NREL Team Tests Higher Ethanol Fuel Mix

NREL Team Tests Higher Ethanol Fuel Mix
Storage canisters lined up in NREL's lab hold gas emission from cars that got a taste of higher levels of ethanol in the gasoline. Study results so far have shown that as ethanol increased, tailpipe emissions stayed largely the same. Credit: Heather Lammers

( -- Going on a diet can be good for you. And maybe a gasoline "diet" of traditional fuel blended with increased levels of ethanol will be good for the environment and economy without hurting cars and small engines. Researchers are trying to find out because new ethanol blends could play a starring role in reducing petroleum use.

The Energy Independence and Security Act of 2007 (PDF 821 KB) (EISA) is one force behind the quest for higher blends. The 2007 law requires that the U.S. use 36 billion gallons of renewable fuels by 2022. But, a leaner benchmark is just around the corner, with 15 billion gallons required by 2012. "We're pushed right now to find ways to get more ethanol into the fuel stream," said Keith Knoll, senior project leader for National Renewable Energy Laboratory's Fuels Performance Group.

Currently, ethanol is the most widely used and readily available renewable fuel. As a result, it is a likely candidate to make up a significant chunk of the 36 billion gallons required under EISA. Ethanol as a motor fuel is commonly found in E85, a fuel intended for use only in Flexible Fuel Vehicles (FFVs). Ethanol also is widely used as a 10 percent blend in standard gasoline (E10) to reduce carbon monoxide emissions and smog. But, increasing ethanol from the current 10 percent blend to a proposed blend of E15 or even E20, brings up a whole host of questions and issues.

For instance, E20 is currently not allowed for use in conventional automobiles under the Environmental Protection Agency's (EPA) Clean Air Act. This is where research from NREL and Oak Ridge National Laboratory (ORNL) will play a pivotal role in understanding how blends like E15 and E20 affect vehicles currently in the market. The research is examining whether using higher ethanol blends will have an adverse impact on tailpipe emissions, exhaust temperatures, catalytic converters and engine performance and durability.

Cars Don't Seem to Mind

While NREL and ORNL will be studying mid-level ethanol blends for some time, data from initial tests on small engines and cars was released in October 2008 and updated in February 2009 (PDF 2.6 MB). Follow-up reports addressing other vehicle effects will be issued over the coming year. Generally, the tests have shown no big surprises or short term effects when using greater blends of ethanol in existing cars.

"So far nothing has jumped out at us and vehicles don't show a significant impact with ethanol blends of 15 and 20 percent," Knoll said.

The automobiles used in NREL's test were meant to represent a cross section of cars currently in use. The 16 vehicles ranged from model years 1999 through 2007 with odometers reading from 10,000 to 100,000 miles.

All vehicles in the test experienced some loss in fuel economy, which is expected because ethanol has a lower energy density than gasoline. At the E20 blend level, the average reduction in miles per gallon was 7.7 percent when compared to gasoline only. "Another issue we looked at was whether there would be any unintended consequences on air quality when using the higher blends," Knoll said.

Study results so far have shown that as ethanol increased, tailpipe emissions stayed largely the same. There was no significant change in nitrogen oxides or non-methane organic gas emissions. Carbon monoxide emissions declined for all of the ethanol blends. There were increases in ethanol and acetaldehyde emissions, but these were balanced with reductions in other hydrocarbon air-toxic emissions.

When it came to how catalytic converters reacted to increased ethanol, results depended on how the engine control system regulated the fuel-to-air ratio during high power operation such as heavy accelerations or long hill climbs. Cars that adapted to the increased ethanol during these activities showed no change in catalyst operation — in fact some even ran cooler at higher ethanol blend levels. Seven of the 16 vehicles tested were found to not adapt to higher ethanol blends during high-power operation. For these vehicles, catalyst temperatures increased during power-enrichment, running about 29-35 degrees C (Celsius) higher on E20 compared to gasoline only. The long-term effects of this temperature increase are being investigated in other, ongoing experiments also funded by DOE.

