Lee Devlin's Weblog

There's probably no topic more important to those of us who fly General Aviation aircraft than the continued availability of aviation fuel. For those of you who may not be familiar with aviation, the fuel used in aircraft is made the old fashioned way because it uses tetraethyl lead to increase the octane rating. High octane fuel is necessary because about 30% of the aviation fleet use high compression engines, and those aircraft use 70% of the aviation fuel. The engine I'll be putting in my Cozy MKIV will require this fuel. Leaded fuel has been outlawed by the EPA for all other uses, but aviation fuel got an exemption for a period of 30 years. That period ends in 2010, which is coming up soon.

I agonized over the decision over whether to use a high or low compression engine in the Cozy but I figured that with all the aircraft fleet that need 100LL, there would be some fuel developed that would come to the rescue, possibly an ethanol based biofuel. Of course, with an experimental aircraft, I could always put lower compression pistons in the engine and use autogas, if I had to, but that's not ideal. So I was very excited to hear about this new fuel that is being developed that has so many advantages that it's hard to believe it's true.

I emailed the owner of the company and he responded. That's always a good sign. Not only that, he graciously referred me to his associates on the project if I had any more questions about it. I'm really hoping that these guys are successful. Here's the report I got from Avweb:

New GA Fuel Promises Better Range, Lower Cost

"Not only can our fuel seamlessly replace the aviation industry's standard petroleum fuel [100LL], it can outperform it," says John Rusek, a professor at Purdue University and co-founder of Swift Enterprises. The company recently unveiled a new general aviation fuel that it says will be less expensive, more fuel-efficient and environmentally friendlier than any on the market. Unlike other alternative fuels, Rusek said, SwiftFuel is made of synthetic hydrocarbons that are derived from biomass, and it can provide an effective range greater than 100LL, while costing about half as much to produce. "Our fuel should not be confused with first-generation biofuels like E-85 [85 percent ethanol], which don't compete well right now with petroleum," Rusek said. Patented technology can produce the 1.8 million gallons per day of fuel used by GA in the U.S. by using just 5 percent of the existing biofuel plant infrastructure, the company said.

The synthetic fuel is 15 to 20 percent more fuel-efficient, has no sulfur emissions, requires no stabilizers, has a 30-degree lower freezing point than 100LL, introduces no new carbon emissions, and is lead-free, Rusek said. In addition, he said, the components of the fuel can be formulated into a replacement for jet/turbine fuels. The company now is working with the FAA to evaluate the fuel.

Labels: aviation, energy, ethanol

My friend Peter asked if I would write about the amount of water it takes to produce a gallon of ethanol. I have often heard this figure to be quoted at 1000 gallons of water per gallon of ethanol. I wasn't sure how accurate this was, so I started doing some investigation. I found that I live in a county in Colorado that has the most irrigated acres of any of Colorado's 63 counties, accounting for 11% of the state's total. I found that corn requires a moderate amount of irrigation as far as crops go, about 16.5 inches per year in my county. Alfalfa has the highest watering requirements or about 23 inches and melons only require about 8 inches annually. When you compare irrigation requirements with Colorado's average rainfall of 15.5 inches per year, it is obvious that more than half of the corn's water requirements must come from irrigation and this is even more apparent when you consider that corn only grows for 3 months out of the year and during those months, the rainfall total is only about 5 or 6 inches.

Some of the irrigation is provided through surface canals fed by mountain runoff and some is from center pivot irrigation which brings water up from deep wells. I will calculate the energy cost per acre of using a center pivot irrigator assuming a 200-foot deep well and a 50 psi pressure at the pivot's center.

Since an acre is 43,560 sq ft. and we need to apply 16.5" of water to it during the corn growing season, this comes out to 59,895 cu. ft. or 497,128 gallons of water per acre. Last year's average Colorado irrigated corn yield was 189 bushels/acre and the average conversion rate is 2.7 gallons of ethanol per bushel of corn. So the ethanol yield per acre is 456 gallons. Dividing that into 497,128 shows that the number of gallons of water to produce a gallon of ethanol in Colorado is around 1100. This seems quite substantial. Colorado has a very dry climate where virtually no crops can grow without irrigation. In most of the corn belt states like Iowa and Illinois, the average rainfall is closer to 40 inches per year, and so irrigation shouldn't be necessary and thus even though it may take just as much water to grow corn as it would in Colorado, the rain will fall whether you're growing grass, or forest, or corn, so I don't think that the amount of water consumption is as much of a concern as it is in states like Colorado where water is considered a scarce resource.

