At the moment there are seven different alternative energies poised to move in on a piece of the vehicle market. Compressed and liquefied natural gas, biodiesel, propane, hydrogen, ethanol and electricity can all be converted or used to replace gasoline in vehicles.
"There are a lot of things that are competing for the household transport market," said Massachusetts Institute of Technology professor Henry Jacoby.
While the cost and availability of the vehicles can stop in its tracks an energy market from progressing, the availability of refueling stations poses a much larger problem for cars. Christopher Rice, the manager of the Clean Cities program for the Maryland Energy Administration, said the emerging markets increase competition which helps to keep "everyone honest."
If there's a wealth of at least two products, consumers can choose which one works best or them.
"I see my role as decreasing as much utilization of transitional liquid petroleum as possible," he said.
Rice and Jacoby discussed which energy source works for which kinds of vehicles and what the future may hold.
Compressed natural gas
What works: According to the Department of Energy, natural gas vehicles can produce lower levels of carbon emissions than gasoline. Because the tanks are sealed, they do not produce emissions that evaporate into the atmosphere. Jacoby said the carbon emissions saved isn't a reason alone to buy or convert a car to natural gas. The main reason to buy one is because natural gas is cheap, he said. Compressed natural gas currently costs an average of $2.10 per gallon equivalent, and the U.S. has plenty of it.
This year the Maryland Environmental Protection Agency offered the state's first ever initiative to offer up to a $20,000 voucher for CNG vehicles. According to the Department of Energy's alternative energy vehicle buyer guide, there are three dedicated CNG vehicles and two bi-fuel vehicles which run on CNG or gasoline. Honda, General Motors, Chrysler and Chevrolet all produce CNG vehicles.
What doesn't: The process to get compressed natural gas, hydraulic fracturing -- otherwise known as fracking -- poses environmental risks. However, Jacoby said fracking accounts for just one-third of all natural gas produced in the United States.
Storing CNG tanks poses an aesthetic challenge. In buses CNG tanks typically are stored on top of the vehicle, hidden away. It's more difficult to hide a CNG tank with a car. According to the Department of Energy, the driving range with CNG tanks is generally less than with comparable gasoline and diesel tanks because of the size of the tanks. There are just 585 stations across the United States, with just one refueling station in some states. Hawaii, South Dakota, West Virginia and Maine do not have CNG refueling stations yet. There are currently three in Maryland.
Liquefied natural gas
What works: Liquefied natural gas is produced by purifying natural gas and super-cooling it to minus-260 degrees, which turns it into a liquid, according to the Department of Energy. It's stored in a double-walled, vacuum-insulated pressure vessel. LNG has many of the same benefits as CNG. It produces less carbon emissions, according to the Department of Energy, but the carbon emissions are roughly the same as those of compressed natural gas.
According to the Department of Energy, LNG is better for trucks that travel long ranges because the liquid form is more dense than CNG, and more energy can be stored in it. Jacoby said LNG is starting to take off in long-haul trucks.
What doesn't: The problem with LNG is that there aren't many LNG fueling facilities, Jacoby said. There are just 32 LNG refueling stations scattered across the United States, but mostly concentrated in the west.
To keep the LNG cold, there must be a very sophisticated thermostat to control the temperature, John Kimball, the director of business and programs at Helman Machinery Composites, said. The same process to extract natural gas also applies to LNG. Fracking is still used to extract the natural gas, which is then liquefied.
What works: Electric vehicles include all-electric vehicles, plug-in hybrids and hybrid vehicles. An all-electric vehicle uses batteries to store energy, which powers one or more motors, according to the 2013 vehicle buyer guide.
Electric vehicles have gotten the most buzz in the last two years, with virtually every major car manufacturer. As of February 2013, there were more than 5,900 publicly accessible charging locations, with at least one in each of the contiguous United States.
Rice said electric vehicles are being adopted predominately on the light duty, or regular everyday car side. All-electric vehicles get better gas mileage, with the Honda Fit EV getting 132 gas equivalent miles to the gallon in the city, according to the 2013 vehicle buyer guide.
Maryland also offers two tax credits for electric vehicles and plug-in electric vehicles. An income tax credit up to 20 percent of the qualified electric vehicle's cost and a $2,000 credit against the imposed excise tax both are made to motivate buyers. There is also an exemption that allows plug-in electric vehicles to use the HOV lane regardless of the number of occupants.
