How much ethanol is too much

[Cap'n Jack]

We burn twice as much methanol racing versus gasoline. The reason we use methanol is because it has an octane rating of approximately 120 and it has a cooling effect that gasoline doesn’t.
I haven’t tried drinking it but I have plenty on my skin over the years with no side effects…yet!

Don't try drinking it. It's another way to go blind as methanol preferentially damages the optic nerve.

 

[Dan Thomas]

Please see my citations in post #64 for Aircraft Spruce and Parker/Stratoflex.
Aircraft Spruce lists fuel hoses for various Cessna and Beechcraft aircraft made under the Stratoflex brand. The Stratoflex link indicates the fuel lines are PTFE which are ethanol compatible.

Stratoflex had to get certification for that.

 

[Cap'n Jack]

Stratoflex had to get certification for that.

Yes, exactly!

The only place I found the newer stuff was in the fuel injection system, which is much newer and built by Precision Airmotove, not Cessna. Most of the hoses are still the old MIL-spec. Who is going to pay the freight to replace and recertify new compounds for a few hundred airplanes a year?

Apparently, Parker/Stratoflex will.

Please see my citations in post #64 for Aircraft Spruce and Parker/Stratoflex.

 

[Tools]

If I read and understand all this do I get a honorary degree in chemical engineering? Askin for a friend…. Wow. Wow…

 

[Pinecone]

I also could be wrong, but if so, why do some racers bother with running ethanol rather than gasoline?

1) Higher octane

2) the class rules require it (Indy Cars).

 

[pfarber]

As usual, a whole pile of bunk.

Lycoming's SI 1070 gives the specs for fuels their engines are certified to use:
https://www.lycoming.com/sites/default/files/attachments/SI1070AB%20Specified%20Fuels.pdf
Ethanol is NOT LISTED at all.

If we go to the Type Certificate Data Sheets for those engines, which the FAA issues to Lycoming when they certify an engine, we see this:

View attachment 132875

The dashed lines refer you back to the first entry; they're just ditto marks. That SI 1070 applies to ALL the O-235 models.
https://drs.faa.gov/browse/excelExternalWindow/0F97DB024367B9368625853C0061E215.0001
Ethanol is NOT listed anywhere.

The O-540's TCDS says this, for ALL O-540s (long list; this is just a short selection):

View attachment 132876

For the IO-540s:

View attachment 132878

And that applies to ALL IO-540 models. No ethanol. At all.
https://drs.faa.gov/browse/excelExternalWindow/ED61CF457FEE2DC686258250006AC097.0001

You didn't read the study, did you? Baylor said the FAA certified the IO-540 and o-235.

So who's wrong? Baylor? Peer reviewed studies? Or some guy with google and not reading past the first search page result?
Please READ the information and stop randomly googling.

Here we go.. AGAIN: https://afdc.energy.gov/files/pdfs/2896.pdf

Even with cited sources, peer reviewed studies, and links to .GOV and .EDU source materials some rando still thinks I'm making this up because THEY have weak google-fu.

Everything I am posting is coming from the Baylor study from the 90's. You can read it.. every word. PLEASE DO.

 

[Mikey52]

I wonder what carb modifications were done. After the valve recession was noticed.


And what is the Stc number? Can't seem to find it.

 

[Dan Thomas]

You didn't read the study, did you? Baylor said the FAA certified the IO-540 and o-235.

So who's wrong? Baylor? Peer reviewed studies? Or some guy with google and not reading past the first search page result?
Please READ the information and stop randomly googling.

Here we go.. AGAIN: https://afdc.energy.gov/files/pdfs/2896.pdf

So, let's see who certified what:


The certification was by Baylor, NOT BY THE FAA. Critical difference there. Show me in that document where the FAA certified the O-235s and O-540s to run on ethanol. https://afdc.energy.gov/files/pdfs/2896.pdf

Everything I am posting is coming from the Baylor study from the 90's.

Sure. The Baylor studies from the '90s. If the FAA had certified the O-235 and O-540 for ethanol, the TCDS would show it by now. The TCDS is the authoritative document published by the FAA for such things. Let's have a look at the O-235's TCDS:


Hm. See when it was last revised? January 31, 2020. That's at least 27 years after the Baylor studies. If the engine was indeed certified for use on ethanol, the TCDS would have shown that a long time ago.



