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German Researchers Find Straight Rapeseed Oil Fuel Increases Mutagenicity of Diesel Engine Emissions

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.

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.

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!)



Rafael Seidl

Mutagenicity is typically demonstrated on lab rats. Other studies have shown that the mutagenic effects of high doses of PM from regular DF did not carry over to other animal species, raising doubts about the relevance of the rat-based studies for human population health. I`m not an ocologist, merely passing along what I have heard and read.

In purely technical terms, straight or waste vegetable oil presents other problems: additional DF tank needed for cold starts and the initial phase of cold weather driving; modifications sometimes needed to avoid accumulated damage to fuel pump, injectors and turbocharger; modifications typically needed to reduce PM emissions to regulated levels. On the up side, SVO/WVO and any biodiesel produced from it is naturally free of sulfur, which greatly aggravates the negative health impact of all PM in which it is present as sulfuric acid.

The main attraction of SVO/WVO is of course the low cost, especially given the ease of (illegal) fuel tax evasion. It`s possible that both the oil industry and the finance ministries have a vested financial interest in supporting research that undermines SVO/WVO use. However, research such as that referenced in the article is peer reviewed, so someone will have to actually disprove it rather than just dismiss it out of hand.


Well, that sucks. Is nothing sacred? Talk about taking the "green" out of green fuels.

Harvey D.

Anybody knowns who financed this research?


Let's put this in perspective. Burning any hydrocarbon releases harmful emissions. There are any number of emissions which we know are toxic but still don't regulate (at least in transportation): PAHs, aldehydes, ketones, peroxyacyl nitrates ... but we live with them anyway, even as we are told to stay indoors during smog alerts. There is a study out there noting that diesel PM is more carcinogenic than gasoline PM while gasoline PM does more genetic damage than diesel PM (nice choice) ... our response is to complain about being stuck in traffic. Nearly all metropolitan areas are in exceedence of ozone limits several times a year, sometimes weeks at a time, and our response is to crank up the AC and make sure we drive everywhere 'cause we sure wouldn't want to be outside breathing the stuff. We all know that CO2 is a train wreck waiting to happen and our response is to blame the evil oil cos and complain about the price of gas.

We are stuck with the ICE for the short and medium term. There are no great options here, air quality and climate-wise, but the least bad are BTL and FAE biodiesels, now that ULSD finally enables DPFs and NOx scrubbing. BTL better than FAE in direct emissions, life cycle analysis maybe, maybe not. But we have to be careful about feedstock. And we can't make enough of either (or any other alternative) to satisfy our current consumption, so neither is a magic bullet.


There are other one about the holy Diesel:

Here is a link to the group that did the research:


Natural does not mean non-toxic, OK? So we do the research and figure out how to make it better. Or maybe don't use canola oil?

This is what R & D of a new fuel infrastructure looks like. And it's also a perfect illustration why government shouldn't pick fuels or technologies to subsidize.

While sometimes it may shed light on the relevance of a study, the "who paid for the research" question does not automatically invalidate the results. It gets used so often these days that it's approaching a logical fallacy. We still have to be objective about putting results into perspective. The more important question than "who paid for it?" is "can it be duplicated?"

We need to proceed slowly and carefully into biofuels, and NO ONE has a crystal ball.


Here is your link to Big Bad Oil, Automotive and RME for our spin-off, Harvey ;) :

But then there's still that traditional smell to SVO-tailpipes, you know...
Ladies and gentlemen, please let's try to not start behaving like olive green fried Libertarians and other geeks defending their evasion strategies against 'eco-fascists', their altruistic greenness against US-imperialism and what else they're prepared for with all the weapons of counterconspirations they can reach for... (here in Germany since doubt arose)

We should already know lots more about alternative emissions by now, so those dottores are plain right in asking research - the primary interest they may be suspect of.

To diesel engine emissions there's more than a few dead rats, like tissue testing or epidemiological research. We can't afford to play off CO2 against classic emissions.
The sooner the clarifications, the less harm, private misinvestment, counterproductive subsidies and time lost.
Oil seeds based fuels will hardly be considered acceptable in the future, with their deficits upstream, but anyway personally I'd like to see more systematic research efforts around the effects of all the proposed fuels that might clean up long living vehicles that won't be replaced by HCCIs, fuel cells and the like.
Dimethyl carbonate, DME, biobutanol, even methanol...


It would also appear that the usage path for biofuels calls for blends in the foreseeable as no manufacturer is about to endorse SVO. SVO issues of wear, viscosity, cold start are pretty well known. How 'bout these studies look at practical fuel blends B5, 10, 50, etc.

Just because BioWillie has been a big success it is no reason to think as Raphael says:

"It`s possible that both the oil industry and the finance ministries have a vested financial interest in supporting research that undermines SVO/WVO use."

Or is it?

Harvey D.

PHEVs with very quick charge, higher capacity battery packs could reduce fuel consumption by 85% or more and may be a much better solution.

Using our farms to grow feedstocks for fuel does not sound like the proper think to do.
More people would starve as food production is reduced.

However, transforming unwanted polluting wastes (all kinds) into useful fuel (specially gaz) has merits. Wastes gasification may eventually produce enough energy (gas fired power plants) to charge (many/most of) our PHEV batteries.

aussie paul

This is another reason why biofuels are becoming a humanitarian and ecological disaster in their present form. There needs to be a freeze on the use of biofuels until they can be produced without using foodstuffs or without clearing forests. Bring on the PHEV's.

Where does the "juice" for the P come from. Im a big fan of wind turbines and solar cells too, but they only work when the wind blows or the sun shines, nor can they be relied upon during peak load. And some people drive more than an hour a day or night.

