In a study published in Archives of Toxicology, the team compared the mutagenic effects of emissions produced by two different batches of straight rapeseed oil to the emissions produced by rapeseed methyl ester (biodiesel), GTL diesel and a reference diesel fuel.

A German team of researchers has found that straight rapeseed vegetable oil used as a fuel in diesel engines shows a strong increase in the mutagenicity of emissions compared to a reference diesel fuel and other fuels.

The test engine was a heavy-duty diesel running the European Stationary Cycle. Particulate matter was sampled onto filters and extracted. Gas phase constituents were sampled as condensates. The mutagenicity of the particle extracts and the condensates was tested using the Salmonella typhimurium/mammalian microsome assay with tester strains TA98 and TA100.

Compared to DF [diesel fuel] the two RSO [rapeseed oil] qualities significantly increased the mutagenic effects of the particle extracts by factors of 9.7 up to 59 in tester strain TA98 and of 5.4 up to 22.3 in tester strain TA100, respectively. The condensates of the RSO fuels caused an up to factor 13.5 stronger mutagenicity than the reference fuel. RME [rapeseed methyl ester—biodiesel] extracts had a moderate but significant higher mutagenic response in assays of TA98 with metabolic activation and TA100 without metabolic activation. GTL [gas-to-liquids] samples did not differ significantly from DF.

In conclusion, the strong increase of mutagenicity using RSO as diesel fuel compared to the reference DF and other fuels causes deep concern on future usage of this biologic resource as a replacement of established diesel fuels.

Based on experimentation, the researchers concluded that the result does not result from the higher viscosity of straight vegetable oil compared to biodiesel and other fuels.

Whereas the legally limited emissions like carbon monoxide, hydrocarbons, particulate matter, and nitrogen oxides of RSO differed from the other fuels tested only in acceptable margins, the mutagenic effects were unexpectedly strong.

Compared to modern fossil fuels (DF, GTL), biofuels can produce similarly low emissions of mutagenic compounds (RME) but may also have strong contrary effects (RSO, mRSO). In general, a systematic research concerning the influence of fuels on the exhaust composition of diesel (and gasoline) engines is urgently needed in order to develop fuels with lower emissions of hazardous substances.

(A hat-tip to blomo!)

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