The O-540 TCDS:



April 20, 2013, 20 years after the Baylor studies, and there is no certification shown for use on ethanol.

If you use fuels other than the engine was certified for, or STC'd for, you are in big trouble when it quits or when some FAA inspector discovers it. Mogas STCs specifically prohibit the use of gasolines containing ethanol:



And yes, ethanol qualifies as an alcohol.

 

[MacFlier]

Interesting discussion, thanks all.

I'm not yet on the island so I still have the opportunity to avoid cannibalism.

It's a choice of "southern route" through the island, with good weather, or "northern route" where weather is likely to be much less friendly. Unless I can confirm ethanol free mogas on the island somehow, it looks like the north route is a more sensible option.

Does anyone here speak Portuguese?

I do

 

[Domenick]

Because it is in their rules. Methanol is preferred, but methanol has more risks involved with it than ethanol. Methanol is flammable, toxic, and poisonous if ingested, inhaled, or in contact with the skin. Ethanol is toxic, flammable, and is safe for consumption as a critical ingredient of alcoholic beverages. It can be a dangerous chemical if pure alcohol is ingested.

Racing wise, the more alky you can stuff into a cylinder the more power is made, unlike gasoline.

Is the ethanol used in racing denatured or pure?

The potential lethal dose of methanol is 15 ml. That is 1 tablespoon.
The median lethal dose is 100 ml. That is less than 1/2 a cup.

The standard liquor shot is 44 ml, but consumable alcohol is 80 proof (40%) pure ethanol. 5 shots of pure methanol is 110 ml.

Methanol toxicity - Wikipedia

en.wikipedia.org

 

[Pinecone]

So, let's see who certified what:
View attachment 132899

The certification was by Baylor, NOT BY THE FAA. Critical difference there. Show me in that document where the FAA certified the O-235s and O-540s to run on ethanol. https://afdc.energy.gov/files/pdfs/2896.pdf

Sure. The Baylor studies from the '90s. If the FAA had certified the O-235 and O-540 for ethanol, the TCDS would show it by now. The TCDS is the authoritative document published by the FAA for such things. Let's have a look at the O-235's TCDS:

View attachment 132900
Hm. See when it was last revised? January 31, 2020. That's at least 27 years after the Baylor studies. If the engine was indeed certified for use on ethanol, the TCDS would have shown that a long time ago.



The O-540 TCDS:

View attachment 132901

April 20, 2013, 20 years after the Baylor studies, and there is no certification shown for use on ethanol.

If you use fuels other than the engine was certified for, or STC'd for, you are in big trouble when it quits or when some FAA inspector discovers it. Mogas STCs specifically prohibit the use of gasolines containing ethanol:

View attachment 132903

And yes, ethanol qualifies as an alcohol.

Do you understand how certification works?????

FAA does not certify things, They set the parameters for testing, may observe some tests, and then they issue the STC.

The STC modifies the TCDS. The airframe or engine manufacturer did not do the testing and certification, so there is no basic to change the TDCS. And the STC work is proprietary to the company owning the STC.

 

[Cap'n Jack]

Is the ethanol used in racing denatured or pure?

The potential lethal dose of methanol is 15 ml. That is 1 tablespoon.
The median lethal dose is 100 ml. That is less than 1/2 a cup.

The standard liquor shot is 44 ml, but consumable alcohol is 80 proof (40%) pure ethanol. 5 shots of pure methanol is 110 ml.

Methanol toxicity - Wikipedia

en.wikipedia.org

It is denatured ethanol to avoid taxes on it. They can put 2-propanol, gasoline (hydrocarbons and aromatic compounds), or other things in it. The E98 might not be 98% ethanol!

https://www.dlra.org.au/safety-data-sheets/powerpluse98-msds.pdf

https://www.sunocoracefuels.com/content/userfiles/files/fuel-selector/SUNOCO-Denatured-Ethanol-E98_US-SDS_22July20192.pdf

 

[Doc Holliday]

Do you understand how certification works?????

FAA does not certify things, They set the parameters for testing, may observe some tests, and then they issue the STC.

The STC modifies the TCDS. The airframe or engine manufacturer did not do the testing and certification, so there is no basic to change the TDCS. And the STC work is proprietary to the company owning the STC.

So what is the STC number to run ethanol in these engines? I would like to read up on it.

