When Synthetic Fuels go bad: MTBE

[hunter]

Back in the bad old days, when I was a kid, various lead compounds were used to "boost" the octane of raw gasoline for use in automobile engines. This lead polluted the air and was found to be damaging the nervous systems of young children, especially in urban areas. The use of lead in gasoline was eventually banned.

During the phase-out of "leaded" gasolines some oil companies began using small amounts of Methyl Tertiary Butyl Ether (MTBE) as an octane booster in their gasoline blends.

The 'seventies and 'eighties were a time of rapid advances in the petro-chemical industry. Several efficient ways of making MTBE from low value refinery products and natural gas streams were developed. This MTBE could then be added to higher value gasolines at volumes up to 15%.

It seemed to be a win-win situation. Making MTBE was profitable, it increased the overall gasoline supply, and it reduced some kinds of air pollution. There were small problems with the fuel systems of some cars -- cars that happened to have fuel seals that were not resistant to MTBE -- but that was a problem that could be fixed.

MTBE became a very common additive in gasoline, and laws were passed that encouraged the use of MTBE.

Then MTBE showed its ugly side. The undergraound storage tanks of the gasoline business turned out to be far leakier than anyone suspected, and MTBE started showing up in our water.

Old style gasolines did not dissolve in water to any great extent, and whenever gasoline leaked, natural processes tended to keep it segregated. And surprisingly, certain species of soil bacteria were discovered to be consuming many components of spilled fuels.

This was not the case with MTBE. MTBE dissolves quickly in water, and it is very difficult to remove. That is why there has been such outcries against MTBE. We don't want it in our drinking water.

A few days ago the Bush administration very clearly stated they did not support the banning of MTBE. Some people here at DU have framed this as a Chemical Industry vs. Ethanol Producers argument, or as a Bush vs. The Environment argument, but I don't buy that.

I believe the Bush administration is afraid there will be gasoline shortages this summer. If there are serious shortages voters will blame Bush and he will be thrown out of office. Therefore the Bush administration hopes to use MTBE, a sort of synthetic gasoline, to increase the gasoline supply. And it certainly doesn't hurt Bush that he has friends in the MTBE business.

Nevertheless, I think there is a broader lesson here, whenever we talk about "alternative" or synthetic fuels, be they biodiesel, DME, ethanol, or so on... All of these fuels are going to come with some unique set of problems, and none of them are going to be any sort of "magic bullet" that will eliminate our dependence on foreign oil and let us drive our trucks and cars wherever and whenever we please, forevever and ever.

[treepig]

1. maybe, maybe not . . .

you say Old style gasolines did not dissolve in water to any great extent, and whenever gasoline leaked, natural processes tended to keep it segregated. And surprisingly, certain species of soil bacteria were discovered to be consuming many components of spilled fuels.

This was not the case with MTBE.

others say:

Characterization of MTBE-Degrading Bacterial Isolates and Associated Consortia
Jessica Hanson, Graduate student
Kate Scow, Ph.D., PI
[e-mail]
Mary Ann Bruns, Ph.D., Postdoctoral Researcher
Todd Brethour, Undergraduate student
Land Air & Water Resources
University of California, Davis

Contrary to some previous reports, methyl tertiary-butyl ether (MTBE) can be biodegraded. We have isolated two bacterial strains, PM1 and YM1, which are can use MTBE as their only source of carbon and energy. These strains were obtained from a mixed microbial consortium provided by the University of California, Davis Department of Civil and Environmental Engineering. MTBE degradation by PM1 is rapid (complete disappearance of the pollutant within 4 days), and is not affected by the addition of small amounts of nutrients. YM1 degrades MTBE more slowly (50% degraded in 4 days) and nutrients appear to enhance MTBE degradation. Examination of whole cell lipid profiles for PM1 and YM1 indicates that they are not identical strains. Thermal gradient gel electrophoresis (TGGE) analysis of 16S rRNA gene fragments from the two strains, however, showed no difference between them. 16S rDNA sequence analysis of strains PM1 and YM1 revealed that they are both most closely related to the genus Sphingomonas.

