## 1 Introduction
Existing environmental impact studies of biofuels derived from oleaginous feedstocks have mainly focused on biodiesel, such as life cycle analysis of biodiesel production [28], comparative life cycle assessment of diesel production from crude palm oil and waste cooking oil via pyrolysis [29], comparative life cycle assessment of alternative strategies for energy recovery from used cooking oil [30], substitutable biodiesel feedstocks for the U.K. [31], and the used-cooking-oil-to-b biodiesel chain in Europe [32]. Furthermore, some authors have studied the combustion emissions of transesterified WCO, mainly in automotive sources, such as the effects of fuel injection pressure on the performance and emissions of a diesel engine fueled with waste cooking oil biodiesel-diesel blends [33], butyl-b biodiesel production from waste cooking oil, and fuel properties and emission performance [34], among others. As shown, although some research has been conducted on the environmental impacts and emissions performance of oleaginous derived fuels, few authors have addressed these issues from the perspective of its straight use as a fuel (non-transesterified) in fixed sources for electricity production [35; 36]. In addition, converting waste streams such as waste edible oil into valuable resources represents a three-win solution, dealing simultaneously with human security, pollution, and energy recovery [37]. Circular Economy (CE) is an emerging alternative concept to a traditional linear economy (make, use, dispose) in which resources are kept in use for as long as possible, extracting the maximum value from them whilst in use, and recovering and regenerating products and materials at the end of each service life [38]. The use of waste flows as an energy source is complementary to CE principles [39]. As in the case of most islands, electricity generation in the Galapagos Islands is heavily based on fossil fuels. According to its energy balance, 89% of the electricity produced in the islands comes from fossil fuels, 8.2% from wind, 2.5% from solar, and 0.1% from biofuels [40]. According to [PERSON] et al. [41], to progressively replace fossil-based energy in Ecuador, other types of non-conventional renewable technologies such as biomass (solid, liquid, and gas) must be developed. Galapagos has endured severe environmental and economic impacts from fossil fuel spills on its marine reserve. The most serious was caused by a spill from a tanker in 2001, at San Cristobal Island. A total of 662,447 L of diesel and fuel oil was spilt into the sea. This disaster triggered the decision to foster renewable energy implementation in the islands. In this context, \"The Zero Fossil Fuels\" initiative was adopted [42]. One component of this project is a biofuel program that aims to reduce the environmental footprint attributed to fossil fuel usage through partial replacement with vegetable oils. In addition, the risks associated with fossil fuel transportation from the mainland to the islands could also be addressed. The biodegradation rate of oleaginous biofuels is 80.4%-91.2% after 30 days, while fossil diesel only reaches 24.5% biodegradation during the same period [43]. Floreana Island is the smallest (172.29 km\({}^{2}\)) of the inhabited islands of the Galapagos archipelago. It is located 1000 km from Continental Ecuador [44]. Since 2010, the biofuel pilot program has operated on the island using pure _Jatropha curcas_ oil as an energy source in three dual electricity generators which can work indiscriminately with 100% diesel, 100% pure vegetable oil, or any proportion of blends among those. The thermoelectrical group produces 256,713 kWh per year [40]. The current electricity generation by source in Galapagos is shown in Table 1.  
The biofuel program also seeks to reach other islands in the future. The estimated biofuel demand for a B20 blend (20% biofuel/80% diesel) for the San Cristobal and Isabela islands is 585,964.4 and 268,003.2 L of biofuel per year, respectively [45].