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Health Researchers Call for More Investigation into Possible Effects of Biodiesel Exhaust

10 January 2007

In an open access commentary published in Environmental Health Perspectives, researchers from University of North Carolina School of Public Health and the US EPA’s National Health and Environmental Effects Research Laboratory call for more research into the possible health effects of biodiesel exhaust.

While noting that using biodiesel fuel “is favorably viewed,” the authors also note that the suggestions that biodiesel exhaust is less likely to present risk to human health relative to petroleum diesel are speculative. Given the push for greater biodiesel use, they argue, the effects need to be more fully researched.

Currently there is a strong desire and need for an alternative fuels in this country. Employment of biodiesel fuel is favorably viewed and there are suggestions that its exhaust emissions are less likely to present any risk to human health relative to petroleum diesel emissions (Mauderly 1997). However, the speculative nature of a reduction in health effects based on chemical composition of biodiesel exhaust needs to be followed up with investigations using newer biological approaches gained from years of diesel research.

It is our opinion that biodiesel requires greater due diligence then it has received to date in the United States.

After reviewing the extant literature on biodiesel emissions, the authors recommend the study of a number of issues:

  • The consequences of biodiesel exhaust from blends.

  • The consequences of the use of additives. There are numerous additives to biodiesel, such as cetane improvers, smoke suppressors, flow enhancers, cloud-point depressors, wax anti-settling additives, detergents to reduce injector nozzle fouling, antioxidants for unsaturated oils, and controls for microbial growth. including Additives to biodiesel fuel are numerous and may impact human health. Some of these additives include metals. No emissions data are yet available for biodiesel combined with the additives required for practical application of biodiesel fuel usage on a national level.

  • The effect of disparate levels of aldehydes in biodiesel fuel and its exhaust emissions, which may be associated with varying impacts on indices of human health. Low quality biodiesel, which does not met high productions standards, will emit greater quantities of aldehydes due to poor post-transesterification refining. Biodiesel from some feedstock oils may have higher concentrations of aldehydes relative to those from others. It is unclear whether this might impact human health.

  • The affect of the new petroleum diesel engine combustion and after-treatment technologies, designed to decrease specific exhaust components such as particulate matter and nitrogen oxides.

  • The affect of the use of pesticides on plants with subsequent contamination of feedstocks.

(A hat-tip to Green Car Congress reader MR!)

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January 10, 2007 in Biodiesel | Permalink | Comments (17) | TrackBack (0)

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Researches call for more research, to be paid for by somebody else no doubt. I will take this type of PR seriously if the people announcing it also undertake to decline any offers of funding.

Undoubtedly this study can result in findings that show increased hazard to human health - if the funders find that to be expedient to their business.

Dr.med.J.Bruch, Univiersity Hospital Essen (Germany) and IBE GmbH, came to the following conclusions in 2005:

1. There is a lower bound for the airborne particulate concentration, below which no negative health effects can be demonstrated.

2. It is more important to reduce imissions of specific compounds and agglomerations with high carcinogenic potential than it is to reduce particulate concentrations across the board.

Note: certain hydrocarbons, especially polycyclic aromatics found in petrodiesel are known carcinogens and tend to attach themselves to soot agglomerations. The combustion of PCAs is even more complex than that of alkanes and, intermediary compounds include furanes and dioxins. Some but not all of these are toxic even in very low doses. Biodiesel does not contain PCAs, nor is it likely that any are formed during the combustion process. However, detailed knowledge of the chemical species produced during the combustion of all automotive fuels remains patchy.

3. On a scale of 0 (low risk, corund) to 4 (high risk, quartz dq12), diesel soot was found to rate approx. 1.

Note: at the time of publication, European on-road diesel contained up to 50ppm sulphur.

Source (in German): 26th Vienna Engine Symposium

http://www.övk.at/veranstaltungen/symposien/2005/nachlese/26.%20Int.%20Wiener%20%20Motorensymposium%202005.pdf

Apparently someone is pissed that biodiesel fuel “is favorably viewed.”
I read the Intro of the report. They ,Swanson, Madden and Ghio have got nothing. They're just soliciting for work.

These guys have a valid point. Biofuels are not a panacea -- burning them still emits C02 and many of the same toxic byproducts as fossil fuels.

Of course, the elephant in the room is still conservation. Driving to work on biodiesel is nice, but riding a bike is so much nicer.

Rafael Seidl posted: Biodiesel does not contain PCAs, nor is it likely that any are formed during the combustion process. However, detailed knowledge of the chemical species produced during the combustion of all automotive fuels remains patchy.

Upon what basis do they claim that PCAs (normally called Polynuclear Aromatic Hydrocarbons or PAHs) are unlikely to form during biodiesel combustion? It is my impression that PAH formation can occur in the combustion of nearly any carbonaceous fuel. The formation is disfavored by a very lean mixture. They admit that (their own?) detailed knowledge of speciation in combustion is "patchy", although they may not have talked to any combustion experts.

Biodiesel may be cleaner than petrodiesel, but it's still diesel, and as such is not as clean as gasoline.

A note to the science-bashers here: When scientists say "more research is needed", they are saying that they don't have all the answers. I find the claims that scientists are only in it for the money or are otherwise unethical to be offensive.

George:

The Lev II and Tier 2 bin 5 regs here require diesel exhaust in passenger vehicles to be as clean as gasoline.

George -

petrodiesel combustion produces lower engine-out PCA/PAH emissions than any gasoline engine, see e.g.

http://www.wrapair.org/APACE/SPECIATION/summary_topic3.htm

And that's considering that US petrodiesel contains a larger fraction of isomers, polyalkanes and aromatics than European petrodiesel does, because US refineries have to hydrocrack even valuable middle distillates to satisfy the demand for gasoline. The portion of the hydrocracking residue known as light cycle oil is mixed in to #2 diesel. This is why US diesel features lower cetane numbers than the European grade, i.e. it's harder to combust and tends to produce higher particulate emissions.

