## 4 Life Cycle Inventory Results
### WCO In Situ Production Inventory  
Waste cooking oil (WCO) is defined as an oil-based substance that has been used in cooking or food preparation and is no longer suitable for human consumption [79]. The disposal of large amounts of WCO has become a problematic issue in most countries. WCO cannot be discharged into drains or sewers because this will lead to blockages, odor, or vermin problems and may also pollute watercourses, causing problems to wildlife [80]. It is also a prohibited substance and will cause problems if dumped in municipal solid waste landfills or municipal sewage treatment plants [81]. When WCO reaches natural ecosystems, such as rivers, aquifers, or subsoil, the environmental consequences can be severe. In terms of economic and energy costs, the inappropriate disposal of used cooking oil represents 3 kWh and about 1\(\upmu\)F, respectively, per kg of WCO delivered to the sewer system [82]. These risks must be highlighted in a fragile ecosystem such as Galapagos Islands. Using WCO as an alternative fuel for energy generation could therefore be a sustainable solution not only for disposal but also for greenhouse gas (GHG) emission abatement. Many countries around the world, e.g., Portugal, Greece, Italy, Spain, Belgium, Denmark, China, U.S.A, Australia, Germany, the U.K., and Korea, have implemented regulations for using WCO \begin{table}
\begin{tabular}{c c c} \hline \hline
**Inputs/Outputs** & **Unit** & **Amount** \\ \hline \multicolumn{3}{c}{**Input**} \\ \hline RPO & kg & \(3.5\times 10^{2}\) \\ Lubricating oil & kg & 1.9 \\ Transport, truck \textless{} 10 t EURO1 & tkm & \(1.4\times 10^{2}\) \\ Marine transport 350 t ship & tkm & \(4.2\times 10^{2}\) \\ Heat and power co-generation unit, 50 kW electrical, components & P & \(7.7\times 10^{-4}\) \\ Sodium hypochlorite & kg & \(1.1\times 10^{-5}\) \\ Water & kg & \(1.8\times 10^{2}\) \\ \hline \multicolumn{3}{c}{**Outputs**} \\ \hline Carbon monoxide, biogenic & kg & \(2.3\times 10\) \\ Carbon dioxide, biogenic & kg & \(4.8\times 10^{2}\) \\ Hydrocarbons & kg & \(8.6\times 10\) \\ Electricity & MWh & \(1\) \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Inputs and outputs to produce 1 MWh from RPO. for energy [83]. Also, WCO could potentially be used as an in-situ-produced biofuel, reducing environmental and capital costs in line with circular economy principles. The use of this potential energy source would also reduce in a significant manner the environmental impact of fossil-fuel-based energy generation in islands. In this context, collecting and recycling WCO contributes to simultaneously solving three environmental problems: waste reduction by reuse/recovery, reduction of fossil fuel dependence, and reduction of pollutant emissions [84]. Furthermore, studies developed by [PERSON] (2018) showed advantages regarding the water footprint for WCO when compared with other biodiesel feedstocks, finding the lowest impact for WCO with 0.03 world m\({}^{2}\)eq/kg, while for palm oil, the results were 1.26 world m\({}^{2}\)eq/kg [85]. According to [PERSON] (2017) [35], the use of WCO in diesel engines is much more feasible for the stationary production of electrical and thermal energy; an illustrative example is the Vegawatt system developed by Owl Power Company in the U.S.A. which produces electricity in situ using WCO [86], and in low-speed diesel engines, i.e., those of large ships [87], rather than for automotive applications. In this last case, direct use of WCO on a large scale is currently not feasible due to the need for changes in the design of the engines, as well as for organization of the distribution network. A comparison of the physical and chemical properties of palm oil, WCO, and diesel is shown in Table 8.  
The diesel consumption for electricity generation in CARICOM's islands is 218 million liters per year or 8.4 M GJ [99].