I mentioned I'd also do the energy calculation for lifting the water from a 200 foot well. 497,128 gallons of water weigh about 4.1 million lbs. and lifting that much water 200 feet and maintaining 50 psi at the center pivot would require 1300 M ft-lbs of energy. This is equivalent to 490 kWh. Derating for a pumping efficiency of 65% we can estimate it would require about 760 kWh in electricity consumption per acre at a cost of $76/acre using $.10/kWh for the electricity rate. With corn selling for around $4.60/bushel, this accounts for about 9% of the value of the corn. So spending $76/acre seems like a reasonable trade-off considering that without irrigation, the corn yield in Colorado would be close to nothing.

Water is the most renewable of all natural resources but sometimes it's treated like it's a scarce or even endangered resource. The stuff does literally fall from the sky. So I guess it all depends on one's situation as to whether water is scarce or plentiful. If you are in the middle of a flood, water is anything but scarce, yet if you're dying of thirst, it can be more precious than gold.

Is it worth 1000 gallons of water to produce 1 gallon of ethanol? Again it depends on one's perspective. If you need to drive a car for 20 miles, 1000 gallons of water will be of no help, but a gallon of ethanol certainly would be. And in the majority of corn-growing states, not planting corn on the land will not prevent rain from falling on it so there'd be no real water savings.

Labels: energy, ethanol

I recently received a pointer to this blog article which references a NY Times piece about articles in Science that state that biofuels actually increase global warming by pulling land into the agricultural pool that was previously a carbon sink. The first of these Science papers is focused on the ethanol industry in the U.S.

During the past 14 years, 15 separate studies have shown that ethanol has a net positive energy balance. Only one study has contradicted it, but the researchers of that study (Pimental and Patzek) wrote the same paper 4 times so you may hear that the ratio is 15:4. It’s the one that always gets quoted (usually unknowingly) when someone tells you it takes more energy to produce a gallon of ethanol than you can get out of it. Now it appears ethanol opponents will have another study to quote, this time about biofuels creating additional greenhouse gases.

In looking in the supporting materials in Science Express, I found this curious assertion:

If corn-based ethanol could not receive a credit for removing carbon from the atmosphere – deleting the feedstock uptake credit from the GREET model-- it would increase greenhouse gas emissions by 48%. It follows that if the use of land to grow corn for ethanol has the net effect of reducing land-based carbon sequestration, the overall effect will be a bigger release of greenhouse gasses.

In other words, they are stating that when comparing greenhouse gases from corn to gasoline, corn should not get a credit for having removed carbon from the atmosphere. Instead they think it should be compared to growing a forest or prairie in the place of farmland which would allow the carbon to be sequestered year after year. Forests and prairies give back carbon to the atmosphere every year when their leaves and grasses die. In the case of forests, every few decades the trees die, or burn, or are used for some other purpose and thus also give back their carbon in a brief instant of geological time. Unless you’re burying the carbon deep under the earth’s surface or oceans, any carbon taken in by plants is given off in a few months or decades. Soils also have a limited capacity to hold carbon and eventually reach a homeostasis after only a few decades. So I consider the logic used in this study to be flawed.

But I will expect that every biofuel opponent will quote it with abandon, never realizing that the authors of the paper are not comparing biofuels with fossil fuels, but rather biofuels with some imaginary state of affairs where forests that capture but do not release carbon to the atmosphere have been replaced by farmland.

All land capable of sustaining plants, whether it be used for farming, prairie, or forest eventually reaches a homeostasis when it comes to CO2 sequestration. Farming allows us to take advantage of the CO2 to carbohydrate conversion that occurs on land whereas prairies and rainforest that go unharvested do not. But in the end, they all return CO2 back to the atmosphere in a relatively short span of geological time. The only counter-examples are swamps that can, over the course of millions of years, turn vegetation into coal by trapping a tiny percentage of carbon each year.

