Engine performance of biodiesel fuel prepared from soybean soapstock: A high quality renewable fuel produced from a waste feedstock

A previously-developed bench-scale method for the production of fatty acid methyl esters (biodiesel) from soybean soapstock (Haas, M. J.; Bloomer, S.; Scott, K. J. Am. Oil Chem. Soc. 2000, 77, 373-379) was taken to the small pilot scale, producing approximately 2.5 L of material per run. By multiple successive reactions, 25 L of product was accumulated. The fatty acid comp osition of the ester product (wt %) was palmitic: 16.2, stearic: 4.7, oleic : 16.2, linoleic: 54.4, and linolenic: 6.9. This mirrors the fatty acid com position of soy soapstock and is quite similar to that of commercial biodie sel produced from refined soybean oil. The ester product met the provisiona l biodiesel specifications of the American Society for Testing and Material s with regard to all variables examined: flash point, water and sediment, c arbon residue, sulfated ash, density, kinematic viscosity, sulfur, cetane n umber, cloud point, copper corrosion, acid number, free glycerin, and total glycerin, and had density and iodine number values comparable to those of commercial soy-based biodiesel. Emissions data for both the neat fuel and a 20 vol % blend in low-sulfur petroleum diesel were collected according to the Environmental Protection Agency heavy-duty transient cycle protocol usi ng a DDC Series 60 engine on an engine test stand. The emissions profile of biodiesel from soapstock was quite similar to that of biodiesel produced f rom refined soy oil. Compared with petroleum diesel fuel, emissions,of tota l hydrocarbons, particulates, and carbon monoxide were reduced 55%, 53%, an d 48%, respectively, with neat soapstock biodiesel. Total nitrogen oxides i ncreased 9%. Operation on a 20 vol % blend of soapstock biodiesel in petrol eum diesel gave reductions of 27.7%, 19.7%, and 2.4%, respectively, in tota l hydrocarbons, particulate matter, and carbon monoxide, relative to petrol eum diesel. Nitrogen oxide emissions increased 1.3%. In the context of engi ne emissions, these data suggest the suitability of the methyl esters of so y soapstock as a diesel fuel.