# Biodiesel and Biolubricant Production from Waste Cooking Oil: Transesterification Reactor Modeling
## 3 Results and Discussion
### Industrial Equipment, Reactor Design, and Economic Feasibility Study
#### 3.5.4 Economic Feasibility Study  
Once the main components of the chemical plant for biolubricant production from WCO were established, a preliminary economic study was conducted to assess the feasibility of the implementation of this kind of facility. The costs of the products were determined according to the location established in this work and described in Section 3.5.1. Concerning the direct costs and according to the yearly demands of the plant, Table 13 shows the estimated costs of the reagents for the first and second transesterifications (the data were obtained from local and national distributors, and average values are presented). \begin{table}
\begin{tabular}{c c} \hline
**Parameter** & **Size** \\ \hline Reactor volume, m\({}^{3}\) & 3 \\ Reactor surface area, m\({}^{2}\) & 29.49 \\ Inner diameter, m & 1.563 \\ Height, m & 1.562 \\ Wall thickness, mm & 6 \\ Weight, kg & 168.53 \\ \hline \end{tabular}
\end{table} 
Table 11: Reactor size for WCO biodiesel and biolubricant production. \begin{table}
\begin{tabular}{c c c c c c} \hline
**D\({}_{a}\)** & **H** & **J** & **E** & **W** & **L** \\ \hline
0.521 & 1.563 & 0.130 & 0.521 & 0.104 & 0.130 \\ \hline \end{tabular}
\end{table} 
Table 12: Size of the stirring system (measurements are expressed in m). Also, the TBHQ addition should be considered. In this case, the addition of 300 ppm of TBHQ could be suitable to obtain at least 8 h of oxidation stability, according to the results observed in Figure 4, where 262 ppm of TBHQ assured an oxidation stability of 8 h, rounding up to 300 ppm to simplify the calculations in this case (assuming the minimum standard for biodiesel samples [43]). This way, assuming a total biolubricant production of 424,989.8 kilograms per year, 127,497 g of TBHQ would be necessary, with a total cost of 37,739.11 \(\upxi\) (at 29.60 \(\upxi\cdot\)g\({}^{-1}\)). As a result, the total cost related to raw materials was 150,808.43 \(\upxi\). Regarding staff costs, the results observed in Table 14 were based on national work agreements [62]. It should be noted that the salary and social charges (around 35% of each salary) are constantly changing, with the subsequent impact of this factor on the implementation of a plant with these characteristics. When it comes to energy costs, different stages were considered to assess the power required and the annual costs, as observed in Table 15. If an average value of 0.180 \(\upxi\cdot\)kWh\({}^{-1}\) is considered, according to several electric companies, the total annual cost of the plant would be above 5500 \(\upxi\). Also, machine costs should be considered in this preliminary study, as observed in Table 16. The total cost of the reactor (including the container and stirrer) was 69,380 \(\upxi\) \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Transesterification Process** & **Reagent** & **Price, \(\upxi\cdot\)T\({}^{-1}\)** & **Amount, \(\upxi\cdot\)y\({}^{-1}\)** & **Annual Cost, \(\upxi\cdot\)y\({}^{-1}\)** \\ \hline \multirow{4}{*}{First} & WCO & 82 & 435.12 & 35,679.84 \\  & CH\({}_{3}\)OH & 265 & 92.93 & 24,626.45 \\  & Sodium & \multirow{2}{*}{1800} & 13.05 & 23,490 \\  & methoxide & & 541.1 & 83,796.29 \\  & Total & \(-\) & 541.1 & 83,796.29 \\ \hline \multirow{4}{*}{Second} & TMP & 150 & 46.45 & 6967.5 \\  & Sodium & \multirow{2}{*}{1800} & 12.38 & 22,284 \\  & methoxide & & 58.83 & 29,251.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 13: Direct costs for WCO-based biodiesel and biolubricant production. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Job Post** & **Number of Workers** & **Salary** &
\begin{tabular}{c} **Total Salary +** \\ **Social Charges** \\ \end{tabular} \\ \hline Plant manager & 1 & 44,658.05 & 60,288.37 \\ Chemist & 1 & 28,985.65 & 39,130.63 \\ Qualified worker & 2 & 21,739.23 & 51,087.19 \\ Total & 4 & 95,382.93 & 150,506.19 \\ \hline \hline \end{tabular}
\end{table} 
Table 14: Staff costs for WCO-based biodiesel and biolubricant production.