Labels: energy, ethanol

Last week I toured the Front Range Energy ethanol plant in Windsor along with 9 other members of the Northern Colorado Clean Energy Network many of whom are also members of the Northern Colorado Renewable Energy Society. I had requested the tour because I had a desire to see this facility up close to find out what is involved in an operation capable of producing 40 million gallons of ethanol per year. The company manager, Dan R. Sanders, and FRE employees very graciously set up a tour for our group and explained the details of ethanol production at the facility.

Ethanol has been an additive in auto fuels in the U.S. for many years. In addition to making the gasoline burn cleaner, ethanol increases the fuel’s octane rating and helps reduce our dependence on imported gasoline by more than 5 billion gallons per year. While this is still a small percentage of the U.S. consumption rate of 140 billion gallons of gasoline each year, its recent growth rate is impressive as is the rate of ethanol plant expansion and construction. I’ve written about E85 ethanol previously, including using it in vehicles that were not designed for it as well as in aircraft.

I am aware that ethanol is still controversial in some circles primarily due to some persistent myths such as it taking more energy to produce a gallon of ethanol than it returns, which is not true. Ethanol production in this country provides 40% more energy than it requires to produce it and that number continues to improve, but more importantly, ethanol's energy has 3 times the value to consumers than the type of energy it uses, which is usually natural gas. When it comes to energy, some types of energy are worth much more than others because of convenience or compatibility with existing infrastructure. It’s the reason you probably don’t heat your house with coal, even though it’s the cheapest fuel per BTU by a significant margin.

The Front Range Energy plant was built in 2005 and began producing ethanol in 2006. Our tour included a 35 minute presentation to describe the operation in detail by Amanda Huber, the process manager, who walked us through each step in the highly automated process of converting corn into ethanol. She also answered many questions from our members. We were then taken through the facility by the company manager to see and hear all the equipment up close. The words that come to mind to describe the plant’s equipment are large, loud, and highly automated. There are many large cylindrical tanks connected with numerous pipes and pumps. The smell of the plant reminded me of the smell of our kitchen when we make pizza dough.

The corn arrives to the plant by both truck and rail and is stored in two impressively large 500,000 bushel storage silos. The corn from local growers arrives by truck and the corn from outside the region, primarily Nebraska, arrives by train. From the storage silos, the corn moves by conveyor to the hammer mills where flailing hammers pound the dried kernels through screens containing holes that will only allow particles smaller than about 1/10 of an inch to pass. This helps to expose the starch inside the kernel, which accounts for about 65% of the corn by weight. From the hammer mills, the corn passes to the slurry blender which mixes it with water and enzymes and cooks for several hours. It is inside this slurry cooker that enzymes begin to break the corn starches down into fermentable sugars.

From the slurry cooker, the mixture passes through some liquefaction stages and then on to one of four 535,000-gallon fermentation tanks. Additional enzymes and yeast are added to the mash, as it’s called at this stage, and it is allowed to ferment for about 50 hours. This stage is critical to monitor because it’s where the sugars are converted to alcohol and if this process is not properly controlled, it could ruin the entire batch. They use a combination of analytical instrumentation to monitor the health of the yeast as well as the concentrations of sugar, alcohol, and acids in this tank. After the fermentation step is complete, the mixture will contain somewhere between 15-18% alcohol. Another output of the fermenters is carbon dioxide which could be vented to the atmosphere, but in this plant it is fed directly to another plant that condenses it and provides it to bottling plants for carbonating drinks and for making other CO2 products such as dry ice.

The mix is moved from the fermenters to a 735,000 gallon beer well which feeds the distillers. Using a combination of heat and vacuum, the alcohol is separated from the rest of the mix using a beer column to produce alcohol in a 70% concentration and then it is transferred to a rectifier column to get the concentration to 95%. Alcohol and water form an azeotrope at this concentration, meaning that distillation can no longer further separate the water and alcohol. So the next stage is to run the mixture through a molecular sieve to remove the remaining water and produce anhydrous ethanol. The ethanol is then denatured to make it unfit for human consumption by mixing it with about 5% gasoline. It is then pumped into one of two 500,000 gallon tanks where it awaits transportation by truck or rail car to its destination.