Thanks.

 

[Bob Noel]

Do you understand how certification works?????

FAA does not certify things, They set the parameters for testing, may observe some tests, and then they issue the STC.

The STC modifies the TCDS. The airframe or engine manufacturer did not do the testing and certification, so there is no basic to change the TDCS. And the STC work is proprietary to the company owning the STC.

apparently I don't understand the process today.

I thought an applicant proposes to the FAA how they (the applicant) intend to meet certification requirements. The FAA can reject or accept the plan. The FAA doesn't have to tell the applicant if the applicant is exceeding the requirements nor does the FAA have to explain specifically how to correct deficiencies ("bring me a rock" is not a bad simplification of the process).

When did the process change?

 

[Dan Thomas]

The Baylor University paper says this:



So we go to the FAA's STC site, https://drs.faa.gov/browse/STC/doctypeDetails

where all STC holders are listed alphabetically, and see if Baylor is listed as an STC holder:



Nope. Not there. So we check the names of the authors of that study, as listed on the header of the paper:


And we see this:



And Mr Tubbs is not listed:



Nor is Zanin:



So we check out the two STCs issued to Dr. Shauck:

https://drs.faa.gov/browse/excelExternalWindow/EBFE06A026CE1AAF8625702800648327.0001

And sure enough, there's an airframe certified to run on ethanol, but only the Piper PA-25 (Pawnee, a single-place cropsprayer):



And the other STC granted to Dr. Shauck:
https://drs.faa.gov/browse/excelExternalWindow/8ACA8B27ED9A07A98625702800641E1C.0001



It covers a few models of the O-540, and a few of the IO-540 as well. So we have the first STC that was the airframe certification since no engines are listed, and the second covers the engines that might be found in the PA-25.

So it turns out that P. Farber is partly right, as far as this goes. There is no STC granted to Dr. Shauck, his colleagues, or Baylor University or its Renewable Aviation Fuel Development Center to run an O-235 or a Cessna 152 airframe on ethanol. None at all. It may have been applied for as per the paragraph from the paper at the head of this post, but never granted.

Edit: I made a few textual changes there, and did a little more digging. The STC database decided to show me this STC for the O-235 to run on ethanol: https://drs.faa.gov/browse/excelExternalWindow/975B5C200682D2708625740300821009.0001

It came up when searching under Dr. Shauck's name but the STC is issued to some Texas outfit. Shauck must have been involved with it.



Still no STC for the 152 airframe, and you need STCs for both the engine and airframe to be legal. But maybe if I check "Shauck" again in a few days, the database might find one.

Edit again: I checked Maximum Performance Inc. for the 152 airframe ethanol STC. None are listed.

 

[chemgeek]

A potential problem with ethanol is that is has about double the vapor pressure of avgas. Higher ethanol content will create a higher potential for fuel line vaporization and vapor lock. Ethanol is also hygroscopic, so water absorption by fuel is also a potential issue. The extent of the potential problems scale with ethanol content.

 

[455 Bravo Uniform]

So who's wrong? Baylor? Peer reviewed studies?

I read the study you posted.

In academia, some papers end up at the end of a cul de sac, while others end up on a main road. Sometimes it’s because the study results couldn’t be verified or repeated, or not enough interest or funding (insert conspiracy theories, but funding begets studies that get funded, while others that may be unpopular or go against the grain can get hung out to dry).

I haven’t done it yet (I will, later tonight) but you can go to a publication database and see how many other authors in the field cited this report, and all of the prior and later works from these authors. That usually tells you about the significance of the results.

 

[455 Bravo Uniform]

Ethanol is also hygroscopic, so water absorption by fuel is also a potential issue. The extent of the potential problems scale with ethanol content.

Since ethanol & water are miscible, up to some point water in the fuel should be no problem. At what point does it become a problem where it affects power or ability to combust?

 

[Capt. Geoffrey Thorpe]

At what point does it become a problem where it affects power or ability to combust?

At the point which the water and ethanol separate from the gasoline.

"at 60 degrees F, water can be absorbed by a blend of 90%
gasoline and 10% ethanol up to a content of 0.5 volume percent
before it will phase separate. This means that approximately 3.8
teaspoons of water can be dissolved per gallon of the fuel before
the water will begin to phase separate."

https://www.epa.gov/sites/default/files/2015-09/documents/waterphs.pdf

 

[455 Bravo Uniform]

At the point which the water and ethanol separate from the gasoline.

