We are starting to hear and see quite a bit of buzz about alternative fuels in the news, in commercials, in magazine ads, and in our leaders' speeches, but it's hard to make sense of it all. For any fuel, there are the practical questions like: can you use it in your existing car, can it be used if you modify your existing car, does it require a new car, how much does it cost, and where can you buy the fuel? Then there are the environmental and social questions like: how much does it reduce petroleum dependence, how much benefit is there for solving the climate crisis, what other pollutants does it emit, are there other environmental issues, how does it affect jobs in America, and how does it affect food supply? These are big questions that are not always easily answered.

But, our goal is to break it down so that you can decide whether alternative fuels are for you and if they are, which ones fit your needs the best.

One reason there is so much discussion about alternative fuels is that the United States uses a staggering 3.3 billion barrels of gasoline and 1.5 billion barrels of diesel per year. And use of these fuels is increasing, with transportation being the fastest growing source of US greenhouse gas emissions. Transportation is about 28% of US greenhouse gas emissions. So gasoline and diesel represent a significant and growing greenhouse gas problem.

One of the ways to potentially reduce greenhouse gas emissions is to use alternative fuels, which also have the potential to reduce dependence on foreign oil and vulnerability related to oil imports. There are a number of alternative fuels available that have a range of air quality and greenhouse gas impacts depending on the type of vehicle technology and how the fuel is produced. Read on to find out more about different fuels.

Looking for the short answer?

Looking for the details?

• An alternative for gasoline cars.
• Made by fermenting vegetable matter -- typically corn in the US, but also sugar and grains.
• Can also be made from things like grass, sawdust, and corn husks (cellulosic ethanol) and many companies are working to make this commercially viable.
• Can be used in low levels blends with gasoline in most gasoline engines.
• Can be used in high level blends in flex-fuel gasoline engines.

• GHG benefits relative to gasoline depend on the type of feedstock (see "Lingo" below) like corn or waste wood, the process fuel type (like coal or natural gas heating fuels), the feedstock and finished fuel transport distances, and the blend level.
• Depending on process fuel type and production location, the use of corn based ethanol in an E85 blend can actually increase "well-to-wheel" GHG emissions by up to 40% (assuming a coal based process in the Midwest with 1400 mile train transport to final destination), or it can provide a decrease of up to 20% for locally produced ethanol utilizing natural gas as the process fuel.
• Sugarcane based ethanol produced in Brazil and transported by cargo ship to the US is estimated to reduce GHG emissions by 65% in an E85 blend.
• Locally produced ethanol from cellulosic materials such as forest residue or other plant material is expected to provide reductions of up to 70% for E85 because some of the plant material is used as process fuel instead of coal or natural gas. Many companies are working to develop commercial cellulosic ethanol facilities.

• Land use change (converting prairie land to crop land) can have a significant negative impact on GHG emissions.
• E85 has lower energy content per gallon than gasoline, so 25% more gallons are required than gasoline to travel the same distance.
• At low percentage blends, ethanol can increase smog-causing vehicle emissions, but this can be resolved with controls that limit evaporation of the fuel.
• Corn ethanol has the potential to shift food and grain prices, so technology to increase the yield is important to develop.

• Ethanol is widely available in US as a 5-10% blend with gasoline.
• More limited availability as E85 that can be used in flex-fuel cars.

• An alternative for diesel cars (and trucks and buses).
• Made from vegetable oils or animal fats; used or new oils.
• Chemically different to petroleum diesel with slightly less energy per gallon.
• Can be used as B20 in most diesel cars.
• Pure biodiesel, B100, may require modification in some diesel cars.
• Biodiesel cannot be used in gasoline cars.

• Depending on feedstock and production process, "well-to-wheel" GHGs for B20 range from 10 to 20% lower than conventional petroleum diesel.
• Land use change can have a significant impact on GHG emissions for vegetable oil based renewable diesel. For example, utilizing Indonesian palm oil as a feedstock can result in a doubling of GHG emissions if CO₂ emissions due to rainforest destruction are considered.

• Compared with diesel, "well-to-wheel" emissions of local air pollutants are slightly reduced except for smog-forming NO_x.
• If you switch to a diesel car from a gasoline car because you want to use a biodiesel blend, your emissions of a type of pollution called fine particulate matter will increase. Studies show that fine particulate matter found in diesel exhaust contributes to lung and heart disease.
• The GHG and energy benefits are better for biodiesel from waste oil than from vegetable oil derived from farmed seeds and nuts.

• Supplies of used frying oil, one of the lowest GHG feedstocks, is limited for large scale national adoption of biodiesel... but since it is still a small market, you may be able to find it near you.

• A gaseous fuel compressed into a vehicle tank. It can be a gasoline alternative for passenger cars (like the Honda Civic) or a diesel alternative for buses and shuttles.
• Natural gas is primarily methane. It is usually a fossil fuel (not renewable).
• The feedstock can also be garbage (landfill gas) or manure (biogas).

• Can reduce "well-to-wheel" GHGs by 20 to 30% compared to gasoline depending upon whether the source of the natural gas is domestic or foreign.
• One source of GHG emissions for natural gas based CNG is pipeline methane leaks, since methane has 21 times the warming impact of CO₂.

• Good fuel for air quality because of significantly lower "well-to-wheel" emissions of local air pollutants.
• CNG requires many times more storage volume than gasoline or diesel -- you lose at least half of the trunk space in a CNG passenger car.

