THE NEED FOR ALTERNATIVE FUELS
Since the 1970s, America's fuel imports have almost tripled. The country is now importing over 12 million barrels of crude oil a day. That's just over half of the oil we are currently using in America -- over 20 million barrels a day. The majority of this fuel is going to power transportation, most of which is used in consumer motor vehicles. The more America increases its dependence on petroleum, the faster oil reserves become depleted. We are only decades away from the point at which there is too little petroleum left to make gasoline a feasible fuel. Americans cringe at .00 per gallon gas prices, but cringe is all we do. We continue to pay the asking price for the only fuel that can make our cars run. But what happens at .00, or .00 per gallon? The rate that gas prices have raised in the past couple years show us that these extremes are chillingly close [1].
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While several fuel alternatives have begun to show promise, they all seem to also have distinct drawbacks. Some fuel alternatives could be too costly to become a commercially viable alternative to gasoline. Other more cost effective fuels do not appear to meet the range of requirements demanded by consumers. Few of these sources currently appear to be capable of matching the energy output of gasoline. Best estimates suggest that within 40 years, crude oil resources will be sufficiently depleted as to render gasoline commercially unviable. It is crucial that we quickly find an acceptable replacement for gasoline.
In addition, it takes no stretch of the imagination to understand what levels of pollution are being created by our nation's oil addiction. One only has to look at the skies above New York City or Los Angeles to see where we have come in past century of automotive transportation. It is easy to see that alternative fuels will be needed very shortly to replace gasoline. Still, it is equally important that the next fuel we rely on does nothing more to pollute the environment. In the best-case scenario, our next national fuel should assist in alleviating our current levels of pollution.
WHY SHOULD ENGINEERS CARE?
Because of the booming industries that alternative fuels are creating, many more engineers will be required for research and development. These engineers will play principle roles in the biggest breakthroughs in alternative fuels in our lifetime. Furthermore, engineers will be needed to design the new infrastructure that will be used for the transportation and delivery of new fuel systems. With this in mind, it is imperative that engineers continue to invest time and intellectual capital to further scientific developments of alternative fuels. The research of today will be the answer of tomorrow.
WHAT ARE OUR OPTIONS?
Research in the field of alternative fuels is a booming industry. There are dozens of potential fuels that show some potential as a viable alternative to fossil fuels. For the purposes of our paper, we will review the six fuels that we believe to have the greatest likelihood of replacing traditional fossil fuels. These are: biodiesel; hydrogen; methanol; ethanol; electricity; and natural gas. Each of these fuels has had extensive testing to demonstrate substantial potential as an answer to America's quest for a replacement of gasoline.
DIMENSIONS OF COMPARISONS
For a credible comparison, it is important that a standardized basis for evaluation be created and applied equally to each of the six fuels. To of this, we will be evaluating the fuels on the following criteria:
-Power output
-Cost and ease of production
-Environmental effects
-Renewability
We have rated each fuel in each of these categories on a scale of 1-10, with 10 being the highest. This will allow quantitative comparison. Renewability is double weighted in our comparison due to its importance in solving the energy crisis in a sustainable manner. Continuing below is a full analysis of these six alternative fuels on the abovementioned dimensions of comparison.
BIODIESEL
Biodiesel is a fuel created from organic oils, such as vegetable or seed oils. The production process uses chemical reactions to create the liquid fuel. Biodiesel is an alternative to petrodiesel and can be substituted for petrodiesel in most diesel engines with little or no modifications to the engine itself. The fuel is already commonly added to diesel fuel in small amounts. B20, a common fuel mixture, is 80% petrodiesel and 20% biodiesel. Many countries already have laws requiring specific percentages of biodiesel additions to petrodiesel [2].