From the bottoms of the distillation towers, the solids and water are pumped to a centrifuge which separates the water from the solids. The solids then become wet distiller’s grain which is used as an animal feed. In some plants, this grain needs to be dried so that it will not spoil during transportation and storage, but in northern Colorado, because of its proximity to numerous cattle feedlots and dairies, it can be shipped in its moist state directly to the dairies and feedlots. Trucks remove approximately 1100 tons of this material a day from the plant. If the distiller’s grain had to be dried, it would more than double the amount of natural gas consumed by the plant, so there is definitely a benefit to having large meat packing and dairy industries nearby.

I have simplified my description of this process considerably. There are many auxiliary steps to achieve a high level of efficiency for the plant. For example, there are steps for adding nitrogen to the fermenters, recycling the water, regenerating the molecular sieve, extracting and remixing syrup with the grain, and recovering alcohol which I did not mention. This plant has a lot of very sophisticated and finely-controlled processes. If you’d like to see a little more detail, there is an explanation complete with a diagram at the ICM website, the company that designed and built the FRE plant.

As an engineer, one area I found particularly fascinating was the control room which had a series of computer screens that showed a pictorial view of the real-time status of every level, temperature, flow, and pressure of the entire process from beginning to end, all being monitored by one person. The plant is so automated that it can be run by as few as 3 people. The plant only requires 32 full time employees to run a 24-hour a day, 365-day per year schedule. The plant is able to process 55,000 bushels of corn into 145,000 gallons of ethanol every day of the week and have minimal plant downtime, typically less than 7 days over the course of a year. The plant achieves a yield of 2.7 gallons of ethanol per bushel of corn.

I was curious to know how close to the nameplate value this plant was producing. I had interpreted the nameplate value to be the maximum output if everything ran perfectly every hour of the year. I was very impressed that the plant regularly exceeds the 40M gallon per year nameplate value by more than 20%. So, unlike power generating plants, an ethanol plant has a conservative nameplate value to take into consideration issues that may cause periodic downtime.

Another thing that impressed me was how aware the company manager was of power consumption in the plant. At this plant, a gallon of ethanol requires 15,000 BTU in natural gas and .5 kWh of electric energy. Since ethanol contains 76,300 BTU per gallon of thermal energy, and .5kWh is equal about 1600 BTUs, the excess energy is about 60,000 BTU per gallon.

There is a controversial study by Pimentel and Patzek that is referenced frequently by skeptics about how ethanol has a negative energy balance of 20% meaning that it takes 20% more energy to produce ethanol that it delivers as fuel. However, two separate USDA studies contradict that study, the most recent one showing a 40% net positive energy balance. Yet the numbers the USDA uses, often called ‘optimistic’ by critics, are not as high as the actual numbers from this operating plant. For example, the USDA cites portion of energy attributed to the ethanol plant as 49,700 BTU/gallon. Yet here is an actual plant using only 16,600 BTU in combined natural gas and electricity per gallon. Even if they had to dry the distiller’s grain, they’d still be under 34,000 BTU/gallon. So I don’t think that the USDA study is overly optimistic. It seems to me to be very conservative.

And, like I mentioned before, energy balance is only part of the equation. The cost per BTU of various forms of energy vary significantly so if you take one type of energy that is worth $7/MBTU, such as natural gas, and covert it into energy that is worth $23/MBTU, such as automotive fuel, then energy balance is overshadowed by the net increase in economic value of the energy.

I got a lot of positive feedback from the rest of the members about the plant tour. It was a great to have a chance to see firsthand how ethanol is made. We really appreciated the professionalism and hospitality shown to us by the knowledgeable staff at the Front Range Energy plant.