"at 60 degrees F, water can be absorbed by a blend of 90%
gasoline and 10% ethanol up to a content of 0.5 volume percent
before it will phase separate. This means that approximately 3.8
teaspoons of water can be dissolved per gallon of the fuel before
the water will begin to phase separate."

https://www.epa.gov/sites/default/files/2015-09/documents/waterphs.pdf

Thanks. I was referring to the 100% ethanol potion of this discussion with my question.

 

[Albany Tom]

Thanks. I was referring to the 100% ethanol potion of this discussion with my question.

Not a chemist, but I don't think they ever separate at room temp/pressure. AFAIK, water and ethanol are miscible in any ratio. If they weren't, mixed drinks wouldn't work at all ratios.

Now as others have pointed out, gasoline with a bit of ethanol is miscible and with a bit of water, too. Once the water gets high enough, the water and ethanol drop out. And as we all know, with pure gasoline and water the water drops out.

 

[455 Bravo Uniform]

Correct. My question is about power and combustion. As to burning, we can light stuff at 101 proof (50.5% ethanol). Where it stops working in an ICE or making enough power to takeoff is probably higher. So incidental/inadvertent water in supposedly 100% ethanol fuel becomes less of an issue than in gasoline.

 

[Dana]

So: Most engines will run just fine on varying amounts of ethanol. At higher concentrations, jetting adjustments may be required. The energy content of ethanol is somewhat lower, so maximum power is slightly reduced and fuel consumption at the same power setting is higher.

The big problem is with the ancillary parts... like the carburetor float needles that Ron W mentioned; some, including original Stromberg parts, were fine, others (still PMA'd) from other suppliers were not... and often no way to tell them apart.

Vapor pressure can be an issue, which is why most high wing aircraft with gravity feed fuel systems could get a mogas STC while most low wings with electric fuel pumps could not.

Water dissolved into ethanol in any likely amount poses no problem, except that it isn't detectable... until the fuel cools and it separates, like when the tanks cool as you climb into cooler air.

Ethanol in a glass (preferably neat, from Scotland) can cause other problems, of course.

 

[chemgeek]

Since ethanol & water are miscible, up to some point water in the fuel should be no problem. At what point does it become a problem where it affects power or ability to combust?

It becomes a problem when the water/ethanol concentration exceeds that which can be sustained by the largely hydrocarbon fuel mixture. Then the water phase will start separating out.

 

[455 Bravo Uniform]

It becomes a problem when the water/ethanol concentration exceeds that which can be sustained by the largely hydrocarbon fuel mixture. Then the water phase will start separating out.

Was talking about 100% ethanol as fuel.

 

[Dan Thomas]

So: Most engines will run just fine on varying amounts of ethanol. At higher concentrations, jetting adjustments may be required. The energy content of ethanol is somewhat lower, so maximum power is slightly reduced and fuel consumption at the same power setting is higher.

That shot from the Pawnee ethanol STC again:

So straight ethanol is OK. Straight 100LL is OK. But mixtures of ethanol and Avgas are limited to a max of 25% Avgas. Why would that be? Obviously, there must be a reason. Do our resident chemists have any idea?

If we go to the other STC, the one for the O-540 engine, we see the same thing:

The big problem is with the ancillary parts... like the carburetor float needles that Ron W mentioned; some, including original Stromberg parts, were fine, others (still PMA'd) from other suppliers were not... and often no way to tell them apart.

If we bought the STC from the owner, we would get Instructions for incorporating it. Those instructions are not posted in the STC database. I am certain that changes to hoses and seals would be required. Ethanol is just too destructive to the older polymers.

NBR (Acrylonitrile-butadiene rubber) is used, in similar compoundings, in the MS28775 and MS29513 O-rings. 28775 is commonly used for hydraulic fluids, 29513 for gasolines. If we go to a handy chart like this one, we can see what effects gasoline and ethanol have on NBR: https://www.allorings.com/o-ring-compatibility

Let's see if I can chop the chart up and show the relevant sections:





We see that NBR has poor chemical resistance to ethanol, good resistance to gasoline, and for gasohol (the mix of gasoline and ethanol) it is not recommended at all.

