Comparison of exhaust emissions and their mutagenicity from the combustion of biodiesel, vegetable oil, gas-to-liquid and petrodiesel fuels Jürgen Krahl a , Gerhard Knothe b, * , Axel Munack c , Yvonne Ruschel c , Olaf Schröder c , Ernst Hallier d , Götz Westphal e , Jürgen Bünger e a Coburg University of Applied Sciences, 96406 Coburg, Germany b National Center for Agricultural Utilization Research, United States Department of Agriculture, 1815 N. University St., Peoria, IL 61604, USA c Johann Heinrich von Thünen-Institut, Federal Research Institute for Rural Areas, Forestry and Fisheries, 38116 Braunschweig, Germany d Institute of Occupational and Social Medicine, Georg-August-University of Göttingen, 37073 Göttingen, Germany e BGFA – Research Institute of Occupational Medicine, German Social Accident Insurance, University of Bochum, 44789 Bochum, Germany article info Article history: Received 6 August 2008 Received in revised form 30 October 2008 Accepted 8 November 2008 Available online 6 December 2008 Keywords: Biodiesel Diesel exhaust emissions Diesel fuel Mutagenicity Vegetable oil abstract Efforts are under way to reduce diesel engine emissions (DEE) and their content of carcinogenic and mutagenic polycyclic aromatic hydrocarbons (PAH). Previously, we observed reduced PAH emissions and DEE mutagenicity caused by reformulated or newly developed fuels. The use of rapeseed oil as die- sel engine fuel is growing in German transportation businesses and agriculture. We now compared the mutagenic effects of DEE from rapeseed oil (RSO), rapeseed methyl ester (RME, biodiesel), natural gas- derived synthetic fuel (gas-to-liquid, GTL), and a reference petrodiesel fuel (DF) generated by a heavy- duty truck diesel engine using the European Stationary Cycle. Mutagenicity of the particle extracts and the condensates was tested using the Salmonella typhimurium mammalian microsome assay with strains TA98 and TA100. The RSO particle extracts increased the mutagenic effects by factors of 9.7 up to 17 in strain TA98 and of 5.4 up to 6.4 in strain TA100 compared with the reference DF. The RSO condensates caused up to three times stronger mutagenicity than the reference fuel. RME extracts had a moderate but significantly higher mutagenic response in assays of TA98 with metabolic activa- tion and TA100 without metabolic activation. GTL samples did not differ significantly from DF. Regu- lated emissions (hydrocarbons, carbon monoxide, nitrogen oxides (NO x ), and particulate matter) remained below the limits except for an increase in NO x exhaust emissions of up to 15% from the tested biofuels. Published by Elsevier Ltd. 1. Introduction The replacement of petroleum-derived fuels by biogenic fuels from renewable resources has become of worldwide interest and is being researched for its environmental costs and benefits [1,2]. The reduction of atmospheric greenhouse gas (GHG) is especially important and is being addressed. The combustion of vegetable oil-derived fuels reduces net GHG emissions in comparison to pet- rodiesel [3]. However, less attention has been paid to possible hu- man health hazards [4–7]. Fatty acid methyl esters (FAME) or, more generally, fatty acid al- kyl esters, are proven as a suitable alternative to fossil diesel fuel (DF) producing similar or even lower emissions [8,9]. They are called biodiesel and are produced from various oil plants, e.g., rape- seed (canola), palm, soybean, sunflower and others. Biodiesel is produced by transesterification of vegetable oil with methanol or another alcohol [8,9], resulting in a fuel with properties similar to mineral oil-derived fuels. Diesel engine emissions (DEE) contain mutagenic and carcino- genic polycyclic aromatic hydrocarbons (PAH) on the surface of the emitted particles and – to a lesser amount – in the gaseous phase [10]. The formation of PAH depends on the type of engine, the engine load, fuel composition, and the effectiveness of exhaust after treatment. The influence of different fuels, including rapeseed methyl ester (RME) and soybean methyl ester (SME), on the muta- genic activity of DEE was demonstrated in previous studies [11– 18]. Generally, lower mutagenic activity was observed for the DEE generated by biodiesel than petrodiesel fuels. However, lower inflammatory potential was also found petrodiesel particulate matter (PM) than for biodiesel PM when tested on a transformed human epithelial cell line [19]. Recently, economic aspects have led to the increased use of crude unmodified rapeseed oil as fuel is in the German transporta- tion sector, although unmodified vegetable oils have been reported to cause engine deposits due to their higher viscosity [20]. 0016-2361/$ - see front matter Published by Elsevier Ltd. doi:10.1016/j.fuel.2008.11.015 * Corresponding author. E-mail address: gerhard.knothe@ars.usda.gov (G. Knothe). Fuel 88 (2009) 1064–1069 Contents lists available at ScienceDirect Fuel journal homepage: www.elsevier.com/locate/fuel