## 3 Results and Discussion
### Cost Feasibility of Ultrasonic-Assisted Solvent Soil Washing  
This study was performed at a lab-scale level. In larger remediation scales, the energy cost remains a concern. For a volume of between 3500 and 4000 litter, ultrasonic cleaner and industrial stirrer (mixer) \begin{table}
\begin{tabular}{c c c c} \hline
**Category** & **Compounds** & **Formula** & **Concentration (mg/L)** \\ \hline Alcohol(s) & Ethanol & C2H6O & 3,071.00 \\  & 1-Propanethiol & C3H8S & 719.41 \\ Acid(s) & 2-Hexynoic acid & C6H9O2 & 435.20 \\  & Boric acid & H3 BO3 & 449.40 \\  & Ethanolio acid & C2H2O4 & 94.90 \\  & Formic acid & CH2O2 & 72.50 \\  & Propanoic acid & C3H6O2 & 103.90 \\ Aldehyde(s) & Acetaldehyde & C2H2O & 182.90 \\ Ketone(s) & 2-Butanone, (2,4-dinitrophenyl) hydrazone & C10H18N4O4 & 79.40 \\ Ester(s) & Diethyl ester & C4H10O & 94.90 \\ \hline \end{tabular}
\end{table} 
Table 1: Identified biosurfactant ingredients from the sugarcane wine. \begin{table}
\begin{tabular}{c c c c} \hline
**Category** & **Compounds** & **Formula** & **Concentration (mg/L)** \\ \hline Alcohol(s) & Ethanol & C2H6O & 1499.20 \\  & Ledene alcohol & C15H24O & 382.00 \\  & 2-Propanol, 1-chloro & C3H7 ClO & 485.20 \\ Acid(s) & 2-Pyrazincerboxylic acid & C5H4N2O2 & 307.20 \\  & 2-Methylpyrazine-5-carboxylic acid & C6H6N2O2 & 290.03 \\  & Pyrrolidine-1-thiocarbosylic acid & C11H5N5 & 167.00 \\  & Benzenesulfifolia acid & C7H7N3 & 193.00 \\  & 2-Pyrrolidinone & C4H5 NO & 363.00 \\  & 2-Amino-4-hydroxyteridine-6-carboxylic acid & C7H5N5O3 & 172.00 \\  & 1H-Purine-6-sulfonamide & C5H5N5O2 & 217.60 \\ Aldehyde(s) & 2-ethyl crotonic aldehyde & C2H6O & 253.00 \\ Ester(s) & 2-octyanoic acid, methyl ester & C9H14O2 & 205.20 \\  & Ethyl acetate & C4H8O2 & 210.00 \\  & (2,3-Butadienyloxy)benzene & C10H10O & 218.00 \\ \hline \end{tabular}
\end{table} 
Table 2: Identified biosurfactant ingredients from the pineapple wine. can cost about 4 and 5 kW per hour of operation, respectively. Since the electricity unit price in Taiwan is 0.13 USD/kWh, the total electricity cost of washing a volume between 3500 and 4000 litter can be 1.18 USD/h, resulting in a cost of 7.08 USD for six hours (washing cycles). As the electricity cost is minimal, the cost of the soil washing would strongly depend on the solvent. Tropical Asian countries like Vietnam, Thailand, and Taiwan have a large amount of sugarcane and pineapple farming to provide raw materials for wine and confectionery production. In fact, although there could be some variations between areas and seasons, the price for one litter of sugarcane wine or pineapple wine in those mentioned countries varies between 1 and 8 USD, while the price for industrial-grade ethanol fluctuates from 50 to 100 USD/litter. However, although our study used the newly-made wine, the field-scale remediation taking wine as a washing solvent can take advantage of materials from winery wastes, and leftovers of the wine and confectionery production, which also contain a high amount of alcoholic and other organic biosurfatants [39]. The use of leftovers for soil washing could help reduce the remediation cost. Besides, during the distillation/purification stage of the wine-making process, high molecular-weight volatile organic compounds (SVOCs) were collected and removed as residues although they, together with the light molecular-weight VOCs, may well be beneficial for the washing removal of organic contaminants. Therefore, future applications of sugary/winery leftovers in washing contaminated soil are suggested, using one before the purification stage or one which is less purified so that the heavy alcoholic products are not removed and can contribute to improving the washing efficiency and reducing the overall cost. Additionally, the traditional winery fermentation technique can be applied to ferment recycled food wastes to produce surfactant-rich compost tea for similar soil washing applications, which could improve the removal efficiency (therefore reduce the number of washing cycles) and thus will be covered in our future studies.