the initial conditions before processing in the drying trommel over time. Deviations correspond to the standard deviation of triplicates. Each month, alperujo and orujo samples were introduced in triplicate in a pilot-scale rotary drying trommel shown in Figure 1. The drying trommel consisted mainly of a turbo-heater (2) of propane-butane gas (model SG30) with a direct flame that provides the caloric energy to the system.