• For passenger cars, fueling can be done at home with a garage-based fueling system, or there are some fueling stations open to the public.
• For buses and shuttles, fueling is usually done at the bus terminal or a local station open to a variety of users.

• Usually talked about in conjunction with a fuel cell vehicle, which utilizes very efficient electric drive technology.
• Frequently produced from natural gas through a process called steam reforming or from water electrolysis. It can also be produced from ethanol, coal, or other feedstocks.
• In addition to fuel cells, hydrogen can also be used in either modified gasoline or modified natural gas engines, this is called a hydrogen internal combustion engine.
• Often touted as a good fuel for the future because it can be produced from a variety of feedstocks and through many production processes, making it a very flexible fuel.

• "Well-to-wheel" GHG emissions vary based on production pathway and feedstock. For electrolysis, the emissions depend on the type of fuel used to produce the electricity. The emissions are approximately 25%, 50%, 80%, and 90% lower than gasoline vehicles for hydrogen produced from electrolysis using natural gas based electricity, natural gas steam reforming, coal gasification (with carbon capture and sequestration), and biomass gasification, respectively. So, the benefits of using hydrogen can be very large or somewhat modest depending on how the hydrogen got to your fuel tank.

• Storage volume required is large even in highly compressed form.

• Currently extremely limited availability for both hydrogen fuel and hydrogen cars.

• Electric vehicles have a large battery and highly efficient electric drive technology.
• Vehicles can be all electric vehicles (EVs) or plug-in hybrid electric vehicles (PHEV).

• The "well-to-wheel" GHG emission reductions for EVs relative to gasoline vehicles are estimated at 75% for new natural gas based electricity, 80% for new coal plants with (carbon capture and sequestration), 95% for biomass electricity generation, and 100% for nuclear, wind, and other non-combustion renewables.
• The "well-to-wheel" GHG emission reductions for PHEVs relative to gasoline vehicles range from 50% to 67%. The reductions are more modest because PHEVs drive part of the time on gasoline.

• The main problem has been developing batteries that will take the vehicle a sufficient distance with an acceptable weight and life.
• Recent technology developments and investment indicate promise for EVs and PHEVs.

• EVs and PHEVs that are highway-ready are hard to find. They are not yet sold in mass quantities.
• Small EVs for neighborhood transport are available commercially but are not usually on the lot of your local car dealer. An Internet search for neighborhood electric vehicles or NEVs in your area will identify your local retailers.
• Future full-size EVs and PHEVs will be able to plug into regular wall-plugs, which will make fueling fairly easy. In the developed world, electricity is available in virtually all urban and rural buildings.

• In the CTL process, coal is converted into a liquid fuel with properties similar to diesel.
• CTL fuels can be utilized in existing diesel vehicles at a 30% blend level or at a 100% level in new diesel vehicles.
• CTL is an alternative to diesel, so cannot be used in gasoline vehicles.

• Higher "well-to-wheel" GHG emissions than conventional diesel.
• Even with carbon capture and sequestration, at least a 4% increase in GHGs are estimated.

• More expensive than conventional diesel production, especially with carbon capture and storage, which is not yet widely available.
• Some people favor coal to liquids because the US has abundant coal supplies and use of CTL at a 30% blend level offers a "well-to-wheels" petroleum reduction of approximately 28% when compared with conventional diesel.
• CTL fuels require significant quantities of water in the production process, which is a concern is some regions where coal is readily available but water is scarce.

• Coal is widely available in the US, but CTL with carbon capture and storage is not.
• CTL is currently used in South Africa because of the historical anti-apartheid sanctions on oil imports.

Understanding the Lingo:

Blend :: Some alternative fuels are dispensed as a blend of a conventional fuel and an alternative fuel. The blend is usually written as a letter abbreviation for the fuel (B for biodiesel, E for ethanol) and a number that represents the percentage of the alternative fuel in the blend. So, for ethanol, a low percentage blend of 10% ethanol and 90% gasoline is written as E10. Likewise, E85 is 85% ethanol and 15% gasoline. For biodiesel, the low blend is frequently B20 and pure biodiesel is written B100.

Feedstock :: The initial material from which the vehicle fuel is made. The term feedstock is often used when comparing sources of biodiesel and ethanol. It's an important term because the emissions and energy use vary significantly between different feedstocks. Corn, grass, and agriculture wastes are a few examples of ethanol feedstocks (there are many others too). Waste cooking oil from frying, virgin vegetable palm oil, and animal fats are just a few examples of biodiesel feedstocks.

Flex-fuel :: Cars that can run on gasoline or high blends of ethanol or a combination. Many gasoline cars sold in the US are actually flex-fuel cars. If you live in a location where E85 is available, ask your car dealer which cars are flex-fuel. You do not need a flex-fuel car to use the low-blends of ethanol that are standard at the gasoline pump in many states.

Local air pollutants :: Pollutants that affect the local air quality. These are pollutants other than CO₂ and GHGs, like nitrogen oxides (NO_x) and volatile organic compounds (VOCs) that cause smog, and diesel particulate matter, which is a health hazard.

Well-to-Wheel :: The total emissions counted over the entire process from the point where the fuel feedstock is collected from the well to the point where it is consumed in a vehicle. Of course, for many alternative fuels, there is no oil or gas well involved, so well-to-wheel would actually be more accurately referred to as "source-to-wheel."