Biodiesel: Power Output
100% pure biodiesel (B100) has a power output of just slightly less than that of standard petrodiesel. B100 has a power rating of 118,296 Btu/gallon, about 8.5% less than petrodiesel's 129,500 Btu/gallon rating. B20 (20% biodiesel) has a power rating only 1.73% less than petrodiesel. Because pure biodiesel has slightly less energy density as compared to its petroleum-based counterpart, a slightly larger volume of biodiesel is required as compared to petrodiesel to travel the same distance [3]. Because of the relative energy density of biodiesel as compared to petroleum-based fuels, we have assigned biodiesel a rating of 7 for power potential.
Biodiesel: Cost of Production
Biodiesel is most commonly and efficiently produced using a process called transesterification. Through transesterification, the alkoxy group of an organic ester compound is replaced by another alcohol, usually methanol or ethanol. The process of creating biodiesel is relatively simple, but not nearly as cheap. Best estimates put B100 at about .50 per gallon [4-5]. Even though .50 is currently comparable to gasoline prices, the efficiency ratio of biodiesel to petroleum fuels must be taken into account. A gallon of biodiesel just doesn't go as far as a gallon of petrodiesel. Therefore, it would cost more to travel a set distance using biodiesel as compared to gasoline. For these reasons, we have assigned biodiesel a value of 5 for cost.
Biodiesel and the Environment
Biodiesel is an environmentally friendly fuel. The liquid fuel itself is biodegradable, and therefore does not pose the risks associated with petroleum based oil spills. Biodiesel is actually 10 times less toxic than regular table salt, which makes the fuel much safer to handle than gasoline.
The combustion of biodiesel produces significantly less harmful emissions than petrodiesel.
Emissions from B100 have reductions of 67% unburned hydrocarbons, 48% less poisonous carbon monoxide and 47% less particulate matter, as compared to gasoline. However, biodiesel has around a 10% increase in nitrogen oxides, which are a large factor in the creation of smog [6]. Because of the reduction in poisonous emissions, we have rated biodiesel an 8 for environmental effects. Biodiesel has many environmental advantages, but the increase in nitrogen oxide emissions has kept us from rating it any higher.
Biodiesel: Renewability
Biodiesel is an excellent example of a renewable resource. The material components used in the creation of biodiesel are entirely organic. In addition, there are hundreds of diverse plant species that have known potential in biodiesel production. As long as there are oil-producing plants in existence, as well as the organic material needed to create alcohol, there will be the means for producing biodiesel. We have therefore given biodiesel a 9 for the category of renewability.
HYDROGEN
Hydrogen powered fuel cells have often been touted by advocates of alternative fuel. In fact, when one thinks of alternative fuel possibilities, often the first image to come to mind is a hydrogen car. However, hydrogen fuel has problems under the surface, which could limit its use as a fuel in the future.
Hydrogen: Power Output
There are two ways to harness energy from hydrogen. The first, and less efficient method is through combustion of hydrogen, similar to the internal combustion of gasoline or diesel. The more efficient use of hydrogen is in a hydrogen fuel cell, in which the hydrogen reacts with oxygen to produce water and electricity. The electricity is then used to power electric motors that propel the car. Through this method, a hydrogen fuel cell would have 25% greater power efficiency than gasoline [7]. Because of this high efficiency, we have rated hydrogen a 9 for power.
Hydrogen: Cost of Production
Hydrogen can be produced in various ways. Most production procedures for hydrogen gas involve fossil fuels such as coal, natural gas and petroleum gas. A more renewable method for creating hydrogen is through a process called electrolysis, which releases hydrogen from water. This is also a much cleaner process for collecting hydrogen [5].
Hydrogen production is prohibitively expensive. To make matters worse, the cheapest method of producing hydrogen is through using fossil fuels. Using renewable resources for hydrogen production is a very inefficient process, around 25% efficiency at best. In addition, fuel cell costs are enormous due to the fragility and the high cost of rare materials, like platinum, which are vital to their construction.