Biodiesel consists of fatty acid methyl esters. Can we be certain that the PM produced when combusting this fuel does not contain any PAHs or other carcinogenic compounds? No, the highly complex speciation of real-world diesel combustion processes is still too poorly understood. So by all means, let the scientists research this.

Note that European diesel vehicles have featured oxidation catalysts for over a decade and most new ones now feature a wall-flow DPF either standard or as an option. They will become standard on all cars when Euro 5 kicks in in 2010. What matters for population health is not engine-out but tailpipe emissions.

Cervus points out that in the US, the LDV diesels about to be released in or after 2008 will meet Tier 2 Bin 5, making their as clean as gasoline cars in the standardized drive cycle. This is possible only because the US has switched to ULSD, comparable to the 10ppm standard that will come into force in Europe in 2010 (though some countries' refineries already meet it today).

It would be unwise to assume a priori that these clean diesels will still pose a greater risk to population health than the vast majority of gasoline-powered vehicles do. On the contrary, establishing a modern clean diesel LDV fleet in the US will prompt refineries there to raise cetane levels, yielding a modest PM reduction even from legacy diesel vehicles.

The science of Diesel/Biodiesel emissions have one quality that is not accounted for in the public policy of the tailpipe.. the environment into which they are emmitted. Airshed's prone to cumulative aggregation, density of population exposed, demograph (and thus health) of those at risk, as well as specific at risk groups have to be taken into account(diabetics/asthmatics/imunocompromised/athletes etc.).

When these externalities are factored into the public health 'cummulative exposure' Biodiesel [B100] may well be prerequisite for best practice.

The 40 seater Bus I saw today ran the very close risk of my calling the fire brigade, if for no other reason to embarrase the operator. I had dialed the number on my cellphone but the operator was saved by another incompetant driver 'avoiding the smokescreen' causing me to prioritise safety. Emmissions carry risk's unrelated to the generic standards! Good injector maintenance is highly indicated. I suspect this was such a case.

Biodiesel may be cleaner than petrodiesel, but it's still diesel, and as such is not as clean as gasoline.

Good lord, how is gasoline clean?!?

how is gasoline clean?!?

Give me gasoline fumes over diesel fumes any day. Have you tried living in Europe? Not a nice experience to walk down a narrow street crowded with diesel cars...

Have you tried walking outside in Houston, LA, Atlanta on a summer day? Emissions from burning anything is not going to be good, gasoline included. Gasoline emissions are currently treated more comprehensively than diesel emissions (from an engine-out perspective gasoline is dirtier by every measure except PM by mass), but only for regulated pollutants. Regs say nothing about aromatics, aldehydes, PM by number, secondary particulate formation, etc. And regs still say nothing about CO2.

Anyway ... Upon what basis do they claim that PCAs (normally called Polynuclear Aromatic Hydrocarbons or PAHs) are unlikely to form during biodiesel combustion? It is my impression that PAH formation can occur in the combustion of nearly any carbonaceous fuel. The formation is disfavored by a very lean mixture.

A diesel typically runs at air-fuel ratios of 20-60:1, depending on load. By gasoline standards, that's extremely lean. In general, gasoline exhaust has higher PAH content than diesel exhaust. In terms of leakage emissions (such as at the filling station) biodiesel doesn't have aromatics to begin with; diesel ideally has low aromatic content (aromatics are great octane boosters but terrible for cetane); gasoline has high aromatic content. Gasoline also has a vapor pressure nearly 1000 times that of diesel, and bio even less.

Cidi, note that I said diesel was not as clean as gas. That means gas is cleaner, not that it is pristine. Levels of "engine out" pollutants are irrelevant. What matters is what comes out the (catalyst) tailpipe, and diesel presently loses that competition without question. Evaporative losses are not likely to be a significant source of PAHs, as their vapor pressure is not high relative to the major components of gasoline, given that they are C14 or so.

At some point in the future, probably around the time that I can buy a nice plug-in hybrid, I suspect that we will see "clean diesel" in America.

Levels of "engine out" pollutants are irrelevant. What matters is what comes out the (catalyst) tailpipe, and diesel presently loses that competition without question.

According to the EPA, definitely. But if you think the EPA is incomplete wrt toxic emissions, that statement is difficult to defend. The engine vs tailpipe out is only relevant in that you do have to work more to clean up gasoline, but it is true that today we do in fact do more to clean up gasoline emissions.

Evaporative losses are not likely to be a significant source of PAHs, as their vapor pressure is not high relative to the major components of gasoline, given that they are C14 or so.

Except that lighter components react in ambient air to form a huge number of heavier compounds with much lower vapor pressures (ie, form PM)

At some point in the future, probably around the time that I can buy a nice plug-in hybrid, I suspect that we will see "clean diesel" in America.

I'm hoping for primarily BEV, with a small biodiesel genset for longer runs.

It has been claimed that these calls for more research into alternatives to fossil fuels are in response to lobbying by the fossil fuel companies. When you look at who profits from raising doubts about biofuels then its hard to argue otherwise. Citing all the additives that MAY be in biodiesel gives the impression that many of the same additive are not in petrodiesel.

... University of North Carolina School of Public Health and the US EPA’s National Health and Environmental Effects Research Laboratory call for more research into the possible health effects of biodiesel exhaust ... Who is pushing this from UNC and EPA? Is it Exxon and Mobil funding and contributing to the debate? You always need to look into who is pushing for the "research" ... Follow the money ...

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