Dimitri Hammond

Last Revised: 8th of May, 2006

Alternative fuels for Vehicles

And Their Environmental Implications


In this day and age, in this society, the topic of global warming and air pollution is ubiquitous. Nearly any person on the street can rattle off a list of contributing factors to the depletion of the ozone layer: power plants, trucks, airplanes, etc. What they may not know, however, is that it is civilian vehicles, gas-powered cars, that are the largest polluter. The U.S. Environmental Protection Agency (EPA) actually contributes the largest source of man-made carcinogens to gasoline. The American Lung Association blames transportation for 55.8 percent of outdoor air pollution and 77.3 percent of total carbon monoxide (CO) production (Ethanol). The discerning statistics go on and on.

As these environmental concerns rise and awareness spreads, the calls for alternative transportation fuels get louder. Many options exist with the most prominent being electricity, BioDiesel, ethanol, natural gas, hydrogen, and propane. Each has its own advantages, disadvantages, and obstacles in implementation. In the following pages reside a closer look at these alternatives and their environmental and economic impacts. This will serve as a starting point for anyone who may just want to be aware and educated, or anyone who wants to make a difference.


To allow a basis for comparison, the primary fuels, gasoline and diesel, must first be looked at. "The U.S. Department of Energy estimates that 82 percent of the carbon monoxide, 43 percent of the reactive organic gases (precursors to ground level ozone) and 57 percent of the nitrogen oxides in U.S cities are emitted from petroleum-based transportation fuels" (Ethanol). It's also estimated that 20 million barrels of oil are consumed, per day. At 42 gallons per barrel, that's 820 million gallons a day! Not only do all of these gallons lead to environmental concerns, but half of that oil comes from out of the country thereby leading to many economic security implications.


So what can be done to serve as an alternative to all of these "petroleum-based transportation fuels?" The first option, electric vehicles (EV), is one of the more commonly-known alternative vehicle power plants. EVs store power in an array of batteries and use them to power an electric motor. There are no tailpipe emissions, but the power to charge the batteries has to come from somewhere. Although the source for that charging could be from hydro-electric, nuclear, wind, or solar power, it's most likely from another fossil fuel such as coal. Although the plant is polluting verses the tailpipe, plant emissions are better to manage as a whole rather than individual vehicles.

Another environmental drawback of EVs are the disposal of their batteries. Batteries are acidic and already harmful to the environment since their acids saturate the surrounding soil in landfills. Large battery arrays produced en masse for EVs will eventually only add to the problem. A non-environmental downside is the limited range of the vehicle and long recharge times.

EV technology is improving by the day with numerous EV vehicles on the road and available to the public. Since recharging can easily be done at home, there is not much of a need for a "recharge station" infrastructure. As a compromise between the limited distance of pure EV vehicles and versatility of gas-powered vehicles, Hybrids are often seen on showroom floors at reasonable prices to the consumer. The only real direct environmental benefit from Hybrids are their increased fuel efficiency. These few extra miles per gallon (mpg) still don't compete, however, with older, smaller, and simpler vehicles from the 60s and 70s, such as the VW Beetles, that get approximately the same gas mileage. Modern vehicles often sacrifice good gas mileage for power and speed with common gas mileage in the 15-20 mpg range.


Diesel fuel is more energy-efficient per gallon then gasoline. This is why ten gallons of diesel fuel will provide more power and take you further than ten gallons of gas. Although it produces less carbon monoxide its emissions contain more soot than gas, hence it is considered the "dirtier" of the two. In an attempt to compensate for this dirtiness, BioDiesel has been introduced. BioDiesel is created from vegetable oils, animal fats, or recycled cooking and restaurant grease. These oils are filtered and put through an esterification process by mixing with an alcohol and a catalyst. The most basic process is so simple that one can even do it at home using directions and recipes found on different web sites (see Addison).

On the environmental side, BioDiesel greatly cuts down on carbon dioxide (CO2) and particulate emissions: 67 percent and 47 percent (respectively) from normal petroleum diesel (BioDiesel). Its combustion may smell like french fries, but is still much cleaner than normal diesel. The only combustion byproduct that it does not decrease is NOx, or nitrous oxide. Pure BioDiesel brings about an average 10% increase in nitrogen released into the atmosphere, which is also a significant contributor to global-warming and smog (BioDiesel).

