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MTBE. As a fuel additive, is it more harmful than helpful?. Slides produced by: Robert Bennigsdorf. What is MTBE?. Technically speaking, it’s “ M ethyl T ert- B utyl E ther”. Visually it is:. Q: But what is it used for?. A: As a fuel additive. PURPOSE OF MTBE:.

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As a fuel additive, is it more harmful than helpful?

Slides produced by:

Robert Bennigsdorf


What is MTBE?

Technically speaking, it’s “Methyl Tert-Butyl Ether”

Visually it is:

Q: But what is it used for?

A: As a fuel additive.



When gasoline is burned, one possible byproduct is carbon monoxide

CO =

One way to eliminate the production of carbon monoxide is to add an oxidizing agent to turn the carbon monoxide into carbon dioxide.

CO + Oxidizer


But was MTBE always the oxidizing agent used?


Answer: NO!

Fuel used to have lead in it (thus the reason why we buy unleaded fuel now).

The lead used to act as the oxidizing agent until the 1970s when the adverse health effects from lead were fully realized and then new additives had to replace it.

Currently we use a combination of alcohols, ethers and the highly toxic and cancer-causing benzene.

The ether that we use is known as MTBE.



Simply put, the problem with MTBE is that it is way too soluble in water.

Approximately 50,000 mg per liter can be dissolved.

When gasoline enters the environment, the solubility of MTBE is far greater than that of gasoline or the other additives, this creates the current problem where MTBE quickly enters the ground water and travels it is wherever it goes – even to the water supply.

How does MTBE enter the environment?


MTBE (through gasoline) can enter the environment through 4 main ways:

1. Through leaking underground tanks

Many of the tanks that store gasoline at factories or gas stations are old and in need of repairs or replacement. In a study from 2000 from the USGAO showed that 29% of USTs were in need of repairs (accounting for 14,500 leaks). 1

2. Spills

Gasoline spills from filling accidents and car accidents

3. Watercrafts

Watercraft engines routinely release some unused fuel into the oceans.

4. Vaporization

Every time you fill up with gas, some escapes as vapors, with MTBE.

Moyer, Ellen. MTBE Remediation Handbook, Amherst: Amherst Scientific Publishers, 2003. pg 7.



Honestly….it stays there.

MTBE is extremely difficult (and therefore extremely expensive) to clean up. Reason: it is just too darn soluble in water!

California Data of MTBE contamination is:

0.8% of drinking water supply contained detectable levels of MTBE

95% contained no MTBE, of the remaining 5%:

73% were below the level the state recommended. 2

2. Moyer pg 68


Then why all the attention?

In 1997 the city of Santa Monica did reach the level of contamination had was forced to shut down half of it water wells.

This resulted in a 75% loss of the groundwater supply for the city and $3 million had to be spent bringing in bottled water.3

-WELL, what actually can MTBE do to you if its so bad?

Honestly…nothing that we can really say.

3. Jacobs, James. MTBE effects on soil and groundwater resources. London: Lewis Publishers, 2000. pg 11.



Not that we know of


Not that we know of

Can MTBE actually cause cancer in humans?

Not that we know of




According to a 1998 publication from the California State Senate:

“There are studies in rodents showing MTBE has potentially carcinogenic properties in high doses. Exposure was associated with a dose-related increase in leukemia and lymphomas in female rats and an increase in benign testicular tumors in male rats. There are two studies of the potential carcinogenicity of MTBE after inhalation exposure. One study showed exposure caused an increase in the incidence of kidney tumors, both malignant and benign, as well as testicular tumors in male rats. The other showed significant increases in malignant liver tumors in male mice and non-malignant liver tumors in female mice.”4

But how high is this “high dose” mentioned above?

It is 1,000mg per 1kg body mass for 104 days.5

Do we need to worry about this concentration being present right now?

Not really, since we can smell MTBE at 20 ppb and taste it at 40 ppb.

4. Does California need MTBE? California State Senate publication 98-4/A May 1998.

5. Jacobs pg 26.


Did these studies have any effects?

Yes they did.

Former Governor Gray Davis encouraged the phasing out of MTBE by December 31, 2001

Furthermore the US government has begun investigation the use of alternative fuel additives that can do the same thing.

What else can do it?

Well, I mentioned that there were three things that could be fuel additives:






Ethanol is a wonderful compound with many great properties…..

Such as also being an oxidizing agent

Ethanol can also oxidize carbon monoxide into carbon dioxide, though obviously not as well since we’d be using ethanol instead of MTBE this whole time, which really would make this presentation unnecessary since there is no danger of ethanol invading our water supply except for maybe more homeless people drinking out of water fountains and for the nonexistence bottle water companies…

So what is the big problem with using ethanol??



If we were to switch over to only ethanol and no MTBE, gasoline would cost a WHOLE BUNCH MORE.

You want proof? California already requires a high percentage of ethanol that other states (Davis….) and it is reflected in gas prices:

The latest data from showed national average for regular gas was $1.98 gallon, whereas California was second highest with $2.25 (only hawaii higher where they have like 1000 miles of ocean to get it to there).


So we can see that if we were to change completely to ethanol we would decrease the amount of MTBE in the groundwater, but we’d also decrease the amount of money in our wallets.

Is Congress then going to stop pushing ethanol?

Unlikely, see, ethanol can come from corn, which is grown in the good old US of A (think Iowa and Nebraska, not much there but corn, lots and lots of corn…)

In fact, I got from the library a 195 page transcript of a hearing from July 2, 2003 from the committee on government reform of the US House of Representatives titled: “California Gasoline Markets: from MTBE to ethanol”


Side note:

My least favorite part of the transcript was when the discussion of ethanol’s higher vapor pressure would cause a decrease in the volume of gasoline actually produced versus MTBE. This would cause an increase in cost per gallon of 3 to 6 cents per gallon just from that loss. This would equal $33 to $66 million per month from California drivers to ethanol producers in Iowa and Nebraska


So, it is a choice between the environment and money?

Yes and no.

To suggest that MTBE is horrible for the environment and that ethanol has no negative affects is wrong.

Ethanol can also negatively affect the environment by not working as well as MTBE and thus allowing more poisonous carbon monoxide into the atmosphere.

There is also one more downside to ethanol, and that is the problem of energy.


There exists a good argument against the move to ethanol, and this one of the energy required to refine ethanol.

I said earlier that ethanol can be refined from corn, though I never said how this is done. The answer, as in all things, energy.

The energy required to refine the ethanol from corn is actually greater than the energy that the ethanol will ultimately produce when burned, and this difference is much greater.

The problem lies in where this energy comes from…fossil fuels of course!!

This doesn’t really help the environment to burn fossil fuels in order to keep the groundwater clean, or so goes the argument.


So what are we to do? Clean Air or Clean Water?

This is the ultimate question, and one that is not easily answered, the only help that I will leave is a quote found in the front of one of the books on MTBE:

“The significant problems we face cannot be solved at the same level of thinking we were at when we created them.”

-Albert Einstein

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