|Knothe, Gerhard - Gary|
Submitted to: Fuel
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/8/2008
Publication Date: 1/6/2009
Citation: Krahl, J., Knothe, G.H., Munack, A., Ruschel, Y., Schroder, O., Hallier, E., Westphal, G., Bunger, J. 2009. Comparison of Exhaust Emissions and Their Mutagenicity from the Combustion of Biodiesel, Vegetable Oil, Gas-to-Liquid and Petrodiesel Fuels. Fuel. 88:1064-1069. Interpretive Summary: Biodiesel is an alternative diesel fuel derived from vegetable oils such as soybean or canola (rapeseed) oil or other sources such as animal fats and waste frying oils. The chemical reaction of a vegetable oil or an animal fat with chemical compound known as alcohols gives biodiesel. The resulting materials are also known as fatty acid alkyl esters. Biodiesel and the fatty acid alkyl esters comprising it have different properties than the parent vegetable oils or animal fats. These differences are also reflected in the combustion in an engine, which leads to differences in the exhaust emissions. In this work, the mutagenic effects of exhaust emissions from biodiesel derived from canola-type rapeseed oil, its parent oil, conventional diesel fuel and a synthetic diesel fuel were compared. It was found that the exhaust emissions from the parent oil showed the by far strongest mutagenic effects. The other fuels were largely comparable among each other. The levels of individual exhaust emissions were also determined and were in line with prior results. This research shows that, when comparing exhaust emissions, biodiesel possesses advantages in terms of certain health effects in comparison to vegetable oils as fuels and that biodiesel is similar in this respect to modern clean petroleum-derived diesel fuels. Thus, biodiesel is a full replacement for petrodiesel fuels also in this respect.
Technical Abstract: Diesel engine emissions (DEE) are classified as probably carcinogenic to humans. In recent years every effort has been made to reduce DEE and their content of carcinogenic and mutanegnic polycycluc aromatic hydrocarbons (PAH). In several studies conducted since 1995, we observed an appreciable reduction of PAH emissions and mutagenicity of DEE caused by reformulated or newly developed fuels. The use of rapeseed oil as fuel is rapidly growing in German transportation businesses and agriculture due to economic reasons. We compared the mutagenic effects of DEE from rapeseed oil (RSO) with those of DEE from rapeseed methyl ester (RME, biodiesel), natural gas derived synthetic fuel (gas-to-liquid, GTL), and reference petrodiesel fuel (DF). The test engine was a heavy-duty truck engine operated on the European Stationary Cycle (ESC). The mutagenicity of the particle extracts and the condensates was tested using the Salmonella typhimurium/mammalian microsome assay with tester strains TA98 and TA100. Regulated exhaust emissions, total hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides (NOx), and particulate matter (PM) were also determined. The RSO particle extracts increased the mutagenic effects by factors of 9.7 up to 17 in tester strain TA98 and of 5.4 up to 6.4 in tester strain TA100 compared with the reference DF. The condensates of the RSO fuels caused up to three times stronger mutagenicity than the reference fuel. RME extracts had a moderate but significantly higher mutagenic response in assays of TA 98 with metabolic activation and TA 100 without metabolic activation. GTL samples did not differ significantly from DF. Regulated emissions remained below the limits except for an increase of up to 15% in NOx exhaust emissions from the tested biofuels.