Methylic and ethylic biodiesel production from crambe oil (Crambe abyssinica): New aspects for yield and oxidative stability Mateus Cristian Gomes Souza a , Marcelo Firmino de Oliveira b, * , Andressa Tironi Vieira a , Anízio Marcio de Faria a , Ant ^ onio Carlos Ferreira Batista a a Institute of Exact and Natural Sciences of Pontal, Federal University of Uberl^ andia, 38304-402, Ituiutaba, MG, Brazil b Department of Chemistry, Faculty of Philosophy, Sciences and Letters at Ribeir~ ao Preto, University of S~ ao Paulo, 14040-901, Ribeir~ ao Preto, SP, Brazil article info Article history: Received 22 July 2019 Received in revised form 7 July 2020 Accepted 14 August 2020 Keywords: Crambe oil Transesterification Biodiesel Degumming Oxidative stability abstract Biodiesel is a fuel comprised of mono-alkyl esters of long-chain fatty acids derived from vegetable oils or animal fats. Biodiesel is designated B100 and is regarded as the major substitute for fossil diesel. Crambe abyssinica, a native plant from Ethiopia, has great potential for biodiesel production due to its higher calorific value and oxidative stability as compared to soybean oil biodiesel. Compared to fossil diesel, C. abyssinica oil biodiesel emits significantly less CO 2 without efficiency loss. However, its crude oil only provides good results if it undergoes supercritical transesterification. Here, we aimed to produce ethyl and methyl esters from crambe oil under ambient conditions. Initially, we tested two methods to degum crambe oil: aqueous degumming and acid degumming. We subjected the degummed oil to trans- esterification through the methylic or the ethylic route, catalyzed by KOH. The methyl esters of the biodiesel obtained by esterification of crambe oil submitted to acid degumming had higher oxidative stability as compared to the methyl esters of the biodiesel obtained from crambe oil subjected to aqueous degumming: 15.7 h and 10.7 h, respectively, but the yield was lower: 70% vs. 80%, respectively. The ethyl esters of the biodiesel obtained from crambe oil submitted to aqueous degumming provided the highest yield and oxidative stability: 65% and 8.5 h, respectively. We also evaluated the oxidative stability of blends consisting of crambe oil methylic or ethylic biodiesel and soybean oil biodiesel. © 2020 Elsevier Ltd. All rights reserved. 1. Introduction Today, the impacts of global climate change are undoubtedly one of the most discussed topics. The technological and industrial challenges regarding measures that minimize the increasing at- mospheric concentrations of greenhouse gases are still the subject of intense debate [1]. In this scenario, developing new renewable energy sources is paramount. One example of a renewable energy source is biodiesel, a fuel produced from biomass. As an energy source, biomass offers many advantages, including a reduction in the number of greenhouse gases generated by fossil fuel burning. According to World Bank reviews, the use of bioethanol in the United States can potentially reduce total greenhouse gas emissions by up to 30%; in Brazil, this reduction could reach a significant 90% [2]. Methanol and ethanol are the alcohols that are mostly employed in biodiesel production [3]. Methanol is more often applied on a commercial scale for physical, chemical, and economic reasons: it is cheaper and more reactive than ethanol, which implies lower temperature and shorter reaction time [4]. According to the World Bank and The Royal Society, biofuel production has caused some problems: it has increased grain pri- ces, competition for water and land [5], deforestation and has en- dangered agrobiodiversity [6]. Therefore, research into new and nonfood raw materials is essential. A further challenge regarding biodiesel is the fact that its chemical characteristics make it very susceptible to oxidative processes, so it is less stable than fossil diesel [7]. Biodiesel oxidation occurs because the double bonds in the free fatty acid chains are highly reactive. Thus, the biodiesel oxidative stability is linked to its composition and varies according to the number of fatty acid unsaturation. Biodiesel oxidation takes place through three steps: initiation, propagation, and termination. Initiation is triggered when a free radical captures hydrogen from a carbon atom, to produce a carb- anion. In the presence of O 2 , a reaction happens rapidly, to give an * Corresponding author. E-mail address: marcelex@ffclrp.usp.br (M. Firmino de Oliveira). Contents lists available at ScienceDirect Renewable Energy journal homepage: www.elsevier.com/locate/renene https://doi.org/10.1016/j.renene.2020.08.073 0960-1481/© 2020 Elsevier Ltd. All rights reserved. Renewable Energy 163 (2021) 368e374