Preparation and fuel properties of field pennycress (Thiaspi arvense) seed oil ethyl esters and blends with ultralow-sulfur diesel fuel

Field pennycress (Thlaspi arvense L.) is a widely distributed winter annual with high seed oil content (36%) and is suitable as an off-season rotational crop in the Midwestern U.S. Erucic [(13Z)-docosenoic] acid (36.2%) is the most abundant constituent in the oil, with unsaturated and very long chain (20+ carbons) fatty acids comprising most of the remaining content. In a previous study, we described field pennycress seed oil methyl esters (FPMEs). Here, we report field pennycress seed oil ethyl esters (FPEEs) along with the properties of blends of FPMEs and FPEEs (B2-B20) in petrodiesel. These results are compared to American and European biodiesel and petrodiesel fuel standards. FPEE were characterized by excellent low temperature properties (cloud point -15 deg C), high cetane number (61.4), high kinematic viscosity (5.65 mm2/s), and low oxidative stability (induction period of 4.6 h). Both kinematic viscosity and oxidative stability did not meet EN 14214 limits but were within the ranges prescribed in ASTM D6751. With regard to blends, highly linear correlations (R2 = 0.99) were noted between blend ratio and density, energy content, kinematic viscosity, moisture content, and specific gravity. The acid value, sulfur content, and surface tension were essentially unaffected by the blend ratio. Oxidative stability was negatively affected by a higher biodiesel content, which is typical for blends. Cold flow properties were minimally impacted by the blend ratio, thus representing a significant advantage of FPMEs and FPEEs over other biodiesel fuels. Both FPMEs and FPEEs were excellent lubricity enhancers, because even small amounts (B2) markedly improved the lubricity of petrodiesel. Where applicable, fuel properties of the blends were within the limits prescribed in the petrodiesel standards.