"While these initial results are interesting, the next step is going to be a larger study, with more vehicles, that will look at the long-term effect that ethanol has on catalytic converters and numerous other issues like drivability and engine durability," Knoll said.

A Small Engine Can Get Revved

While engines seem to take the higher ethanol blends in stride, the same can't be said for small non-road engines (SNRE). An April 2009 Chicago Tribune article on this subject painted an eerie picture, "Picture a chain saw calmly idling. But then it suddenly starts spinning on its own as if someone had goosed the throttle."

The Chicago Times article was a creative, but exaggerated take on what was found in the lab. For instance, it was the hand-held trimmers that got a little excited in the lab, however, "small non-road engines may have trouble with higher blends of ethanol," said Knoll. "This is an area where we need more research."

For this phase of the testing NREL and ORNL used 28 SNREs. Small engines don't have the same feedback control system as cars, nor do they have exhaust oxygen sensors. This means the engines can't automatically compensate for the added ethanol. So, small engines using higher ethanol blends tended to run leaner and hotter. The temperatures of the exhaust components, cylinder heads, and cylinders increased. Exhaust temperatures rose by 10 - 50 degrees C when moving from gasoline only to E15 and 20 - 70 degrees C from only to E20.

Back to those lawn trimmers. When running on a higher ethanol blend, three trimmers did show higher idle speeds and sometimes the clutch engaged on its own. However, Knoll thinks this is easily overcome. "Small engines can be designed to handle differences in fuel. While these engines may not handle a 20 percent change in ethanol, most currently run on E10. Future designs could be engineered to operate with whatever ethanol standard we move to."

Don't read too much into the initial tests for both auto and small engines cautioned Knoll, "Although we've got good data, this was a very small sample that is part of a much larger program."

Future Tests and Decisions

The focus for all of this testing is to help policymakers like the EPA evaluate and understand the impact that new ethanol mixes will have on the existing cars that Americans drive every day.

The ethanol industry is currently seeking a waiver from EPA that would allow for widespread use of E15 in all automobile types. Right now, most gas stations across the country already sell blends using 10 percent ethanol.

"I think that for a long-term solution our focus for consumers is on E85," Knoll said. "Right now E85 use is limited because of the few fueling stations that are available and the limited number of flex-fuel vehicles that are on the road. Our research will give policymakers sound technical advice to help them decide the potential that blends like E15 and E20 will have in the marketplace."

Future mid-level ethanol blend studies will take a further look at issues like:

• Emission control
• Fuel system compatibility
• Engine durability
• Evaporative emissions
• Drivability

This research is co-led and co-funded by U.S. Department of Energy's Biomass Program and the Energy Efficiency and Renewable Energy Vehicle Technologies Program with technical support from NREL and ORNL. The team is working closely with representatives from the EPA, U.S. auto manufacturers, companies, oil companies and Battelle Memorial Institute to develop and conduct a robust test program.

Source: National Renewable Energy Laboratory, by Heather Lammers

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Sep 19, 2009
The EISA (2007) is clearly an oil industry inspired piece of legislation designed to impede the incursion of alternative fuels into their market.
The trial you report is in my view questionable.
All you need do is to travel to Brazil.
Examine the atmosphere in their two mega cities where their cars run on 100% ethanol.

The proof is already out there.
Why not look at it.

It would appear that the research you have reported could have been funded by the oil industry in the hope of creating doubt.

Sep 19, 2009
I highly doubt that this is some oil-based con palmed off onto the public. Fuel efficiency does drop off when using Ethanol in vehicles designed specifically for fossil fuels. My current vehicle states on the lid of the gasoline port to use "Premium gasoline ONLY."

I found after considerable testing that the manufacturer was not kidding. Not only did fuel efficiency drop but my oil looked really nasty after a shorter time. In my wife's flex-fuel vehicle the tank is larger to accommodate efficiency loss when using E85.

