Ethanol's pros and cons

June 19, 2006 11:57 AM

How much does an x% ethanol gasoline blend product reduce mileage? Does the environmental benefit from ethanol blends outweigh the increased consumption of gasoline products? Or is the benefit negligible for the consumer?

Though ethanol burns cleaner, it apparently holds less chemical energy for the same volume. After noticing local gas stations selling (only) 10% ethanol blends at higher prices, I'm curious about how much of an effect this has on mileage. Most of the information I've found (from corn growers) is handwaving, inconclusive or apologetic.

After all, if the fuel burns faster and costs more, and the ethanol supply is subsidized, that means more frequent and profitable repeat business for energy suppliers and corn growing-conglomerates like ADM.

Further, more frequent trips to the gas station mean increased emissions for the same energy dollars spent in the country.

Also, I imagine that ethanol corrosion also means more dollars spent on parts replacement and labor in the automobile maintenance industries, which also has a waste impact on the environment (more stuff put into landfills at a faster rate).

Do the ethanol products have a genuine and pronounced net benefit to the environment or is this about profit for energy, agribusiness and automobile corporations?

posted by Blazecock Pileon to travel & transportation (12 answers total)

Ethanol is blended into gasoline at various concentrations, for a variety of reasons. Among other things, it helps to scavenge water that collects throughout the fuel storage and delivery system, pulling it through in small amounts that burn up in your engine, before the water gums up your tank and fuel line. In blend amounts up to 15%, ethanol also acts as an oxygenator, lowering emissions and supplanting other oxygenator additives such as MTBE.

At high blend levels, such as E-85 flex fuel, where the ethanol becomes the majority of the blend by weight, the net lower energy of the blend does become a factor, and the vehicle will get somewhat lower mileage (maybe 15% lower mileage, as opposed to conventional 87 octane gasoline). But most modern American cars are capable of burning E-85 with no change in calibration, or detriment to fuel system, engine, or anti-pollution system components.
posted by paulsc at 12:11 PM on June 19, 2006

I was just talking about ethanol with my father, who lives in the Corntacular state of Iowa, a leading producer of ethanol. He told me that in many situations, get this, coal is required to burn the corn/biomass to produce the ethanol. Coal. Trucked in from Montana.

I really wish that I could jump on the Ethanol bandwagon, but little facts like this make me think that the issue is at least much more complicated than ethanol producers would like us to know. And somehow I doubt that rosy descriptions of how good ethanol is for the air don't factor in the gas burning trucks hauling that coal from Montana to Iowa, nor the burning of the coal.

Here's to holding out for Hydrogen...
posted by mcstayinskool at 12:17 PM on June 19, 2006

I note about a 10% reduction in mileage betwen 100% gas gas and 10% ethanol gas. This is consistent over two cars, and over multiple seasons.

Given that ethanol has some energy, losing 10% mileage for 10% ethanol implies that there's something else going on. It may be that certain car ECUs are programmed assuming ethanol gas, and others aren't. I don't have nearly enough data.

I suspect that looking at it from a "wellhead" cost point of view, ethanol costs more, but it seems to have emissions advantages which make up for the cost. In particular, ethanol replacing MTBE may be a win all by itself, health wise.
posted by eriko at 12:18 PM on June 19, 2006

Wikipedia answers all your questions, at least regarding energy content.

Ethanol is not particularly good nor bad for the environment. It's a hydrocarbon made from plants, which is exactly what gasoline, oil, natural gas and coal all are. All of these can be burned cleanly or can be burned dirtily. Each produces waste heat and CO2, and each has its own special "extra" pollution - Coal, for example, tends to produce unpleasant sulfur compounds, which end up as acid rain. Ethanol produces aldehydes, which burn human mucus membranes (eyes nose and throat) and cause cancer. There's no free lunch.

The only real advantage is that ethanol can be made in real-time, rather than waiting millions of years.

Converting the U.S. to run on ethanol would require more land be devoting to growing corn than exists in the U.S. So, full conversion is not going to happen in the foreseeable future. Right now the pressure in favor of ethanol in coming mainly from corn farmers seeking subsidies.

The comment above about cars being able to use E85 without modifications is not true, I don't think. Modern cars can use up to 10% blends of ethanol. E85 requires significant engine changes - they have a sensor which detects what sort of fuel the car is using and adjusts the engine accordingly. E85 in a non-capable car would likely damage it. There is a list of E85-capable cars.
posted by jellicle at 12:34 PM on June 19, 2006

There might be something else at work here, but I think I get better gas mileage.

I drive an 02 Ford Focus, and before going on my weekendly 2 and a half hour drive back down to Iowa, I fill up. This is all non-ethanol gas. It generally takes a little over half a tank to get down there, and then I drive around enough to get down to about a quarter of a tank.

Before leaving, generally I fill up with E10, because it's cheapest thanks to subsidies. It varies, but one good week I managed to get back with only using a quarter of a tank, and drove back and forth to work for the rest of the week, finally getting down to under a quarter of a tank on the Friday. This was the best time, other ones had also been only slightly better gas mileage.

I think there may have been things like the wind blowing in a favorable direction, or maybe filling to a different level, or a few other factors, but despite that, there was a definite difference in my gas mileage in E10's favor for me, and not a single bit of a mileage hit.
posted by cellphone at 2:29 PM on June 19, 2006

Converting the U.S. to run on ethanol would require more land be devoting to growing corn than exists in the U.S. So, full conversion is not going to happen in the foreseeable future. Right now the pressure in favor of ethanol in coming mainly from corn farmers seeking subsidies.

