Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 10, 2001
Publication Date: December 20, 2001
Citation: DUNN, R.O. ALTERNATIVE JET FUELS FROM VEGETABLE OILS. TRANSACTIONS OF THE AMERICAN SOCIETY OF AGRICULTURAL ENGINEERS. 2001. Interpretive Summary: Air quality standards set forth by the Clean Air Act and its amendments have established guidelines for reduction of harmful ground level emissions from the aviation sector. Biodiesel, defined as the mono- alkyl esters of fatty acids derived from vegetable oil or animal fat, may have a beneficial effect on these emissions when employed as a fuel extender for combustion in jet turbine engines. This work examines fuel properties of soybean oil based biodiesel/jet fuel (BioJet) blends formulated with up to 30 percent by volume biodiesel. Viscosities, flash points, and water reactivities (an important characteristic of jet fuels for military applications) of BioJet blends were comparable to those of neat jet fuels. Although cold flow properties were more problematic, increased processing of biodiesel before blending showed that BioJet blends can match similar characteristics neat jet fuels. These results are important because they demonstrate that with adequate processing, BioJet blends will meet most of the stringent jet fuel specifications, leading to the conclusion that routine aircraft operations will not be limited by the biodiesel extender. These results will also be employed in development of jet engine performance and emissions testing as well as operations testing in aircraft fueled by BioJet blends.
Technical Abstract: Air quality standards set forth by the Clean Air Act and its amendments have established guidelines for reduction of harmful ground level emissions from the aviation sector. Biodiesel, defined as the mono- alkyl esters of fatty acids derived from vegetable oil or animal fat, in application as an extender for combustion in compression ignition (diesel) engines has demonstrated a number of promising characteristics including reduction of exhaust emissions. This work examines the feasibility of blending methyl soyate (SME) esters in 0.10-0.30 vol. frac. blends with JP-8 and JP-8+100 fuels. Testing of cold flow properties indicated that blends with as little as 0.10 vol. frac. SME may limit operation of aircraft at lower altitudes where ambient temperature remains warmer than -30 deg C. Treatment of SME with cold flow improver additives may decrease this limit by up to 9 deg C. Blending with winterized SME gave the best results, reducing the limit to as low as -47 deg C, a value that meets the standard fuel specification for JP-8. Water reactivity studies indicated that SME/JP-8 blends did absorb very little water from buffered solution following contact with the oil phase. Although interface ratings for blends with up to 0.50 vol. frac. SME were "1b" (clear bubbles covering not more than 50 % of the interface) or better, separation ratings were not in excess of "(3)" due to formation of cloudy suspensions in the oil layer. Although fatty derivatives such as biodiesel will undergo oxidative degradation more readily than jet fuels, careful production, transport, and storage of BioJet blends should not present a significant problem.