Some non-fuel cell type hydrogen cars are already on the road, thanks to the efforts of a small number of private entities. There are a few small companies that sell custom internal combustion engine hydrogen cars with fees well into the six figures. For example, one start-up company offers to convert a Hummer to hydrogen power via the less efficient internal combustion method for ,000, not including the price of the Hummer [8]. Because of the inefficiency of hydrogen production, as well as the price tag for the fuel alone, we have assigned hydrogen a 3 for cost.
Hydrogen: Environmental Impact
A car running on a hydrogen fuel cell releases no harmful pollutants in its emissions. In fact, the only compound leaving the tailpipe of a hydrogen fuel cell powered car is pure water. As good as this sounds, one needs to asses the 'cradle to grave' effects of hydrogen on the environment. The easiest and most common process for the production of hydrogen, which is through fossil fuels, actually creates more pollution than just running a car on that same fossil fuel. Therefore, a car running on hydrogen would produce more pollutants than a car running on gasoline [7].
On the surface, hydrogen might appear to be the best alternative fuel for the environment. However, it will take a significant technological breakthrough before an efficient process for hydrogen production can be developed to eliminate harmful emissions. Because of the total pollution caused in the hydrogen process, we are rating hydrogen a 4 for the environment. One day there may be an environmentally friendly and cost effective way to produce hydrogen. For now, that day is not in sight.
Hydrogen: Longevity
Hydrogen is a basic and common element on this planet. It will always be around in some form or another, and thus, will always be a possibility for fuel. However, the most common collection processes for hydrogen utilize fossil fuels. This means that there will come a day where the only means for hydrogen production is through the very inefficient and costly renewable process of hydrolysis. At that point, it will be much more advisable to put that energy into more efficient methods of transportation. For these reasons, we rate hydrogen as a 6 for sustainability.
ETHANOL
Over 100 years ago, Henry Ford described ethanol as "The fuel of the future." His famous model T was originally designed to run on pure ethanol. However, because of oil reserves discovered in Texas, ethanol soon took a back seat to the less expensive and better performing petroleum based gasoline. But because ethanol has been used as a fuel for so long, the benefits are well understood. With gasoline's days numbered, ethanol is beginning to look much more attractive, and is one of the front-runners in today's race for alternative fuels [9].
Ethanol: Power Output
Testing shows that ethanol has a lower fuel density than gasoline by about 33%. That means that a car capable of achieving 30 miles per gallon on gasoline would only get 20 miles per gallon using ethanol [10]. However, the production and costs associated with ethanol could help to offset this lack of energy potential. This will be covered in more detail in the next section. We have assigned a value of 5 to ethanol for power output.
Ethanol: Price and Production
Ethanol is most commonly produced in the United States using domestically grown corn in a process where sugars from the plant undergo fermentation with yeast. The process is around 40-50% efficient. However, the amount of farmland needed to grow enough corn to supply our country's fuel needs is enormous. Estimates suggest that about 70% of America's farmland would need to shift to corn production, with the entire crop going to ethanol instead of human consumption or animal feed. While corn is the predominant plant for use in ethanol production in the United States, there are several foreign plants that yield much higher levels of ethanol. For example, Brazilian ethanol production is much more efficient than American ethanol production, as their Brazilian sugar cane produces five times the organic sugars found in corn [5].
While efficient, in certain climates it can be difficult to run a car on 100% pure ethanol because the fuel is not volatile enough to start an engine at low temperatures. To combat this problem, ethanol is often sold as an 85% ethanol and 15% gasoline mixture known as E85. E85 costs about .50 per gallon, though the price will most likely fluctuate as corn prices fluctuate with demand for ethanol [11]. The .50 per gallon figure is already substantially less expensive than gasoline, and the cost margin will only increase as gasoline prices rise. We have rated ethanol a 7 for production and costs.
Ethanol: Effect on the Environment
Ethanol is a small, simple biodegradable molecule and therefore does not pose the same threats as petroleum-based fuels, or the crude oil they are derived from. Ethanol emissions consist of two main products, carbon dioxide and water. While carbon dioxide is not a poisonous gas, it does contribute to global warming through the greenhouse effect. Ethanol combustion however does reduce many of the harmful emissions that are created from gasoline combustion. As compared to gasoline, ethanol creates 40% less carbon monoxide gas, 20% less particulate matter, 10% less smog forming nitrogen oxides, and 80% less sulfate emissions [12].