Labels: energy, ethanol

I previously wrote about using ethanol as an aviation fuel. After noticing that the national average for aviation fuel is now around $4.60/gallon, and E85 is available for $2.19/gallon, it seems fitting to revisit the subject. As oil heads toward $100/barrel, pushing regular gasoline over $3/gallon again it would seem that E85 is poised see some renewed interest at the fuel pumps around the country.

In order to take advantage of E85’s lower pricing in comparison to gasoline, it requires that you have a ‘flex-fuel’ vehicle that is approved for use with E85…or does it? I began to ponder the question of whether you can safely run E85 in a vehicle that is not specifically designed for it. I decided to do some research and experimentation on the subject. There is a lot of misinformation floating around about ethanol, much of it by people who don’t have the slightest understanding of fuel chemistry. It’s sometimes so often repeated that you have to wonder if there is some sort of conspiracy against ethanol. I have a little more experience than the average man off the street about gasoline and ethanol. I worked in HP’s Chemical Analysis group for 7 years (now part of Agilent Technologies) where one of the instruments I helped to design and support measured oxygenate content in gasoline. So I am constantly amazed at how people with no technical background in the subject will confidently repeat common myths about ethanol. I covered a few of those in the aviation fuel article so I won’t repeat them here.

I was interested to know if anyone had developed a kit to convert a conventional car into an E85 flex fuel vehicle. I found that there are several conversion products on the market that splice into a car’s fuel injection system that allow any fuel-injected vehicle to use E85 fuel. Just about all cars manufactured in the past 15 years use fuel injection systems instead of carburetors to adjust the air-to-fuel ratio to the engine. The advantage of fuel injection is that it can be computer-controlled to vary the air-to-fuel ratio based on a number of factors such as throttle position, engine speed, manifold pressure, engine temperature, and oxygen content of the car’s exhaust. The ability to monitor all of these parameters and adjust the mixture accordingly has helped significantly with advances in fuel economy and emissions reductions. The computer is able to adjust the fuel amount by pulsing the fuel injection valves to allow just the right amount of fuel to enter the intake manifold. The air-to-fuel ratio is thus determined by how many milliseconds the injector valve is opened each cycle. By monitoring the oxygen content in the exhaust, it’s possible to tell whether the fuel injectors are providing too much fuel (too rich a mixture) or too little fuel (too lean a mixture) and that information can be used to help close this control loop. Although I haven’t been able to find any technical descriptions on the theory of operation of these conversion devices, the only thing that one can assume that they do is to stretch the pulse generated by the car’s computer to compensate for the air-to-fuel ratio difference required by E85 to extend it beyond what the car’s computer had included in the lookup table for the air-to-fuel ratio settings. It needs to do this because the air-to-fuel ratio for ethanol is about 30% lower than it is for gasoline. So the effect of adding one of these devices to your car is to shift the lookup table to favor E85 fuel in the event that the standard lookup table cannot reach the lower air-to-fuel ratio required to keep the mixture rich enough when running ethanol.

I would estimate that the cost of the electrical components to implement a simple scheme like this would be well under $50, and so you would think a conversion kit would sell for somewhere around $150 or less, but they are charging as much as $500 to $750, which is more that I wanted spend to run some E85 experiments. So I won’t be discussing the efficacy of E85 conversion kits. Instead, I will concentrate on blending ethanol with gasoline at the pump.

Ethanol has about 28% less thermal energy (measured in BTUs) than gasoline. However, the process to convert the BTUs into mechanical energy on cars is rather inefficient, usually less than 30%. Thus it doesn’t automatically follow that your fuel economy will be reduced by exactly 28% when you run E85 in place of gasoline if you can improve the conversion efficiency. In fact, E85 may deliver similar fuel mileage if your car’s computer can advance the timing of the ignition and convert more of the BTUs into usable mechanical energy. This is possible due to ethanol’s superior octane rating, which is a measure of resistance to engine knocking, also known as ‘pinging’ or detonation.