What doesn't: While electric cars don't produce tailpipe emissions, there are carbon emissions associated with producing the electricity, depending on where a consumer is located, Jacoby said. If an area produces electricity from coal, it's not saving carbon emissions to power a car with electricity, he said.
Electric vehicles are more expensive than their gasoline counterparts. A new all-electric Ford Focus starts at $39,200, according to the 2013 vehicle buyer guide.
What works: The ethanol vehicles on the market currently are able to run on gasoline, E85, or any blend of the two. Ethanol is created using corn and other plant materials. According to the Department of Energy, more than 95 percent of gasoline contains a low-level blend of ethanol in it.
Rice said the state of Maryland has provided grants for ethanol refilling stations. There are 2,354 ethanol stations in the United States, with 13 across the state of Maryland. The starting price can be relatively cheap for a vehicle. Ford offers an ethanol-capable vehicle with the starting price of $16,200.
There are lower greenhouse gas emissions because the carbon dioxide released when ethanol burns is balanced by the carbon dioxide captured when crops are grown, according to the Department of Energy.
What doesn't: A gallon of ethanol contains less energy than a gallon of gasoline, which means a lower fuel economy, according to the Department of Energy. While overall greenhouse gas emissions are lower because of the vehicle, according to the 2013 greenhouse emissions scorecard, the score remains the same for most vehicles whether it's E85 or gasoline pumping through the vehicle.
What works: Propane is what's known as a mature technology, meaning it's been used in transportation for decades, according to the Department of Energy. It's also the most commonly used alternative motor fuel in the world. The fuel is the by-product of mixing crude oil and natural gasses, according to the Department of Energy.
Rice said propane is a big alternative fuel that is poised to take over the market. Currently the state is working on a project with the University of Maryland, College Park, to add a propane refueling station and buy a handful of propane-powered vehicles, he said. The infrastructure tends to be a lot cheaper, and many places already have the ability to refill a propane tank.
"You're not really compressing it, so some people feel more comfortable [using a liquid]," he said.
There are 2,607 propane stations in the United States, with 15 in Maryland.
General Motors and Ford both offer propane vehicles, though neither list a price in the 2013 buying guide.
The switch to propane can result in reductions of greenhouse gas emissions, according to the Department of Energy.
What doesn't: As of March 2013 numbers, the cost for propane was more expensive than the cost of gasoline at $3.77. Gasoline averaged $3.59 for the month of March.
And in 2010, the United States imported 49 percent of the petroleum it consumed, two-thirds of which was used for transportation in the form of gasoline and diesel. According to the Department of Energy, it leaves the United States vulnerable to supply disruptions, because petroleum is used in producing propane.
What works: Biodiesel is produced from a wide range of vegetable oils and animal fats in the form of B100, B20 or B5 depending on how much diesel fuel is in each. For instance, B20 is 20 percent biodiesel and 80 percent diesel fuel. Blends can reduce tailpipe emissions and can reduce the life cycle of emissions of carbon dioxide by more than half, according to the 2013 buying guide.
There are several types of vehicles that can use B20 biodiesel, including Chevrolets, GMCs, Fords and Dodges, though there are certain qualifications to check before filling a tank with B20.
What doesn't: As of March 2013, biodiesel B20 and above costs more than gasoline. B20 was $3.75, compared to gasoline at $3.59, and B100 cost $4.23, not making it the most cost-effective fuel in terms of the return on investment.
The Chevrolet Express 2500/3500 and GMC Savana 2500/3500 starts its pricing at $38,750. There are only 313 biodiesel stations in the United States, with two in Maryland.
What works: Hydrogen, or fuel cell vehicles, are the newest kind of vehicles on the market. They combine hydrogen gas with oxygen from the air to produce electricity. It has the potential to be an emissions-free alternative fuel that can be produced from domestic resources.
What doesn't: It's also not economical yet, Rice said. The cost to produce hydrogen for vehicles is incredibly expensive, according to the Department of Energy. The challenge is to reduce the cost of production in order to reduce the cost of the fuel cells that would be used. The federal government is currently looking into research and development to reduce the cost.
There aren't any cars on the market yet that run solely on fuel cells, according to the 2013 buyer's guide. There are just 10 hydrogen refueling stations in the country, with none in Maryland.