Pure BioDiesel (B100) requires special modifications on typical diesel engines. However, a blend of 20% BioDiesel and 80% petrol diesel (B20) can run in unmodified diesel engines and is the forerunner in reaching the early adapters of BioDiesel. B20 still has significant environmental benefits including 10-12 percent decrease in hydrocarbons, particulate matter, and carbon monoxide, with only an average of 2% increase in NOx (BioDiesel).

As mass production of BioDiesel becomes cheaper, more distribution terminals are sprouting up all over the country. Folk singer Willie Nelson has been endorsing BioDiesel under the BioWillie brand for a few years, and a new terminal was recently opened close to home in Dallas, Texas, to facilitate the distribution of the fuel all around central Texas (Dallas). Fill stations are slowly adopting BioDiesel blends, but mixing and storage provides challenges, especially since BioDiesel has a very particular storage temperature. However, amid these obstacles, fill stations are still opening, with four already in the Austin, Texas, area, alone (Fueling "Station Locator").

One of the other disadvantages of BioDiesel is that if the demand increases enough, more and more crops will need to become dedicated to BioDiesel. To meet this transportation demand in conjunction with food demands, crop acreage will have to start drastically increasing, taking forests, grasslands, and wildlife with it.

Such is the problem for another alternative fuel, ethanol.


Ethanol is fermented sugar or corn starch. Once it is fermented into an alcohol (called ethanol) it can be burned as a fuel. Rarely seen in its pure form, ethanol is usually blended with gasoline. The highest mix is 85% ethanol (E85) and a gasoline engine would need to be specially designed to be able to burn it. However, in a 10% mix with gasoline (E10), ethanol can be used in normal gasoline engines much like B20 can be run in normal diesel engines. E10 is also the highest ethanol mix that new vehicle warantees will allow. E10 is actually sometimes encouraged by car manufacturers because of its clean-burning and performance characteristics (EERE "Ethanol").

Although ethanol is cleaner, it's only slightly so. E85 has only a 25% reduction in ozone-forming emissions, E10 even less (Alternative Fuels "Ethanol"). But any is better than none, and it also helps the U.S. economy by meeting more of its fuel needs from domestic sources. Production also provides a small amount of pollution so the environmental benefits of E10 start to balance out, with the only real benefit being economic (EERE "Ethanol").

E85 has less trivial environmental benefits, but vehicles must be specially designed to run it. This isn't ideal, especially if the vehicle can only run E85. This is one of the driving forces behind the Flexible Fuel Vehicles (FFV). These are becoming more and more common and can use fuels from E85 to pure gasoline. This is one of the things that has helped Brazil's ethanol society.

Brazil started their Ethanol Program in 1975, using ethanol made from sugar cane. Creating ethanol this way is 30% more efficient than creating it from corn. They quickly became the largest example of commercial biomass use. However, in the late 1990s, ethanol usage came to a near halt due to the decrease of global petroleum process. It wasn't until the introduction of FFVs that their ethanol industry revived and the country is now almost entirely energy independent. Although the sugar cane plants contribute to pollution of the area, they shy in comparison to the decrease in CO2 from burning Ethanol versus gasoline, with the net emissions coming to -9.45 Megatonnes Carbon/Year (Brazillian, 14).

In the U.S., 90% of our ethanol comes from corn. And, as with BioDiesel, crop demands will skyrocket if the energy demands on ethanol reach even a fraction of their potential (based on our current energy trends). Many worry about the implication this has on the vast increase of crop acreage resulting in the compromise of soil integrity, wildlife, ranch land, etc (Alternative Energy; Avery).

There are, however, some optimistics out there: "Although growing enough corn and sugar cane to meet our transportation needs would not be feasible at today's demand levels, experts estimate that after food, seed, industrial, feedstock and export needs are met, there could still be 4 billion bushels of surplus corn a year available for ethanol production. This would yield enough ethanol to replace 650,000 barrels of imported oil a day" (Alternative Energy).