Even though ethanol combustion emissions are lower in mostly all of the toxic gases found in gasoline emissions, ethanol production releases air pollutants. This has to be factored into the overall environmental effect of ethanol use. All things considered, we have assigned ethanol a 6 for environmental concerns.
Ethanol: Renewability
Ethanol is a good example of a renewable resource. Created from plant sugars and fermented with yeast, the production of ethanol is an organic process that can be repeated as long as these basic biological building blocks are available. So for as long as we can grow corn, we have the ability to produce ethanol. We have rated ethanol as an 8 for renewability.
METHANOL
Methanol is an alcohol fuel similar to ethanol. The fuel is produced primarily from methane gas, which is the chief constituent of the fossil fuel natural gas. Recently though, there has been considerable research into using various forms of biomass to create methanol in a renewable fashion. This would increase the renewable production of methanol.
Methanol: Power Potential
Methanol's energy storage is only about 60% of the energy capacity of gasoline. However, it does have a higher octane rating (123) as compared to premium gasoline (93). This allows for higher compression ratios of the fuel in the engine cylinder, making the fuel burn hotter and more efficiently. Because of the significant difference in potential energy between methanol and gasoline, we have rated methanol a 5 for power potential.
Methanol: Production and Expenses
Methanol is most commonly produced from methane gas, often coming from natural gas. However, it is also possible to produce methanol from a "Biomass-To-Liquid" process using renewable resources with efficiencies reaching 75%. Similar to ethanol, methanol is not sufficiently volatile to ignite at low temperatures, so an 85% methanol and 15% gasoline mixture (M85) has been developed to solve this problem [13].
Methanol currently costs about 40% less than gasoline (assuming a national average of .50 per gallon of gasoline) in equal amounts, but because the fuel is also about 40% less efficient, the price saving is negated. That is to say, .00 will buy a greater volume of methanol, but it will take you about as far as .00 of gasoline. This simply means that for a car to travel as far as one could with gasoline, the same car would have to store a larger volume of methanol onboard [5]. Methanol was assigned a 6 for cost in our rating system.
Methanol: Environmental Concerns
Methanol fuel in its liquid form is extremely poisonous -- four times as toxic as gasoline. Less than a cup is enough to cause blindness or death. The fumes can be inhaled during the pumping process, and methanol can even be absorbed through the skin directly into the bloodstream. The fuel can also be very corrosive to vital engine parts such as hoses and injectors, meaning that a revamping of engine components is required to convert a gasoline powered car to operate on methanol.
Emissions testing of M85 have shown that it does perform well in reducing the toxins produced by gasoline emissions. As compared to gasoline, there is a 36% reduction in nitrogen oxides, 53% reduction in carbon monoxide, and 74% fewer hydrocarbon equivalents [14]. Even though methanol does perform well in emissions testing, the extreme toxicity of the fuel has to be taken into consideration. We have rated methanol as a 5 for environmental safety.
Methanol: Renewability
Because methanol is currently being produced through the use of the fossil fuel natural gas, the process is not renewable. However, there are alternative production methods that use biomass and fermentation to create methanol in a renewable way. The biomass used in this process can even come from consumer waste, such as sewage and landfill gas. Further research needs to be performed to continue to expand the base of materials that can be included in this "Biomass-To-Liquid" process, but at 75% efficiency so far, methanol could become a viable renewable resource [13]. We have assigned methanol a 7 for renewability.
ELECTRIC ENERGY
Electricity powered transportation isn't new. The first electric trolley was built in 1835, with an electric carriage following a few years later. The technology is well know, and constantly improving. In the past two decades, several concept and production cars have been created by large car companies such as GM, Honda and Toyota to demonstrate the feasibility of electric cars. In the future, electric power could be one of the most sustainable alternative fuels [15].
