Contents lists available at ScienceDirect Industrial Crops & Products journal homepage: www.elsevier.com/locate/indcrop Production of fatty acid ethyl esters from rubber seed oil in hydrodynamic cavitation reactor: Study of reaction parameters and some fuel properties Olusegun D. Samuel a, ⁎ , Modestus O. Okwu a , Semiu T. Amosun b , Tikendra Nath Verma c , Sunday A. Afolalu d a Department of Mechanical Engineering, Federal University of Petroleum Resources, Effurun, Delta State, P.M.B 1221, Nigeria b Department of Mechanical Engineering, Yaba College of Technology, Lagos State, Nigeria c Department of Mechanical Engineering, National Institute of Technology, Manipur, 795004, India d Department of Mechanical Engineering Covenant University Ota, Ogun-State, Nigeria ARTICLE INFO Keywords: Rubber seed oil Transesterifcation Optimization Cavitation ABSTRACT The attributes of environmental balance, lower exhaust emission and renewability have made ethylic biodiesel production a preferable technique to methylic biodiesel production from inedible lipid oil. Hydrodynamic ca- vitation reactor (HCR), in particular has engaged a global interest due to its fexibility and desirable biodiesel properties. For the frst time, the study adopted HCR to produce ethyl esters (biodiesel) from low FFA rubber seed oil (RSO). The efects of transesterifcation variables namely catalyst dosage (KOH) (3–5 wt.%), reaction time (30–50 min) and ethanol/RSO molar ratio (3.5 7.0) were examined on the biodiesel yield. The yield of rubber seed oil ethyl ester (RSOEE) (92.5%) was the highest at the ethanol/oil molar ratio of 6/1, KOH of 4.5 wt. % and reaction time of 40 min. The cavitational yield for RSOEE production in the cavitation reactor was 4.13 g/ J. The fuel properties of the RSO ethyl esters synthesized from the HCR were within the ranges of the ASTM D6751 and EN 14214 specifcations. However, the oxidation stability (OS) did not comply with the standards. To further improve the low OS, the antioxidant can be included in the RSOEE to enhance the OS to an acceptable limit (> 6 h). Therefore, the HCR can be a feasible reactor for the production of cleaner and renewable fuel from various feedstocks. 1. Introduction In recent years, researchers are compelled to search for alternative fuel due to the rapid depletion of global petroleum reserves, unsteady and high cost of fossil fuel, and devastating consequence on the en- vironment (Samuel and Gulum, 2018; Shrivastava and Verma, 2019). Biodiesel is one of the best palliative measures to combat global warming associated with the fossil diesel. Production of biodiesel en- tails transesterifcation of oil with an alcohol in the presence of an appropriate catalyst, resulting in the fatty acid alkyl ester/biodiesel and formation of glycerol (Vijayaraghavan and Hemanathan, 2009; Purandaradas et al., 2018). Not quite long, biodiesel has been gaining attention as a result of technical benefts over fossil fuel such as (i) higher biodegradability, (ii) lower exhaust emissions, (iii) enhanced cetane number and fash point, (iv) improved lubricity and (v) negli- gible sulphur content (Medeiros et al., 2014; Phankosol et al., 2014; Pullen and Saeed, 2014). Researchers (Humphrey et al., 2017; Rathore and Madras, 2007; Atabani et al., 2013; Samuel, 2016; Rajak and Verma, 2018a, b; Rajak and Verma, 2019) reported that biodiesel can be produced from edible oils (soya bean oil, corn oil, groundnut oil, palm oil, and sunfower oil) and non-edible oils (animal fat, waste ve- getable oil, jatropha oil, algae oil, Spirulina microalgae and castor oil). The use of edible oils has almost been a concern as it stresses food utilization and afects its availability (Farm Energy, 2015; Wang et al., 2012; Tabatabaei et al., 2015). Amongst the oils, rubber seed oil (RSO) has appeared appealing for biodiesel production and observed to have comparable fuel properties with fossil diesel (Morshed et al., 2011; Onoji et al., 2016a; Ikwuagwu et al., 2000; Jose et al., 2011). In ad- dition, literatures (Omorogbe et al., 2013; Onoji et al., 2017a,b Kumar and Purushothaman, 2010; Gimbun et al., 2012; Aarathi et al., 2019) indicate feasibility of biodiesel production from rubber seed oil. Rubber tress (Hevea brasiliensis) emanated from the family of Euphorbiaceous are abundant in Venezuela, Ecuador, Colombia, Peru, Bolivia and Nigeria (Schultes, 1990; Onoji et al., 2016b; Muhammad et al., 2017). Long time ago, rubber seed production was documented to be 42,980 t in Nigeria (Ramadhas et al., 2005a). The researchers further https://doi.org/10.1016/j.indcrop.2019.111658 Received 31 January 2019; Received in revised form 24 July 2019; Accepted 8 August 2019 ⁎ Corresponding author. E-mail address: samuel.david@fupre.edu.ng (O.D. Samuel). Industrial Crops & Products 141 (2019) 111658 0926-6690/ © 2019 Elsevier B.V. All rights reserved. T