There are a half-dozen compounds shown there that would work for straight ethanol. They would have to be narrowed down to those with good temperature stability, resistance to other chemicals they might encounter (gasoline, of course, and maybe Varsol) and so on.

 

[Cap'n Jack]

That shot from the Pawnee ethanol STC again:
View attachment 133015
So straight ethanol is OK. Straight 100LL is OK. But mixtures of ethanol and Avgas are limited to a max of 25% Avgas. Why would that be? Obviously, there must be a reason. Do our resident chemists have any idea?

If we go to the other STC, the one for the O-540 engine, we see the same thing:
View attachment 133016

If we bought the STC from the owner, we would get Instructions for incorporating it. Those instructions are not posted in the STC database. I am certain that changes to hoses and seals would be required. Ethanol is just too destructive to the older polymers.

NBR (Acrylonitrile-butadiene rubber) is used, in similar compoundings, in the MS28775 and MS29513 O-rings. 28775 is commonly used for hydraulic fluids, 29513 for gasolines. If we go to a handy chart like this one, we can see what effects gasoline and ethanol have on NBR: https://www.allorings.com/o-ring-compatibility

Let's see if I can chop the chart up and show the relevant sections:

View attachment 133017
View attachment 133018
View attachment 133019

We see that NBR has poor chemical resistance to ethanol, good resistance to gasoline, and for gasohol (the mix of gasoline and ethanol) it is not recommended at all.

There are a half-dozen compounds shown there that would work for straight ethanol. They would have to be narrowed down to those with good temperature stability, resistance to other chemicals they might encounter (gasoline, of course, and maybe Varsol) and so on.

So, what's your point? It's already been established that most planes need changes to fuel hoses (already available from Aircraft Spruce), seals, etc. Automobiles run on methanol or ethanol at racetracks, so the seal materials exist, if needed.

 

[Dan Thomas]

So, what's your point? It's already been established that most planes need changes to fuel hoses

My point? To counter nonsense like this:

Hate to burst everyone's bubble (not really, you'all just wrong sometimes).

What if I told you the FAA ran a Cessna 152 and an IO-540 on 100% ethanol and did nothing to airplane except a minor mixture adjustment?
......
The only thing stopping 100% ethanol is the petroleum industry and old wives tales. Rubber is not the problem. In 13 YEARS the 100% ethanol 152 never had a fuel related issue.

Several dangerous assumptions there.

Automobiles run on methanol or ethanol at racetracks, so the seal materials exist, if needed.

Yes, they do exist. I posted it in that chart. Nowhere did I suggest that it was impossible or difficult to find the right stuff. It was obviously available when those STCs were issued 20+ years ago.

 

[Cap'n Jack]

Yes, they do exist. I posted it in that chart. Nowhere did I suggest that it was impossible or difficult to find the right stuff. It was obviously available when those STCs were issued 20+ years ago.

See your post #74

 

[Dan Thomas]

See your post #74

And from that post:

Most of the hoses are still the old MIL-spec. Who is going to pay the freight to replace and recertify new compounds for a few hundred airplanes a year? And Cessna won't spend bucks on the legacy stuff. Someone might come up with STCs, but those aren't cheap, so most would just keep using the old stuff.

The ethanol STCs will have the hose and seal replacement instructions, as I said in post #106:

If we bought the STC from the owner, we would get Instructions for incorporating it. Those instructions are not posted in the STC database. I am certain that changes to hoses and seals would be required. Ethanol is just too destructive to the older polymers.

 

[AV8R_87]

The executive summary, going back to the OP, seems pretty straightforward.

Unless that plane has a completely rebuilt fuel system, from tanks to carb/fuel injection system, with every component in it accounted for and known to be compatible with ethanol, and with airframe/engine approvals (STCs, field approvals, you name it) for use of ethanol fuel, the answer is "anything over 0% ethanol is too much".
Regulatory answer aside, not knowing the exact formulation for the fuel system rubber components (every single one of them), you'd still be playing Russian roulette. And I doubt the average owner (or even the above average one) can tell you what particular elastomer formulation is used in the carb or fuel selector valve seals, for example.

In conclusion, not a decision I'd make last minute just because avgas is not available.
If the situation is dire, I'd figure out a standalone way to atomize fuel in the intake manifold that completely bypasses the existing fuel system. Get a few fuel storage containers, a fuel pump, some lines and an injector from a car and have that spray fuel into the intake manifold at a controlled rate.

