AQUEOUS SOLUBILITY, DISPERSIBILITY AND TOXICITY OF BIODIESELS

Abstract

ABSTRACT With increasing interest in the use of plant and animal oils as potential petroleum fuel replacements, there is the potential for accidental release of these biodiesels to the environment. While the behaviours and effects of petroleum diesels have been extensively studied, little is known about either the fate of biofuels in water or their potential effects on aquatic ecosystems. The most important mechanism for exposure of aquatic ecosystems to biodiesels and petroleum diesels is the transfer of material from the non-aqueous phase liquid (NAPL) into the aqueous phase, as both soluble and dispersed components. The equilibrium levels of fuel components in the water, the water-accommodated fractions (WAF) have been measured in fresh water for biodiesels from feedstocks of soy oil, canola oil, waste fry tallow and fish wastes. Biodiesel and petroleum diesels blends of 5% (B5) and 20% (B20) are also measured. Aqueous toxicities are also reported for pure biodiesels and petroleum diesel. Acute toxicities were assessed by 96-hour LC5os of Daphnia magna and rainbow trout and by IC5os of bioluminescent bacteria. The correlations between acute toxicity, WAF concentrations and fuel property data are examined. Natural and chemically-enhanced dispersion of biodiesel is examined in both low- and high-energy conditions. Biodiesels are found to have significant differences with petroleum diesels in water chemistries and in potential ecological impacts. All organisms tested show that biodiesels have less acute toxicity than petroleum diesels. Biodiesels and biodiesel-rich blends were found to be very much more dispersible in high-energy conditions than petroleum diesel.