E85 has a 105 octane rating, which exceeds the octane rating of even the most expensive premium gasoline by a wide margin. For example, in Colorado we have 3 commonly available grades of fuel: 85 octane, 87 octane, and 91 octane. These are lower than what you’d find at sea level because at Colorado’s higher altitudes, the risk of detonation is lower and thus you can safely use lower octane fuels

Gasoline’s price goes up with increased octane rating because of its higher ‘grade’ and to cover the expense of the blending agents required to enhance the octane rating. I’ve noticed that the price goes up approximately 7% per grade here in Colorado. I’ve often wanted to use 85-octane gasoline since that’s the lowest price for fuel advertised on the gas station signs, but I know how destructive detonation can be to an engine, so I always use at least 87 grade on my Dodge Durango. On the few occasions I tried 85 octane, I could hear the tell tale signs of knocking when climbing hills. The knocking goes away in a few seconds since the computer is able to monitor a ‘knock sensor’ on the engine and retard the ignition timing accordingly but I still don’t like to hear that sound so I stick with 87 or higher octane.

I noticed that there is a rather extensive Wikipedia article dedicated to using E85 in standard engines. Although there are a number of warnings about all the things that could happen when running E85 in a vehicle not specifically designed to run on E85, most of them don’t apply to vehicles manufactured after 1990. For example, much of the rubber seal material in automotive fuel systems was changed after ethanol became a common blending agent. Ethanol is typically mixed at the rate of 10% ethanol to 90% gasoline to help reduce emissions, and most cars can run fine on a mixture with as much as 20% ethanol. I became curious to see what would happen if I tried running on 30% ethanol, so lately I’ve been filling my tank with 2/3 of the less expensive 85 octane gasoline mixed with 1/3 of E85. This gives me something close to a 30% ethanol ratio (E30) with an expected octane rating of around 91 and a BTU content that would be 90% that of gasoline. Since I’m saving 7% per gallon on the gasoline, and 30% per gallon on the E85, my fuel bill effectively is reduced by about 15%.

I have a fuel computer in my Durango that gives me instantaneous and average MPG and I’ve noticed about a 10% drop in MPG on my E30 blend, so it’s still about 5% cheaper to do this than to fill up with regular gas.

I’m not blending my own E30 for the savings, but rather to satisfy a curiosity about using ethanol. I suppose if one is of a mindset to reduce our nation’s dependence on fossil fuels, blending in E85 at the pump could have an immediate impact of reducing our demand for gasoline by about 30%, or 40 billion gallons per year while increasing the demand for ethanol by a similar amount. The ethanol industry doesn’t produce enough to satisfy this level of demand yet, but if more people started blending E85 with regular gasoline at the pump it may help to drive demand for E85 to help to increase its availability. One of the common shortcomings of E85 is the fact that it's only available in a relatively small number of locations. For example, in my own town of about 77,000 people, we have only two stations that carry it.

What I’d really like to do is reprogram my car’s computer, often referred to as the ECU (engine control unit) or PCM (powertrain control module), to accommodate E85. However, the information to do something like this isn’t readily available. If you're an automotive engineer with Daimler-Chrysler and know how to reprogram the ECUs to be E85 compatible, please contact me ;-).

My nephew is currently in the process of installing an open source-based ECU called a MicroSquirt II in his 1981 DeLorean and I have become his technical support hotline, giving him tips on proper soldering techniques and electronic debugging issues with the device. The more I read about it, the more I like the idea of a completely user accessible and reprogrammable ECU. That would make it easy to experiment with various ethanol ratios and once it’s debugged, the data could easily be made available to anyone with a similar vehicle who wants it.

The EPA is concerned about aftermarket products in this category, of course, because the ECU is largely responsible for keeping the tailpipe emissions compliant with clean air regulations. But I see that as a relatively easy problem to solve because using oxygenated fuels such as alcohol and reducing tailpipe emissions tend to be mutually compatible goals. The EPA has issued laws against altering the ECU in a way that makes the vehicle non-compliant with clean air standards. This was a problem when people were converting cars to run on propane and natural gas back during the first energy crunch but today I think those laws are mainly aimed at companies selling ‘performance chips’ which tend to sacrifice fuel economy and tailpipe emissions for more power.

It will be interesting to see what happens with E85 because the stock market seems to be predicting a glut of ethanol in the near future, but with the recent increase in gas prices it may take care of any potential ethanol over supplies, especially if the idea of using it in standard vehicles becomes popular.

