Phytotoxicity of three plant-based biodiesels, unmodified castor oil, and Diesel fuel to alfalfa (Medicago sativa L.), lettuce (Lactuca sativa L.), radish (Raphanus sativus), and wheatgrass (Triticum aestivum) Ifeoluwa Bamgbose n , Todd A. Anderson The Institute of Environmental and Human Health (TIEHH), Department of Environmental Toxicology, Texas Tech University,1207 Gilbert Drive Box 41163, Lubbock, TX 79409-1163, USA article info Article history: Received 16 April 2015 Received in revised form 5 August 2015 Accepted 6 August 2015 Keywords: Biodiesel Diesel Plant Soil Contamination Phytotoxicity Germination abstract The wide use of plant-based oils and their derivatives, in particular biodiesel, have increased extensively over the past decade to help alleviate demand for petroleum products and improve the greenhouse gas emissions profile of the transportation sector. Biodiesel is regarded as a clean burning alternative fuel produced from livestock feeds and various vegetable oils. Although in theory these animal and/or plant derived fuels should have less environmental impact in soil based on their simplified composition re- lative to Diesel, they pose an environmental risk like Diesel at high concentrations when disposed. The aim of the present study was to ascertain the phytotoxicity of three different plant-derived biodiesels relative to conventional Diesel. For phytotoxicological analysis, we used seeds of four crop plants, Medicago sativa, Lactuca sativa, Raphanus sativus, and Triticum aestivum to analyze the germination of seeds in contaminated soil samples. The toxicological experiment was conducted with two different soil textures: sandy loam soil and silt loam soil. The studied plant-based biodiesels were safflower methyl- ester, castor methyl ester, and castor ethyl-ester. Biodiesel toxicity was more evident at high con- centrations, affecting the germination and survival of small-seeded plants to a greater extent. Tolerance of plants to the biodiesels varied between plant species and soil textures. With the exception of R. sativus, all plant species were affected and exhibited some sensitivity to the fuels, such as delayed seedling emergence and slow germination (average ¼10 days) at high soil concentrations (0.85% for Diesel and 1.76% for the biodiesels). Tolerance of plants to soil contamination had a species-specific nature, and on average, decreased in the following order: Raphanus sativus (0–20%) 4Triticum aestivum (10–40%) ZMedicago sativa 4 Lactuca sativa (80–100%). Thus, we conclude that there is some phytotoxicity as- sociated with plant-based biodiesels. Further, the findings of this study can be useful for selecting the least fuel-tolerant species as a soil contamination bio-indicator and for determining the risks of biodiesel contamination. & 2015 Elsevier Inc. All rights reserved. 1. Introduction The growing environmental concern of petroleum-derived pro- ducts contamination and degradation of ecosystems has spurred the search for alternative energy sources, such as biodiesel (Gashaw and Lakachew, 2014; Xue et al., 2011; Sharma and Singh, 2009). Its via- bility is mainly due to the fact that biodiesels are alkyl monoesters of fatty acids (Xue et al., 2011) produced from renewable biological sources such as straight plant (vegetable) oil, animal oil/fats (Xue et al., 2011; Moser 2011; Van Gerpen, 2005), or tallow and waste cooking oil (Strong et al., 2004; Ma and Hanna, 1999) through the transesterification process (Gashaw and Lakachew, 2014; Moser, 2011, Ma and Hanna, 1999). Biodiesel is widely favored because it is reported to be renewable (Xue et al., 2011), biodegradable (Vauh- konen et al., 2008; Knothe, 2005), non-flammable (Ma and Hanna, 1999; Von Wedel and Point Richmond, 1999), and less toxic in comparison to crude oil based Diesel fuels because it contains no sulfur (Moser, 2011; Von Wedel and Point Richmond, 1999) or aro- matics (Sharma and Singh, 2009; Strong et al., 2004; Von Wedel and Point Richmond, 1999), and has low greenhouse gas emission pro- files (Von Wedel and Point Richmond, 1999). Biodiesel is a fuel composed of monoalkyl esters of long-chain fatty acids derived from renewable vegetable oils or animal fats meeting the requirements of ASTM D6751 through a chemical pro- cess termed transesterification (Gashaw and Lakachew, 2014). This reaction involves a TAG reaction with a short-chain monohydric Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/ecoenv Ecotoxicology and Environmental Safety http://dx.doi.org/10.1016/j.ecoenv.2015.08.003 0147-6513/& 2015 Elsevier Inc. All rights reserved. n Corresponding author. E-mail address: ait109@aol.com (I. Bamgbose). Ecotoxicology and Environmental Safety 122 (2015) 268–274