## 3 Results and Discussion  
### Biodiesel and Biolubricant Characterization  
The FAME profile of WCOBD after the first transesterification of WCO is shown in Figure 2. As observed, methyl linolenate is the main FAME, accounting for 66.8%, followed by methyl oleate (22.3%), palmitate (3.9%), linolenate (3.0%), and stearate (2.9%). Other studies included similar FAME profiles, with the main composition differences related to the two main FAMEs (that is, methyl linoleate and oleate) [41; 47]. This could be due to the fact that WCO composition depends on the culinary traditions of each area or circumstance; apparently, sunflower oil prevailed in this study (at the expense of olive oil) as the typical vegetable oil in this region. A typical chromatogram was obtained in this case (as reported in previous works), with high peak resolution, which allowed the quantification of each kind of FAME [60]. As explained in the literature, the fatty acid profile of the vegetable oil (and the subsequent FAME profile for biodiesel and ester profile for the corresponding biolubricant) will play a central role in biodiesel and biolubricant characteristics [14; 61]. Table 5 shows the main characteristics, for this study, of biodiesel and biolubricant obtained from WCO. Figure 2: FAME profile of WCOBD. The term “others” includes minor FAMEs. Firstly, the suitability of most WCOBD properties should be noted, according to the standard (including CFPP in hot climates, which was 1 \({}^{\circ}\)C in this case) [33], except for oxidation stability, which is below the upper limit (8 h). This could be on account of the fact that the FAME profile had high quantities of methyl linoleicate, which is a di-unsaturated component. Thus, double bonds are usually the starting point for auto-oxidation processes due to free-radical generation, and the presence of saturated or mono-unsaturated FAMEs (such as methyl palmitate and oleate, respectively) is desirable [15]. On the other hand, WCOBL presented a high viscosity at 40 \({}^{\circ}\)C, with viscosity at 100 \({}^{\circ}\)C of 11.24 cSt and a viscosity index of 173, which implies low changes in viscosity with temperature (a desirable property for industrial purposes). In this case, acidity increased compared to WCOBD possibly due to the additional heat treatment carried out for biolubricant production, with the possible degradation of the sample and the subsequent release of free fatty acids [62]. Additionally, the high flash and fire points found in this case should be noted, which ensure safety during storage and handling. Again, as in the case of WCOBD, WCOBL showed low oxidation stability (exceeding 2.5 h), due to the presence of linoleic acid in the original WCO, thereby transferring its instability to this final product. In this sense, both biodiesel and biolubricant obtained from WCO required the addition of antioxidants to improve oxidation stability and the subsequent quality maintenance during storage or oxidation, as explained in further subsections. Regarding WCOBL, its phytotoxicity applied to lettuce was assessed, including the main results in Figures 3 and 4. Firstly, visual degradation of control samples was clear on Days 3 and 7 (due to the lack of watering since Day 0), with slight differences shown compared to samples watered with WCOBL (25% and 50%), which were more degraded (especially concerning turgor and yellowing of leaves). Figure 3: Phytotoxicity test of FOBL addition. \begin{table}
\begin{tabular}{l c c} \hline \hline
**Property** & **WCOBD** & **WCOBL** \\ \hline Viscosity at 40 \({}^{\circ}\)C, cSt & 4.50 & 62.89 \\ Density, kg\(\cdot\)m\({}^{-3}\) & 881 & 904 \\ Yield, \% & 98.9 & 90.18 \\ Acid value, mgKOH\(\cdot\)g\({}^{-1}\) & 0.22 & 0.55 \\ Iodine value, g\({}_{2}\)\(\cdot\)100 g\({}^{-1}\) & 98 & Not determined \\ Oxidation stability, h & 1.28 & 2.63 \\ Flash and fire points, \({}^{\circ}\)C & 173–179 & 242–249 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: WCOBD and WCOBL characterization.