Labels: energy, ethanol

A few months ago I bought an engine for the Cozy that is a 200 HP version of the Lycoming IO-360. This engine produces about 20 HP more the standard 180 HP O-360 engine. In order to get to 200 HP, it has higher compression ratio and that requires the use of 100 octane fuel. Today, 100 octane fuel is available at most U.S. airports, but I worried about its continued availability in the future. Aviation fuel, or 100LL as it's called, uses tetraethyl lead to increase the octane rating of fuel. Adding lead to auto fuel to enhance its octane used to be quite common but fell out of favor when it was found to distribute the lead, now recognized as a poison, into the atmosphere. Just about all countries in the world have discontinued the use of lead as an octane enhancer for auto fuel.

I began to wonder what I might use for fuel in the future should leaded aviation fuel be outlawed, and my attention turned toward alcohol, ethyl alcohol, to be specific. It's also called ethanol or grain alcohol and is used as an octane enhancer. It also makes gasoline burn more cleanly. Ethanol is the form of alcohol that you find in alcoholic drinks. Because of this, it is subject to liquor taxes. The only way to avoid paying liquor taxes is to add poison to it. If fuel was drinkable and available for a few dollars per gallon, it's assumed that no one would bother buying beer, wine, or spirits. With that logic, it's hard to understand why anyone would buy an 18-year-old bottle of scotch for $75 when Everclear can be had for $10. :-) This poisoning is called 'denaturing' and as long as it makes the alcohol undrinkable, just about anything can be used.

It's not unusual for auto fuel in the U.S. to contain 10% alcohol since most cars can run on fuel with this concentration of alcohol. It's beginning to become available at 85% concentrations, called E85, but that requires that the fuel system is compatible with that level of alcohol concentration. Only a small number of vehicles manufactured over the past 10 years or so claim compatibilty with E85 and you can look up whether yours is compatible by searching for "E85 compatibility" on the Internet. Each year, more vehicles are introduced that will run on E85 or regular gasoline and these are referred to as 'flexible-fuel' vehicles. There's even an effort underway to make an aviation grade ethanol called AGE-85.

Back in the 1980s and 1990s when aviation fuel cost about twice as much per gallon as auto fuel, several efforts to qualify auto fuel in aircraft were conducted. They were targeted at older aircraft with low compression engines which were able to run on an aviation fuel called 80LL whose octane rating was close to regular unleaded auto gas. Quite a few aircraft were eligible to burn auto fuel, provided they purchased a placard called an 'STC' for about $200. Some airports actually began carrying it as a less expensive alternative to 100LL after 80LL went out of production. However, the tests to get approval for the STC were conducted before alcohol became a common additive to auto fuel. After it became commonplace to use alcohol as an additive, it was found that some aircraft had problems with it attacking the rubber seal materials in the fuel system. The entities that granted the STC, namely Peterson Aviation and the EAA, do not allow the use of auto fuel that contains alcohol. The octane enhancer of choice back in the 1980's was MTBE, methyl teriary butyl ether, and it had no issues with fuel system compatibility. But it has subsequently fallen out of favor because it has environmental and health concerns. It has largely been replaced by ethanol. Adding ethanol has now become so common with auto fuel, and the difference in price between auto fuel and avgas is not as significant as it was in the 1980s so the popularity of using auto fuel in aircraft is beginning to wane.

The IO-360 engine I mentioned earlier would not be a candidate for an auto fuel STC anyway because the octane rating of auto fuel available in the U.S. runs about 85-91 octane which is much too low and would damage an aircraft engine designed to run on 100 octane fuel. To get a fuel that had an octane rating around 100 would require using some additive. Otherwise, engine knock, also known as auto-ignition, would create multiple flame fronts that collide in the engine's cylinders, increasing pressures and temperatures that over stress and damage the engine.