I also plan to do further experimentation but so far I am not happy with the results I have seen and had to return to using straight gasoline when making long distance trips--with the exception of Plains States that add 10% Ethanol to nearly all their gasoline.

Sadly, with my last long-distance driving experiment, fuel efficiency suffered while in the Plains states, which meant that I had to refuel more frequently than on previous straight runs on straight gasoline.

Sep 19, 2009
Ethanol is a disaster. Any form of advocacy is stupid. We subsidize it about $1.15/gallon, including agriculture subsidies. It attains little or no net benefit in energy increase, because farming and distilling are very energy intensive. It gets poorer mileage. It ruins gas tanks when they sit idle for weeks, like boats and snow blowers, because of water in alcohol. It has driven up US food prices by 10%, which will go to 30% when we triple the ethanol program size. Ethanol sucks. Kill it. Drill, drill, drill. Use LNG, which costs about 1/5 as much per btu.

Sep 19, 2009
The key to fuel efficiency is getting rid of that 160 year old 4 stroke engine invention.

Sep 19, 2009
Another key for us is to find a way to prevent water absorption in standing Ethanol. It is the water that leads to problems in the tank and fuel system. Unfortunately, there is not a lot we can do about inefficiency as compared with fossil fuels. There simply are not the same amount of carbons in the molecules. CNG has even less carbons but it is true that it is cheaper by far than Ethanol.

Seriously, when we compare the main ingredient in gasoline (Octane the chemical not the other use of the term), C8H18, with Ethanol, C2H6O, and CNG, CH4, the clear winner in terms of available energy per molecule is Octane in the gasoline.

But, if we are going to use ethanol, we should use cane sugar based ethanol rather than corn ethanol. At least cane sugar ethanol is regarded as virtually carbon neutral!

Sep 20, 2009
When my brother put ethanol in his flex fuel truck the mileage was very poor. Even at a much lower cost per gallon it was not worth using. Ethanol is the result of the farm lobby and dumb policy.

Electric cars people.

Sep 20, 2009
This comment has been removed by a moderator.

Sep 20, 2009
While I like the thought of an electric car (notwithstanding use of an electric grid and its inherent problems), I do not like the idea of being stranded on a long distance run when I cannot find a charger between points in journey to my destination. These vehicles simply do not go the distance--yet.

Sep 21, 2009
I do not find NREL's mpg changes for E20 to be true in any of my vehicles except for an FFV Taurus in my fleet. For example in my '04 turbo (which calls for premium) the mpgs for E0 premium ave 31.8, E20 ave 31.8, and E27 ave 31.7. Some FFV's like the Taurus do seem to follow the NREL findings while other like the Impala's follow more along the lines of Minnesota's study. In any case E85 here costs 20-30% less and the FFV's we run in our fleet consume 18-22% more gallons thus the cost per mile is less running E85. Where E85 in an FFV might not pay the consumer is a short trip type run cycle in close to oil production areas.
While Iso-octane is a buy on a the basis stated farther above- there is not much of it in gasoline today.
I like the flexibility that ethanol brings that CNG, electricity, and even gasoline (long term) do not provide by themselves. No one fuel will rule the future- that is what we are suffering from now- we need many choices for the future.

Sep 21, 2009
We use E85 in our 2003 Flex Fuel Vehicle, and the fuel economy decreases from 10% to 20%; most often 15%. I highly doubt the 7.7% decrease with E20 that NREL finds, but whatever. The fact is that we cannot continue with importing foreign petroleum. Each marginal (next) gallon of petroleum comes from farther under ground, costs more to get to, or comes from far higher polluting and costly tar sands and oil shale. Whereas even corn ethanol is energy positive (1.5 to 2.2 units per fossil fuel unit consumed) and only uses 1/6 of a gallon for each gallon of petroleum used--greatly stretching our transportation fuel supplies. We subsidize petroleum through tax breaks, research grants, and especially military protection of oil sources and shipping lanes; to the tune of 100's of billions of dollars ANNUALLY. Otherwise the oil companies would have to protect these supplies, driving the cost far higher. Subsidization of biofuels is far smaller than subsidization of petroleum.