 

[Cap'n Jack]

The ethanol STCs will have the hose and seal replacement instructions, as I said in post #106:

And I didn't see the need for any STC's for the Cessna and Beechcraft PTFE, ethanol compatible, hoses I cited. Rotax engines run fine with up to 10% ethanol.

 

[Dan Thomas]

And I didn't see the need for any STC's for the Cessna and Beechcraft PTFE, ethanol compatible, hoses I cited. Rotax engines run fine with up to 10% ethanol.

The hoses are built to a TSO spec acceptable to the FAA. From the Stratoflex catalog:



So the installer still has the responsibility to see that the hose will perform safely as installed, and to use installation guidance such as found in AC43.13.

A straight-ethanol STC would specify ethanol-resistant hoses that would not likely have their own STCs, but acceptable TSOs.

Rotax would have started out using technology much newer than Cessna or Beech or Piper or Mooney did.

 

[MackMooney]

shrug, when my tanks need resealing, i'd pay extra dollars to have the the lines, fuel pump and spider made compatible, heck i'd be overhauling them anyway

 

[Ghery]

Hate to burst everyone's bubble (not really, you'all just wrong sometimes).

What if I told you the FAA ran a Cessna 152 and an IO-540 on 100% ethanol and did nothing to airplane except a minor mixture adjustment?

The engine made MORE HP, and they could not get it to detonate.

The only thing stopping 100% ethanol is the petroleum industry and old wives tales. Rubber is not the problem. In 13 YEARS the 100% ethanol 152 never had a fuel related issue.

Must have had better seals than my 1986 Dodge van. The parting words from the salesman as we drove it off the lot were, "Don't put ethanol in it!" Shortly later California mandated "oxygenated" gasoline. That was their way of saying, "polluted with ethanol". A little while later I had raw gas pouring over the engine as the ethanol ate the seals out on the fuel system. Did California pay for the damage they created? Who are you kidding!

I will NOT put ethanol in anything that is not designed for it. Period. End of discussion.

 

[Domenick]

Would someone please just soak a few new/old seals and appropriate hose pieces in a cup of drugstore 70% rubbing alcohol (ethanol)?
Potential seals for the experiment:
Gas tank sender gasket
Fuel bladder material
primer o-rings
fuel drain o-rings
fuel line (hose)
carb gaskets and seals
??

 

[Dana]

Would someone please just soak a few new/old seals and appropriate hose pieces in a cup of drugstore 70% rubbing alcohol (ethanol)?
Potential seals for the experiment:
Gas tank sender gasket
Fuel bladder material
primer o-rings
fuel drain o-rings
fuel line (hose)
carb gaskets and seals
??

Rubbing alcohol is isopropanol (propyl alcohol), not ethanol.

And there are many different rubber formulations, even for the same item different vendors may use a different formulation. One may be OK while another supposedly identical one may not.

 

[455 Bravo Uniform]

Would someone please just soak a few new/old seals and appropriate hose pieces in a cup of drugstore 70% rubbing alcohol (ethanol)?
Potential seals for the experiment:
Gas tank sender gasket
Fuel bladder material
primer o-rings
fuel drain o-rings
fuel line (hose)
carb gaskets and seals
??

You want booze. Most liquor is around 40-50% ethanol. Some rum is 75%. You can also buy a 95% spirit in some places (Everclear is the only brand I know). You can also distill it yourself legally if for fuel use…

 

[Capt. Geoffrey Thorpe]

Some materials may be resistant to both gasoline and ethanol, but not a combination of the two. For example, I just happened to be looking at the specs for some PETG sheet the other day - listed as resistant to both ethyl alcohol and gasoline, but not gasohol...

https://plaskolite.com/docs/default-source/fab/fab001_viv.pdf page 14


Running on 100% gasoline or 100% ethanol is not the same as running on a mix.

 

[Cap'n Jack]

You want booze. Most liquor is around 40-50% ethanol. Some rum is 75%. You can also buy a 95% spirit in some places (Everclear is the only brand I know). You can also distill it yourself legally if for fuel use…

If you distill it yourself, it will still be 95% as that is an azeotropic mixture. Adding benzene makes a different mixture than can be distilled again to make 100% ethanol with traces of benzene.