ORIGINAL PAPER Fuel Properties of Biodiesel/Ultra-Low Sulfur Diesel (ULSD) Blends Robert O. Dunn Received: 13 October 2010 / Revised: 18 February 2011 / Accepted: 27 May 2011 / Published online: 17 June 2011 Ó AOCS (outside the USA) 2011 Abstract Biodiesel is an alternative fuel and fuel exten- der easily derived from vegetable oil or animal fat. In 2006, the US Environmental Protection Agency mandated that maximum sulfur content of diesel fuels be reduced to 15 ppm to protect catalysts employed in exhaust after- treatment devices. Processing to produce this ultra-low sulfur petrodiesel (ULSD) alters fuel lubricity, density, cold flow, viscosity, and other properties. Consequently, there is a need to develop a better understanding of the basic fuel properties of biodiesel/ULSD blends. This work evaluates the effects of biodiesel volumetric blend ratio (V BD ) on cloud point (CP), kinematic viscosity (m), specific gravity (SG), and refractive index (RI) of blends with petrodiesel. Properties measured for various blends of methyl esters of soybean oil (SME) and used cooking oil (UCOME) in ULSD were compared with those for blends with low sulfur (B500 ppm) petrodiesel fuel (LSD). With respect to increasing V BD , CP and SG increased and RI decreased with each parameter demonstrating a linear correlation. In contrast, m showed a curvilinear relationship with respect to increasing V BD . Calibration curves were derived from regression analyses to determine V BD in biodiesel/ULSD blends from measurements of each indi- vidual property. While the models had generally high coefficients of regression (R 2 [ 0.986), SG models were most accurate for predicting V BD to within 1.3 vol%. Keywords Biodiesel  Blend ratio  Cloud point  Refractive index  Specific gravity  Kinematic viscosity Introduction Biodiesel is a renewable alternative fuel made primarily from transesterification of plant oils or animal fats with methanol or ethanol. The National Biodiesel Board esti- mates that 700 million gallons (1 US gallon is approx. 3.79 liters) of biodiesel were produced in the US in 2008 [1]. Biodiesel has been applied to fuel transportation trucks, farm and other off-road vehicles, automobiles, locomotives, air- craft, stationary power generators, boilers, and heaters. Biodiesel possesses many characteristics that make it attractive as an alternative fuel for conventional diesel (petrodiesel). It is readily biodegradable, non-toxic, and non-flammable making it easier to store and handle. Gross heats of combustion, specific gravity (SG), and viscosity are comparable to those properties of petrodiesel. Biodiesel is miscible with petrodiesel and enhances cetane number, lubricity, and anti-wear properties [2–6]. It can be applied as a fuel component where its volumetric ratio (V BD ) is above 20 vol% (B20), an extender (V BD B B20) or an additive (V BD B B5) in blends with petrodiesel. Biodiesel reduces exhaust emissions with respect to smoke opacity, hydrocarbons, carbon monoxide, sulfur dioxide, polyaro- matic hydrocarbons, and particulate matter [2, 3, 5, 7]. Blends with biodiesel may increase nitrogen oxides (NOx) emissions, though increases do not exceed 5% for V BD up to B20 [7]. A recent ‘‘well-to-wheel’’ life-cycle analysis reported that biodiesel has an energy output/fossil energy Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the US Department of Agriculture. USDA is an equal opportunity provider and employer. R. O. Dunn (&) Bio-Oils Research, United States Department of Agriculture (USDA), Agricultural Research Service (ARS), National Center for Agricultural Utilization Research, Peoria, IL, USA e-mail: Robert.Dunn@ars.usda.gov 123 J Am Oil Chem Soc (2011) 88:1977–1987 DOI 10.1007/s11746-011-1871-3