So what of the alternatives that don't rely on a huge crop increase?

Natural Gas

Natural gas is a fossil fuel, but it is much cleaner-burning. It is made mostly of methane and is extracted from underground reserves or from landfills and sewage treatment plants. Natural gas is also the gas that is fed to almost every municipal home in America.

Natural gas is stored in two forms: Compressed Natural Gas (CNG) or Liquefied Natural Gas (LNG). CNG is approximately 30% cheaper than gasoline but also performs at only 25% of the energy efficiency of gasoline (Martin; Alternative Fuels "Ethanol"). The most significant benefit of natural gas, though, is how clean it burns. CO, NOx, and CO2 are reduced by 90%, 60%, and 40% respectively (EERE "CNG"). These are all three primary contributors to smog and greenhouse effects.

The most significant problem with using methane as a fuel is that there is more of a chance that it will spill or leak into the atmosphere. Methane may burn cleanly, but in its original state it is a major contributor to global warming. In fact, methane's warming effect is 58 times more than that of carbon dioxide! The only bright side of this story is that methane has a shorter atmospheric life span. at 11 years, than CO2. Methane is released into the atmosphere through a number of places such as cattle and livestock (140 million metric tonnes a year), extraction of fossil fuels (100 million tonnes), volcanoes & geological sinks (unknown tonneage), landfills (25 million tonnes) and biomass burning (40 million tonnes) (Earth). It is through the extraction of fossil fuels that we collect most of our natural gas. However, forcefully extracting more natural gas to meet future energy demands will end up putting even more methane into circulation. Granted, this is only a problem if vehicles, holding tanks, engines, etc, actually leak some methane before combustion, but since its molecular structure is so small, containing it and preventing leaks is a challenge.

However, CNG is still making strides in the world market. Honda has already started mass producing their Honda Civic GX in California which runs solely on CNG. The car gets over 30 miles per gallon and comes with a device for filling its tank from your home's natural gas connection (2005 Civic). Filling stations for all CNG vehicles are becoming more common with many already around the country. Right here in Austin, Texas, we actually already have a couple of our own (Fueling "Station Locator").

Liquified Natural Gas (LNG) is actually natural gas chilled to -259oF. In this state, the natural gas takes up 1/600 the space of gas form. LNG is also not explosive when kept in liquid form. The only time the natural gas is explosive is when vaporized and mixed with air. LNG also doubles the energy efficiency of CNG while still burning just as clean (LNG Fact Sheet).

LNG, however, is a little trickier to store. To keep in liquid form it is stored under constant pressure. Just as water evaporates, LNG will evaporate and that boil-off must be collected to maintain that constant pressure. Fortunately, that collected boil-off can be used to power the tankers and other infrastructure facilities maintaining the LNG (LNG Fact Sheet). Despite these obstacles, plants are still being built. "As of March 2006, there are five LNG projects proposed to be located in California," as well as in Mexico (Liquefied). There are also already-existing plants in Georgia, Louisiana, Massachusets, Puerto Rico, and Maryland.

Extraction and transportation of LNG still has polluting factors. A recent controversy actually has to do with the plants that convert LNG to CNG. They pull in ocean water to warm the LNG so it evaporates into CNG. However, sucking in water also sucks in marine life, killing them. These conversion plants also typically chlorinate the water to keep the passages from growing algae and clogging. This chlorinated water is then fed back in the ocean, wreaking havoc with the aquatic ecosystem (Riley "LNG plan under fire"). Fortunately, all of these problems can be easily solved without compromising the future of natural gas usage.


Hydrogen is another commonly used gas. This one is also found naturally, extracted from fossil fuels. However, there are also ways of synthesizing it from renewable resources, with newer and more efficient ways still being developed and discovered (EERE "H2").

When hydrogen/CNG are mixed 20/80, emissions are reduced even more than pure CNG, without much efficiency hit. Hydrogen as a gas, by itself, doesn't have much energy content. Only when it is liquefied does it provide almost as much as pure CNG (Hydrogen/Natural).