Electric Power
The power of an electric car is directly related to the power of the battery. Battery power is measured in kilowatts, with 100 kW approximately equaling 135 horsepower. Historically electric cars have received criticism for having poor range on one battery charge. Many earlier electric vehicles released in the 1990's had ranges of only 50 or 60 miles on a charge. New innovations in batteries, with the most recent being powerful lithium ion batteries, promise to drastically increase the range of electric vehicles. Some of the newest batteries have storage capabilities of over 120 kW, and can allow a car to travel hundreds of miles. We have rated electricity an 8 for power potential [16].
Cost and Generation of Electricity
Most electricity in the United States is still being produced through coal-fired power plants. However, there is an increasing amount of electrical energy being created through completely renewable resources such as solar, wind and hydropower. Electricity production through electric companies is low cost in the United States. Last year the average price of electricity was under .10 per kWh. The cost of electricity to power electric vehicles is only about 25% of the cost of alternative liquid fuels. In addition, electric motors that are responsible for providing the mechanical power for electric vehicles achieve around 90% efficiency [17]. Because of the high efficiency and low cost of electric power, we are rating it a 9 for production and cost.
Electric Power: Environmental Effects
Electric vehicles produce no emissions. The only emissions created from the electrical process are from the production of electricity. Electricity produced from coal burning power plants continues to release toxic sulfur dioxide and carbon dioxide into the atmosphere. However, when electricity is generated from renewable resources, there are no emissions in either the production process or the use of electricity in the electric vehicles. That means that a car can drive any distance with absolutely no emissions of any kind [5]. Because of the increasing amount of clean electricity being generated as well as the lack of emissions from electrical power, we have rated electricity a 9 for the environment.
Electricity Doesn't Grow on Trees
Electricity still has to be generated in some form or fashion. The best hope for electric cars will be to continue to invest time and resources into research of renewable sources for electrical energy production. Because of the lack of emissions of electric cars, they could pose the best possible replacement for gasoline. It will only require the development of more renewable electric energy to have a completely emission free means of transportation. We rate the renewability of electricity at 9.
NATURAL GAS
Natural gas is another alternative to gasoline that has already seen some use in cars today. Honda created a Civic GX in 2005 that runs on compressed natural gas, and can be refilled at home with a compressor. The fuel itself does indeed represent a viable alternative to gasoline, but there is no disguising the fact that it is still a fossil fuel doomed to extinction [5].
Natural Gas: Power Efficiency
The power generated by natural gas is just below that of gasoline, by approximately 1%. However, the higher octane rating of natural gas (120) allows for higher compression ratios in combustion engines, which contributes more efficient burning of the fuel, and generates more power. This helps to make natural gas combustion slightly cleaner as compared to standard gasoline combustion as well [18]. We have rated natural gas as an 8 for power effic
Natural Gas: Costs and Production
Natural gas can be obtained from several sources. It primarily comes from underground oil fields in either a dissolved or isolated form, but also from its own separate natural gas fields and from coal beds. The gas then goes through a processing plant where several of its natural constituents, such as acids, mercury, sulfur and water are removed. The gas can then be pipelined for delivery.
The cost of natural gas in the United States is currently around .00 per 1000 cubic feet. This is roughly equal to 1 million BTUs. The cost per gallon equivalent to gasoline would put natural gas at about .50 per gallon equivalent [19]. The relative ease of purification and transport of natural gas, combined with the cost equivalent to gasoline leads us to assign natural gas an 8 for production and cost.
Natural Gas: Environmental Aspects
Natural gas has mixed benefits and drawbacks when it comes to emissions. The benefits are that many of the smog and global warming compounds that are generated from gasoline combustion are found in much lower levels in natural gas. To start, natural gas emissions produce about 25% less carbon dioxide levels, 75% less nitrogen oxides, and almost no sulfur or mercury compounds. However, burning natural gas produces slightly higher amounts of carbon monoxide gas than gasoline [18]. All things considered, we have rated natural gas a 7 for environment effects.