Biodegradation of Methyl-t-Butyl Ether by Pure Bacterial CulturesK.Mo, C. Lora, A. Wanken and C.F. Kulpa. University of Notre Dame, Notre Dame, IN 46556

Methyl-t-butyl ether (MTBE) a gasoline oxygenate to reduce carbon monoxide emissions has become widely used in the petroleum industry. It is already one of the fastest growing chemical products of the last few years. There is little data on the biological fate of MTBE. No information about biodegradation of MTBE by pure cultures has been reported. We have isolated fifteen pure bacterial strains from biotreater sludges and other sources with the capacity to degrade on MTBE when it is the sole carbon source. Seven strains have been classified as belonging to the genus's Rhodococcus, Flavobacterium, Pseudomonas, or Oerskovia. These cultures degraded up to 40% of 200 ppm of MTBE in 1-2 weeks of incubation at 22-25C. These strains also grow on t-butanol, butylformate, isopropanol, acetone and pyruvate as sole carbon sources. Use of these compounds in combination with MTBE showed a reduction in the degradation of MTBE. However, pregrowth on t-butanol followed by transfer to medium containing MTBE resulted in greater degradation of MTBE. Uniformly-labeled 14C-MTBE was used to determine 14C O 2 evolution. Within 7 days of incubation, significant radioactivity was evolved as 14C O 2. The growth of some isolates on MTBE is very slow, however, in some instances, very little increase in cell number occurs even though degradation of MTBE is occurring. The availability of pure cultures that degrade MTBE will allow the determination of the pathway intermediates and the rate limiting steps as well as considerations for bioaugmentation. (Presented at American Society for Microbiology meeting, 1995, Washington, DC)

you say I believe the Bush administration is afraid there will be gasoline shortages this summer. If there are serious shortages voters will blame Bush and he will be thrown out of office. Therefore the Bush administration hopes to use MTBE, a sort of synthetic gasoline, to increase the gasoline supply.

i suggest analyzing this (or similar) websites:

http://www.eia.doe.gov/emeu/steo/pub/special/mtbecost.html

the gist seems to be the mtbe is more expensive than gasoline (so increased usage will do nothing but increase the already high cost of gasoline, probably not something mr. bush wants to happen in an election year). further, one of the (major?) feedstocks for mtbe is natural gas - and if anything, isn't natural gas is in shorter supply than good old fashioned crude oil?

[hunter]

2. Nice research...

If something can be used as food, eventually you will find a bacteria that eats it. I have no doubt that wild bacteria are already feasting on MTBE. That doesn't solve the environmental problem.

The problem is that MTBE diffuses more rapidly through water than other gasoline components, and it is very difficult to remove from domestic water supplies.

I have no doubt that MTBE eating bacteria will be very useful in biological water treatment systems, but it's difficult to apply such solutions to entire watersheds and groundwater resources.

My response to your second point is to say that the economics of MTBE are more complicated than any simple price per gallon.

A long time ago gasoline was made by distilling crude oil. You kept all the stuff that condensed out at a certain temperature, added some "ethyl" lead to it, and sold that as motor fuel.

Nowadays gasoline is an entirely synthetic product. Crude oil is sent through all sorts of chemical contortions to maximize the production of high value products, and minimize the production of low value products.

As an octane booster, MTBE increases the value of lower octane gasoline that couldn't otherwise be used as a motor fuel. This low octane gasoline is, in fact, made with the expectation that some sort of octane booster such as MTBE will be added to it.

Without MTBE or some other octane booster the overall yield of gasoline from a barrel of crude oil is decreased. So, even though MTBE may be "more expensive than gasoline" it is still profitable to add it to the motor fuel supply.

[treepig]

3. my understanding is that mtbe shortages drive up gasoline prices

correct me if i'm wrong, but government mandates the use of oxygenated fuels in certain areas at certain times of the year to reduce smog. therefore, there is an "artificial" demand for mtbe - and i wouldn't doubt at all the mtbe "shortages" during these times are equally artificial, all intended to drive up the price, thereby making mtbe very profitable. in any event, the link i provide above demonstrates the "profitability" of mtbe if judged by no other standard than the fact that it demands a higher price than the equivalent volume of gasoline.

what is less clear to me is if mtbe would be profitable - when profitable is defined as a benefit to the consumer, not the mtbe manufacturer - in an entirely free market scenario. more specifically, is your point that in the absence of any government mandates or bans, mbte would be added to fuels and benefit both the producer and consumer? (i.e., the producer would benefit because in the free market, mtbe is actually less costly than the gasoline it replaces, and the consumer would all benefit because part or all of the cost saving realized by the manufacturere would, or at least could, be passed on?)

in any event, if mtbe isn't added, then what will be added as an octane booster? ethanol is a rather poor substitute, considering it's lower energy content (26.7 MJ/kg compared to 35.2 for mtbe and ~43 for "gasoline"). xylenes and benzene are other options, by they're rather toxic (unlike mtbe which is foul, but not really toxic).


i still haven't figured out why no one cares to address the root problem here - the freaking leaking gasoline tanks. after all, natural gas has foul-smelling odorants added specifically so that leaks will be detected, and patched. why can't mtbe considered to provide the equivalent function for gasoline?

[hunter]

4. I thought some more about this, and now I feel cynical...

At some point the oil companies must have decided that adding MTBE to the production process would increase their profits. It makes sense because adding MTBE to the loop allows each barrel of oil to yield higher value products.