Perhaps the most exciting use of hydrogen is the hydrogen fuel cell. This technique allows extraction of energy from hydrogen in the form of electricity. When hydrogen reacts with oxygen electrons are released. A hydrogen fuel cell used in a vehicle is actually a collection of numerous smaller cells, each producing about 0.7 volts (enough to power a light bulb). These individual cells react hydrogen with oxygen using a platinum catalyst. Other than electrons, the only other waste is water (Fuel-Advanced).

Internal-combustion, in general, is only 35% efficient. Energy reclamation from fuel cells is 85% efficient. When using that electricity to power the motor to move the vehicle the resulting efficiency is 40-60%, still more than internal-combustion (Fuel-Advanced). Although the idea is over a hundred years old, the technology to harness it properly, efficiently, and at the magnitude needed to power an entire vehicle in a cost-effective manner is still being perfected. The consumer is excluded from the hydrogen club, but not for long. Ford is among the many car manufacturers working hard towards consumer hydrogen fuel cell vehicles (see Fuel-Ford).

The main disadvantage with a "hydrogen economy," as people are starting to coin it, is that hydrogen is like methane: post-reaction emission is clean, but pre-reaction (in its pure gaseous form), it is extremely harmful to the ozone. Hydrogen doesn't have near the immediate warming effects that methane has, but as it's released into the atmosphere, it makes its way into the stratosphere where it oxidizes to form water and cools the stratosphere off, throwing off the ozone chemical balance and increasing ozone hole size. It is estimated that 10-20% of hydrogen will leak into the atmosphere from pipelines, storage facilities, processing plants, power plants, and fuel cells in cars. If the economy does revert to more hydrogen with this estimation holding true, then hydrogen amounts in the atmosphere will triple (Hydrogen's; Kjaer).

This leak risk is one of the largest obstacles in putting together an effective and environmentally-friendly hydrogen infrastructure. Hydrogen has perhaps the smallest molecular structure of all the gases making it even harder to contain than methane. This in conjunction with the no-yet-cost-effectiveness of production is what is making the so-called "hydrogen economy" slow-coming.


The last popular alternative is propane. Propane has already been used for years to supply gas to homes in rural areas and backyard barbecue grilles. The already-present infrastructure for providing this is one of the things contributing to the pheasability and immediate use of propane as an alternative.

Propane, often considered Liguid Petroleum Gas (LPG) is a by-product from two sources: natural gas processing and crude oil refining. Most of the LPG used in the U.S. is produced domestically by separating it from the methane in natural gas. LPG has a higher energy rate than E85 and LNG, second only to B20 (Alternative Fuels "Liquefied"). This combined with the 60-90% emission reduction, the accessibility, the price comparison to gas, and the fact that 85% of it is domestic makes this one of the more prominent alternative fuel sources (EERE "Propane" "Propane Benefits"). Cars must be specially modified, however, but there are websites that provide how-to's for people to do it on their own (see Aftermarket).

Unfortunately, propane still relies on a fossil fuel of some sort. This along with the only-slight mileage decrease (compared to gasoline) are mild disadvantages when compared to some of the others looked at in this paper. However, the point of the objective view of this paper towards the more popular of the alternative vehicle fuels is to inform the reader and allow them to make their own decisions and inferences as to which they prefer and/or will use.

There are many different ways to provide propulsion to a vehicle. It is encouraged to keep looking for new ideas from others, or to challenge your own innovativeness. The Stirling Engine is another example of an alternative form of propulsion stemming from a stroke of simplicity and brilliance (see Stirling).

Be careful and aware, however, on your quest for more information. I have provided many links, all of which I have used to gather the information for this essay. As you may notice, there are multiple links for each topic. Since these topics are so political, most of the sites are propaganda for one view (for) or the other (against), and very rarely both. When researching, be sure to remain objective and aware of what you read.

There is no doubt a need for an alternative form of meeting the demands of our world's energy addictions. Different governments, fortunately, recognize this so they offer a variety of programs and incentives to aid in the use and development of alternative fuels. The U.S., and Texas, both have their own incentives (see Texas).

With all of these strides towards a cleaner human presence on this Earth, it will hopefully be around and able to sustain healthy life for years and generations to come. But it all starts now.

Alternative Fuels ~ Dimitri Hammond

Works Cited

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