Natural Gas: Renewability
There is no escaping the fact that natural gas is a fossil fuel. Once natural gas has been depleted, any engines that ran on natural gas will have to be modified for use with other combustible gases if their use is to be continued. There are no processes known to exist that are capable of producing synthetic natural gas. For this reason, we have rated natural gas as a 0 for renewability.
THE RULING
After thorough research and careful analysis, we feel comfortable in making a prediction as to the potential future of these fuels, as well as their sustainability in the long run. We have concluded that while each of these fuels may have advantages that make them appealing in one form or another, the next couple of decades will show a shift towards cars that operate on biodiesel and electricity. Eventually, we believe that electric cars will become the most commonly used form of transportation, surpassing biofuel cars as the mainstream used in daily driving.
However, we also predict that for many years there will be a combination of fuel sources powering transportation. We feel that it is possible that a typical family might have several differently powered cars for separate purposes. A smaller electric car could be used for the daily commute or to pick up the groceries, while a biodiesel powered SUV might take the family on vacation or perform other long range driving tasks. Differences in these fuels result in niche markets in which they perform well for their given duty.
SUSTAINABILITY: THE FUTURE
We predict that biodiesel will continue to undergo development as an alternative fuel, and will catch on in the next decade or so as a viable option for a versatile fuel based on its good performance and environmental benefits. B80 will probably become a common fueling option, as its power output is close to gasoline, and its price will continue to become increasingly attractive as gasoline costs rise. However, our country will not be able to produce enough biodiesel to establish it as the sole fuel to power our nation. Because of the limit on the amount of biodiesel we can produce, it will not be able to independently replace gasoline as our nation's sole transportation fuel.
Hydrogen powered fuel cells would be a great way to power cars -- if the technology were available. Use of hydrogen will continue to undergo research and development, but it will be at least 10-20 years before fuel cells are commonly sold in cars, and even then the high prices will keep most buyers away. Slow incorporation of hydrogen fueling stations as well as the cost of hydrogen fuel will also be a deterrent to hydrogen-powered cars becoming commonplace. We acknowledge that, in theory, hydrogen fuel cells are a highly efficient method of fueling transportation. Because of this, it is only a matter of time before the technology catches up. However, by the time fuel cells are simple and affordable enough for the daily driver, electric cars will have become everyday vehicles on America's roads, and by then their efficiencies could even be better than that of hydrogen.
Ethanol and methanol are both potential fuels, but limited supplies of source materials and limited power output will not allow these alcohol fuels to be used as a primary consumer fuel. However, they may live on as specialty fuels for buses and other forms of public transportation due to lower demand and the ability of their vehicles to carry more liquid fuel on board.
Electricity will most likely be powering the transportation of the future. In 1996 GM introduced the EV1, a two-seater electric car that could be charged at home in 8 hours and driven for up 150 miles on one charge using the batteries available at the time. While not commercial successes, as only about 1000 cars were built, the EV1s proved that electric cars could be produced and used effectively for daily travel and were a strong competitor to gasoline powered cars. New battery developments will dramatically increase the range of electric vehicles while keeping the efficiency and low cost benefits of the cars intact [20].
Natural gas works well for powering cars today. A few cars have been produced that run on natural gas, as well as a line of city buses. The technology works well, and the emissions are an improvement as compared to gasoline. However, natural gas won't last. It will eventually meet the same untimely end as gasoline, and thus does not provide a sustainable alternative to gasoline-powered vehicles. Natural gas may, however, provide a grace period during the transition away from gasoline.
Finally, we cannot be certain as to what the future will hold for alternative fuels. There are a number of other unpredictable factors including climate change, industrial research and political instability that could play key roles in the great fuel race. However, based on what we know now, we feel that our conclusions represent reasonable conjectures for the future of alternative fuels. One thing is certain, engineers will definitely be at the leading edge of this exciting and important period in history.
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