Also, with an eye towards the future, MTBE doesn't have to be made from natural gas or petroleum. Any source of methyl alcohol and four carbon molecules might be used. (Coal and oil sands would be the most obvious carbon sources.)

People who complain about MTBE are correct when they smell something fraudulent about the business. We are not really using MTBE to reduce smog -- that was simply a very clever sales gimmick. It worked so well that any criticisms of the oil business for adding MTBE to their products have been deflected onto the government and those whacky environmentalists.

[ChemEng]

5. Wrong

I work in this business and I can tell you that there have been enough studies done proving the benefcial effect of MTBE on air quality.

If MTBE were so bad, why aren'y the Europeans banning it? Because their damn gas tanks don't leak!! Why? Because they tax gasoline at the terminal, not at the pump.

The real shame is that MTBE allowed refiners to stretch the gasoline pool,and now we will pay higher prices for gasoline. All so that ADM can have higher profits from ethanol. And I'm sick and tired of paying ADM for it....

[hunter]

8. I never said MTBE did not improve air quality...

But that's not why they put it in our gasoline.

I haven't run all the numbers and I'm not going to go off digging for proprietary information, but I suspect we'd have MTBE in our gasoline even if MTBE did not improve air quality.

ADM and ethanol? Yes, I agree, that is the sort of thing that can make one very "sick and tired" (...in a Bob Dole, Paul Harvey, Viagra, and Britney Spears sort of way.)

[NNadir]

6. The MTBE case is an interesting risk/benefit case.

I am not sure what the half life of MTBE is in water, but it is probably not a persistant compound, especially in acidic water. I would expect it breaks down rather easily to give isobutylene and methanol. Still, it is persistant enough and water soluble enough (although it is in no way miscible with water) that, if it has some toxicity, it needs to be carefully monitored.

But the entire question is one that bears careful examination. It is clear that oxygenation has a beneficial effect on combustion, and thus minimizes and this is why people like to promote oxygenated fuels. Biodiesel advocates here and elsewhere like to refer as biodiesel as a oxygenated fuel, even though it consists largely of compounds that are esters of things like lineolic acid, a far more alkene (or alkane) like compound than it is "oxygenated." Compounds like MTBE are much more highly oxygenated, on the basis of carbon to oxygen ratios.

The question is this: Does the oxygenated fuel actually reduce risk of air pollution to compensate for the risk from contaminated water? To answer this question we need to know about the prevalence of MTBE leaks, and also about the toxicity associated with such leaks. MTBE certainly can decompose to give reactive species, such as carbocations, but on the other hand tert-butyl groups are found widely, particularly in some important drugs.

We should also remember that gasoline is just chock full of toxic compounds, including benzene, which has some water solubility. Underground gasoline tanks should be monitored and regulated. That this does not happen is a function of Republican anti-environmental regulation ideology.

The real problem with MTBE is that it is relatively high boiling. The fuel that I advocate, DME, is actually a liquifiable gas. However my biggest concern about my preferred alternative is indeed water solubility of this gas. In equilibrium with air, the DME will indeed get out of the water, but this isn't particularly satisfying. Although it is very clear to me that it is relatively easy to remove DME from water by aeration, I should also note that most people do not aerate their water. To err on the side of honesty, I also note that a drawback to DME is that it is most likely a greenhouse gas, albeit one that is not particularly persistant. Those who are familiar with my thinking though will recognize that I do not expect perfection in any alternative. I simply prefer to choose the option that is most likely to result in the least environmental disruption of a vastly overpopulated world.

Before the oxygenation of gasoline, I worked with MTBE as a solvent in the lab. I don't believe that I had profound health effects from it, but then again, I'm not sure that I'm representative of the entire population.

[NNadir]

7. Some MTBE facts.

Thinking about this interesting question, I came across this website from the European Fuel Oxygenates Society. It gives some insight to the issues associated with MTBE, but of course, should be regarded as biased.

Interesting is the part of the website that compares the issue of the differences between Europe and the United States. One such difference is that in Europe, fuel is highly taxed and therefore more expensive. This adds incentive to the sellers to control leaks, since leaks cost more money.

I have long been an advocate of higher fuel costs through taxation, especially to address environmental (generally uncharged) costs. Unfortunately this idea is probably less politically viable than it is in Europe.

One thing is for certain: Bush plundering and environmental hostility makes for difficulty in making sober environmental assumptions. One feels almost compelled to view any of their decisions as environmentally suspect, although it may happen, through a coincidence of interests (plunder for them, environmentally beneficial consequences for us) that some of what they propose is not necessarily environmentally destructive.

BTW, Hunter, I do agree with your implication that we need to drive less. When we do drive we need to do so with the most efficient systems possible. Hummers don't cut it.

MTBE, A European Perspective