On public radio and in various print publications I read, I've been coming across lots of talk about "switch grass" farms, which apparently create ethanol much more efficiently than corn. There seems to be some sort of consensus that corn won't do it, but other crops would be more efficient.
posted by croutonsupafreak at 3:04 PM on June 19, 2006

He told me that in many situations, get this, coal is required to burn the corn/biomass to produce the ethanol. Coal. Trucked in from Montana.

You don't burn anything to produce ethanol, although you do have to heat stuff up to near boiling point. This could be done by burning coal, other ethanol or electricity. It may be that ethanol plats use electricity from coal burning plants, I suppose.
posted by delmoi at 3:14 PM on June 19, 2006

The numbers I've seen quoted are that E85 reduces mileage by up to 30%. That held up when I checked a specific vehicle at fueleconomy.gov.
posted by pmurray63 at 8:42 PM on June 19, 2006

I once worked for a public policy think tank which did a lot of work on ethanol. The question of how much of a net energy gain ethanol is (in essence, how much of its energy as a fuel is derived from the sun) is a very complicated one. There are a few outspoken oponents who hold you end up expending more energy as a fossil fuel than you get from the ethanol. I believe a more informed concensus asserts it is a net energy gain. You can download a PDF of my former employer's most recent assessment here, their work contributed to a study DOE recently did which concluded an average 35% net energy gain. Part of the issue is that the efficiency of making ethanol can vary a great deal from plant to plant (manufacturing plant that is, not, uh, corn). It's only fair to note that PDF is based in research but its intent was certainly advocacy.

Complexity example: Farmer Brown produces 10,000 bushels of corn and a thousand are turned into ethanol. Researcher A tots up all the energy use of the farm and divides them by ten to get the amount of fossil fuels to produce the corn. Fair enough. But researcher B says, look, he would have produced those 9,000 bushels for consumption anyway, the additional energy just needed to produce an extra thousand is much less than 1/10th the total. Life cycle and net energy analysis are relatively young fields; and often the "right" answer is a matter of interpretation.

Ethanol has a few environmental benefits. If you believe it is a net energy gain, it reduces consumption of fossil fuels and because plants derive carbon from CO2, the CO2 produced by burning ethanol is global warming neutral (if you believe in global warming) - but you have to consider those petrochemicals burned to manufacture it again, that is a net CO2 increase. You see how this stuff is. Ethanol is also a fuel oxygenate and as such it reduces polluting emissions. The other widely used oxygenate MTBE has been linked to groundwater contamination so there is another benefit there.

A further issue is that ethanol as a fuel works best where there is a local production and distribution system, so if you're living somewhere where it's being shipped in from relatively far away the benefits of use will be lower and the cost of use higher.

The levels of ethanol in standard automotive fuel blends will not increase wear on your engine, but E85 should not be used in a vehicle not designed for it. There are varying figures on relative efficiency, for example see a fairly sane discussion here, I think for like a 10% blend it is likely in the single digits, 2-5%.

There's no question ADM in particular profits from ethanol subsidy. But then a lot of farmer co-op operations and generally more palatable business interests do as well. Considering all the things our taxes subsidize ethanol probably looks pretty good on the Relative Evil Scale. There's also no question that when you look at all the issues you mention (except engine wear which I think is a myth), the general trend is that they chip away at the benefits of ethanol.

I've read a lot of reports, and I think the bottom line is that ethanol is a net gain environmentally, but one of moderate significance. Using it is a judgement call particularly if it is more costly at the pump. There are business and political interests involved but not terribly malign ones. But I suspect it will be a minor player in fuel history 101 unless we crack efficient cellulose to ethanol. Time will tell.
posted by nanojath at 10:51 PM on June 19, 2006

(that's a 2-5% decrease in fuel efficiency for a 10% ethanol blend)
posted by nanojath at 10:53 PM on June 19, 2006

pileon: Your comment about "more frequent trips to the gas station mean increased emissions" doesn't make a lot of sense to me. I don't think I've ever made a special trip just to buy gas for the car. Doesn't everybody simply refuel their car when they would be driving their car anyways?

mcstayinskool: There may be coal burned in the manufacture of ethanol, but how do you think oil tankers and gasoline tanker trucks travel the globe? What do the oil refineries run on? Fairy dust? Do you want to shuck a cob or corn at the grocery and squeeze auto fuel out of it into your car's tank?

cellphone: I don't want to be a total jerk, but your fuel efficiency anecdote isn't real helpful.
I track my MPG every time I fill up (miles since last fillup / gallons of gas = MPG). It's not scientifically perfect, but with a large enough sample, it should be pretty close.
From April 2005 to June 2006, my 1999 VW Jetta got 27.2 MPG. In June 2006, when the gas stations I use switched to 10% Ethanol, my mileage has dropped to 24.2 MPG. (NOTE: That second number is based on only four tanks of gas). That's a 9.13% reduction in fuel efficency.
posted by Lord Kinbote at 7:36 AM on August 9, 2006

pileon: Your comment about "more frequent trips to the gas station mean increased emissions" doesn't make a lot of sense to me. I don't think I've ever made a special trip just to buy gas for the car. Doesn't everybody simply refuel their car when they would be driving their car anyways?

If you have lower mileage, you have to refuel more often. More trips for the same mileage means more fuel volume consumed, which means increased emissions per mile, all else the same.
posted by Blazecock Pileon at 4:37 PM on August 9, 2006