Can oil palms grow in deserts with irrigation?


Can anyone say ALGAE?


what's the surprise here ? ignorance of organic chemistry ?

there are 40 recognized mutagens & carcinogens
in the exhaust of ANY gas car, new, old or brand spanking new...the japanese recently published the finding of a new carcinogen in DF emissions 3x more potent than the previously most potent reported DF emissions carcinogen...biofuels combustion emissions science hasn't even started...

if there was irrigation, there would be no desert to start with ... irrigation from where ? peeing caravan camels ?


I dont know exactly, merely posing the ?. Marginal arid lands, windmills, PVs, desalinization of marginal water...get enough Caterpillars together and alot of crazy things can happen...doubtful on the peeing caravan camels though, but thanx for paying attention.


Some are saying that it may be easier to grow mustard seed as a feedstock for biodiesel rather than rapeseed or canola
However you wouldn't want to breathe the exhaust from an engine fuelled by raw mustard seed oil


archimedes wrote: what's the surprise here ? ignorance of organic chemistry ?

Exactly. Diesel particulates are particularly nasty in that they are small enough to evade the lungs mechanisms for removal of foreign objects. They can lodge in tissue, leaching concentrated mutagens in a small area. Face it, without expensive post-treatment, diesel sucks.

mo wrote: We can't afford to play off CO2 against classic emissions.

Like hell we can't! Not only can we, but we must. The only moral thing to do is to attempt to compute the least harmful path, subject to the price you wish to place on human life. We have epidemiological data telling us particulates kill tens of thousands of people yearly, and injure millions. I am not denying the possibility of harm from GW, but it is mostly in the future, difficult to accurately predict, and subject to mitigation. Compared to gas ICE and various other options, diesel does not look that great to me at the moment. Clean Diesel will of course change this, but the timeline for its widespread introduction is not much different than that of PHEVs.


Currently we are moving to new dedicated server where we are going to provide wide, interactive platform for energy, and climate issues enthusiasts and professionals. We are going to start as of 01.Junne 2007. You are all wellcome to live your comments, write articles, or simply pass by.


Can anyone put this in laymans terms for me? What I am understanding is that fossil fuels are reccomended by this study because of the capacity of vegetable oil emissions to mutate. What does in mutate into?

Alfred Meuser

A new study, maybe more neutral, released in July 2007 by the german bifa Umweltistitut Augsburg, says, that pure plant oil used as fuel in a vehicle using a suitable modification of the injection system has less mutagenicity than diesel.

Details of modification systems you can find on - see english summery.

Robert Northrup, Texas

This is a rather well-done experiment. I am a molecular biologist at the NSERL at UT Dallas. Although I have never done an emissions test before, an Ames mutageneity assay is standards. But this isn't the end of the road, kiddos.

First off, they only use rapeseed oil.
Second off, we don't know if it has been filtered at all. They mentioned a supplier co., gave us nothing further to go on.
Third of all, it is unclear which 2-tank system(s) they used, nor how the mRSO was heated, nor for how long.
Fourth of all, it is known that if SVO or WVO is not handled correctly, peroxides form, and fatty-free-acid (free radicals) - which would certainly mutate the hell out of some helpless Salmonella histidine operons.

Fifth of all, a company, Bioltec, has a system which was tested by BIFA and showed a reduction of mutageneity in Ames tests. It took me a long time to find the link, and unfortunately the paper is in German, not a language I speak, however as with all scientific papers, the figures are rather easily comprehended by anyone versed in the field (

My concern with this BIFA report, ironically, is that BIFA is not a university, and this report is not in the literature - not peer reviewed. It is sort of the inverse of an oil company's hired research firm. So until someone tests the bioltec system independently, it is suspect.

I am personally interested in their system, and wrote an email in broken German to see if they have an English-speaking agent I can deal with.

All that said, this paper should be taken seriously, and any sort of a priori notions that vegetable oil, because it comes from vegetables, cannot do harm - well, sorry. All the oil in the ground came from dinosaurs and microbes in the ocean (diatoms), albeit from deep in the mother earth. It all comes down to what we're doing with it.

Ulrich Weilnhammer

Dear Robert,

here are some information on your question:

The bifa insitute is a partly state owned research institut in Germany. The test were done at the Shell laboratories in Hamburg, the samples analyzed by the bifa institute. bioltec had no access to the samples at any time.

The bioltec-system is a 2-tank-system, which was the first worldwide that is (1) power-controlled (2) variable fuel management. I.e. the system detects fully automatically the operating status of the engine at each respective moment (temperature and acutal power) and gives the engine the appropriate fuel (Diesel for cold engine or idle mode oder low power) or plantoil (high / maximum power in hot engine). bioltec even can use defined and power-/temperature-dependent blends of both fuels.

bioltec has performed EURO5-emission tests with DaimlerChrysler, DAF, MAN, Iveco and Volvo. The results in brief: -45% particle emissions, -30% HC-emissions, -35% CO-emissions, NOx is within EURO5-threshold.

Mutagenity is reduced bei 50% per mg of particle-emission and by 75% (factor 4) per km / mile.

Testing results have been confirmed last week by another state institute (tfz Straubing).

I hope this information helps.


Theo. Stacy is a link to another study by one of the authors indicating particular problems with rapeseed oil's boiling point charecteristics = flat curve, thus problems with combustion.

"When comparing diesel fuel (DF) with RME, the disad-
vantage of RME becomes obvious: RME has almost one
boiling point, not a well rising boiling curve. An increas-
ing boiling curve is beneficial for a good fuel ignition and
combustion in the cylinder. Therefore RME may not be
considered as an optimal prospective fuel."

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