Sep 22, 2009
It is nice that Kieth Knoll has acknowledged that increased acetaldehyde emissions are off set by other emissions (primarily benzine). This increase in acetaldehydes has been jumped on by ethanol foes to say it is toxic and causes more lung disease. Unless thay have changed their protocol the EPA was not even measuring benzine so no acurate comparison can be made. (Would you rather die from lung disease or cancer?)

What is disapointing is there is no scientific effort to determine what blends actually work best. Those of us who have been experimenting know it is about E30 (E23 min.) Actual thermal efficiencies do not follow theoretical BTU content. Ambient temperature also plays a role so tuning for maximum efficency requires a fuel preheat along with computer adjustments. A lightly modified legacy vehicle can get 20% better MPG on E30 than gasoline (that is a 33% increase in thermal efficiency. But also, I would not use even E10 in a small boat. Where is my consumer choice

Sep 22, 2009
Whereas even corn ethanol is energy positive (1.5 to 2.2 units per fossil fuel unit consumed)

I'd be interested to know where you get these numbers. Because realistic best estimates, from the U.S. ethanol industry itself are 1.3 at the absolute best, many professionals surrounding the industry believe the actual end-user ratio is more like .9.

We need to look elsewhere. Possibly switch grass? Possibly engineer sugar cane to be growable in our Northern latitudes? Possibly algae-diesel? Who knows. But, corn ethanol is not where U.S. will gain energy independence, ever. Never. Sorry, but that is reality.

Sep 22, 2009
Or, we could just wait. If the global warming alarmists are right about all their wild predictions we will be able to grow our own sugar cane in Montana in a few years. :)

Sep 23, 2009
Corn ethanol alone is not the silver bullet- it is though energy positive. I not sure where defunctdiety gets his info but today the turn-key ag to ethanol industry is closer to 1.68 out to 1 btu in due to many improvements in farming and processes in the last 2-3 years (all studies are too old for validity- even the 1.68:1). Furthermore the ethanol btu input is almost all natural gas which is not as flexible as a motor fuel (plus if the input/output ratio is magnified to the positive by ethanol-why not use ethanol over natural gas as a power fuel?). The oil industry was historically 1 btu in= 0.75 to 0.8 out. Their processes too have improved some but the energy cost for oil extraction is getting tougher. Corn ethanol does have it's place but it was wise of legislature to cap it at 15 billion gal to prevent disruption in the grain markets(at least until yields catch up). We do need additional alt energy sources for the long haul- cellulosic, wind, water, nuke, solar, etc.

Sep 23, 2009
I not sure where defunctdiety gets his info...

It was a figure from a 2007 National Geographic article, so of course I won't claim improvements haven't been made, but even pursuing it -at this point- is ultimately a waste of resources, because there's so many other options with SO much more potential that won't negatively effect world food markets.

Sep 28, 2009
If adding ethanol to gasoline decreases fuel economy, how is this better for the environment by burning more fuel to go the same distance?

Sep 28, 2009
If adding ethanol to gasoline decreases fuel economy, how is this better for the environment by burning more fuel to go the same distance?

That is where the comparison of molecular formulae comes in.

The main ingredient of gasoline/petrol: C8H18.

The main ingredient of Ethanol: C2H6O.

Gasoline contains additional chemicals that contain chemicals with as high as 24 carbons per molecule.

Fact is, less CO2 is produced in spite of more frequent refills. This is regarded even more so the case with Ethanol made from sugar cane than with corn, sugar cane ethanol being regarded as carbon neutral because of the amount of CO2 absorbed by the sugar cane when growing.

But, notwithstanding, Ethanol in a combustion engine still produces pollutants, even if in reduced amounts.

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