It would appear that a solution to my concern would be to make the plane compatible with ethanol because it has an octane rating of 105. I recall seeing a group of experimental aircraft showing up at Oshkosh for many years now that all run on ethanol. They are known as the Vanguard Squadron and are shown in the image above. I tracked down one of their members, Dick Pearson, and he generously allowed me to pick his brain regarding his experience of using ethanol in an airplane. Dick has nearly 14 years of experience of using ethanol in 2 separate experimental aircraft that he flies as well as that of the other 4 aircraft in the Vanguard Squadron. He is quite a proponent of the fuel. He told me that there is a lot of controversy and misinformation floating around regarding ethanol. For example, there is a persistent belief that the energy that it takes to grow corn and convert it into ethanol exceeds the energy content of the resulting ethanol, giving it a negative energy balance. This is not true. The reason that this misconception persists is because natural gas is often used in the conversion process to provide heat for making alcohol from corn. But there's a good reason for using natural gas for heat. The value of natural gas per BTU is much lower than it is for ethanol per BTU. It's about a third the cost per BTU as ethanol. So even though one could use a portion of the ethanol to provide heat in the process that makes it, it's not as economical as using natural gas for heat. It's this business of using a fuel other than ethanol to help make ethanol that leads people to believe that it has a negative energy balance. It actually has a positive energy balance widely accepted to be around 1.34, or getting a third more energy out of the process than is put into it. That takes into consideration the energy required to fertilize, plant, irrigate, spray, harvest, transport, and convert the corn into alcohol.

Energy balance is only part of the equation, since when you talk about energy you must consider more factors that the energy balance or cost/BTU. It's also important to consider factors such as energy density, convenience, and fuel compatibility. This is particularly true when it comes to transportation fuels since there is high value to having a fuel that is compatible the existing engines. If energy balance and cost/BTU were the only measures of concern, we might see coal-fueled vehicles since its cost per BTU is about 10% of what we pay for gasoline.

In Brazil where they make alcohol from sugar cane, they are able to burn the waste parts of the sugar cane called bagasse to generate the heat needed for the process. As a result, they get 10 times more energy from the sugar cane than is required to grow and convert the sugar cane to ethanol. This is similar to the energy balance expected with cellulosic alcohol.

A number of companies are working on deriving ethanol from cellulosic plants instead of corn kernels. These materials include waste products such as wood chips, corn and wheat stalks, and other organic waste materials that have limited use today. In most cases, you have to pay someone to dispose of them. The processes that convert cellulose to alcohol are currently not mature enough to be cost competitive with making ethanol from higher-value materials like corn. However, there are a number of companies working to improve the processes and if they become competitive, it could reduce the cost of ethanol to be lower than gasoline in a direct fuel mileage comparison, and when that occurs, it has the potential to change everything.

Some cellulose-to-alcohol processes are based on enzymes that can unlock the sugars in cellulose and convert it into alcohol using conventional fermentation. There is an ethanol plant in Canada already doing this as well as a few more under construction. There is a also a non-fermentation process developed by Range Fuels of Broomfield, Colorado that can convert cellulosic materials to alcohol. Range Fuels is building a cellulose-to-ethanol plant in Georgia that will be capable of producing 100 million gallons of ethanol a year from wood chips. I think this will substantially change the perception that ethanol is nothing but a farm subsidy, which is the view a lot of people have about it today. Can you imagine a lawn service where they reduce the fee if you let them take away the lawn clippings, leaves, and other yard waste? I think that would be a huge step in the direction of energy independence because recovering energy from local waste materials would reduce an energy supply chain that currently extends around the globe to a short loop within your own neighborhood. It would also reduce CO2 emissions because plants generally release their carbon back into the atmosphere in a relatively short time, and so instead of digging up carbon that has been buried for millions of years, we'd be able to use carbon that was essentially on its way back into the atmosphere anyway.

There are a lot of competing and complementary renewable energy technologies under development including wind, solar, and biomass. I don't think that there will be a single winner in the race to replace our convenient yet exhaustible fossil fuels. I feel a lot more optimistic about it after doing my own investigation of alternatives like ethanol instead of listening to pundits arguing for or against it, because it doesn't take long for people to get emotional about their point of view when it comes to renewable energy. I guess that's because mixing politics with science can be such a volatile combination. Now if only that volatility could be converted into usable energy our future would be secure!

Labels: aviation, energy, ethanol