Submitted to: Journal Oleo Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 20, 2001
Publication Date: May 20, 2001
Citation: DUNN, R.O., KNOTHE, G.H. ALTERNATIVE DIESEL FUELS FROM VEGETABLE OILS AND ANIMAL FATS. JOURNAL OLEO SCIENCE. 2001. Interpretive Summary: This report updates recent progress on improving the fuel properties of biodiesel, an alternative diesel fuel made from vegetable oils or animal fats. Processing was developed for modifying the flow properties of biodiesel during cold weather. With adequate processing, biodiesel may be produced with cold flow properties that match or exceed those of some conventional diesel fuels. Additives have also been developed that improve combustion quality of biodiesel such that harmful exhaust emissions such as nitrogen oxides may be reduced. This work is important because improving cold flow properties and reducing nitrogen oxides are two of the most significant technological problems that must be solved before more widespread commercialization of biodiesel is possible.
Technical Abstract: Biodiesel, defined as the mono-alkyl esters of fatty acids derived from vegetable oils or animal fats, is a strong candidate alternative fuel for combustion in compression ignition (diesel) engines. With respect to petroleum middle distillates (petro-diesel), biodiesel has superior cetane number and lubricity characteristics, has comparable heats of combustion and kinematic viscosities, and is non-flammable making it safer to store and handle. Biodiesel is renewable and can help reduce dependence upon imported petroleum. Biodiesel is environmentally friendly because it is readily biodegradable and its combustion reduces most harmful exhaust emissions, including carbon monoxide, unburned hydrocarbons, particulate matter, and polyaromatic hydrocarbons. In the United States, the Energy Policy Act (EPACT) of 1992 and Clean Air Act with its subsequent amendments have combined to help establish a favorable atmosphere for development of biodiesel; however, many technological hurdles must be removed before widespread commercialization will be feasible. During cooler weather, biodiesel "gels" at temperatures near freezing (0C) compared with temperatures in the range 15 to 17C for petro-diesel. Another concern for biodiesel is its long-term storage stability with respect to oxidative degradation. Finally, most research indicates that biodiesel does not significantly reduce nitrogen oxides (NOx) emissions. This is a particular concern because NOx may react in the atmosphere to form ozone, a component of smog. This work reviews recent progress in the development of biodiesel with emphasis on removing these technological hurdles.