Biofuels, or fuels made from organic sources, have been promoted as near-term alternatives to oil. The advantages are that biofuels are renewable, and they can already run millions of cars on the road today without investing billions in electric cars, gas storage tanks, or new types of infrastructure.
However, biofuels today still tend to be more expensive and less practical than gasoline, and their availability is limited. And not all biofuels are created equal.
There are two main types of biofuels on the market today: ethanol and biodiesel.
Biodiesel is renewable, nonexplosive, and biodegradable, and it burns more cleanly than petroleum diesel. It is made commercially from vegetable oil treated with lye to make it more viscous, and with other substances to make it last longer in storage. Mostly it is used in blends with petroleum diesel, in mixes such as B5 (5 percent biodiesel to 95 percent petroleum diesel), B10 (10 percent biodiesel), and B20.
Any diesel car can use biodiesel, although the fuel's availability is limited, and it is usually expensive. We have found that 100-percent biodiesel, called B100, typically costs about a dollar per gallon more than regular diesel. A gallon of B20 can operate most diesel engines with no modification. It costs about 15 to 25 cents more than a gallon of petroleum diesel, but it uses 20-percent less petroleum and burns cleaner.
Since it is made from a wide variety of raw materials, automakers say its quality is inconsistent. So most automakers will not honor the warranty of a diesel car using more than 5 percent biodiesel. Ford, however, recently announced it will warranty its new Super-Duty pickup on up to 20-percent biodiesel.
A fuel related to biodiesel is waste vegetable oil, which some drivers collect from restaurants and recycle into fuel for their cars. But the process of collecting and cleaning the fuel for use in a car is very labor intensive, cars require a fairly expensive aftermarket fuel storage system, and automakers say the vegetable oil can be harmful to engines. Some consumers also convert vegetable oil into biodiesel, but this involves toxic chemicals and may not be legal in many residential neighborhoods.
We tested a diesel car running on all three fuels, petroleum diesel, biodiesel, and waste vegetable oil to compare the fuels, and found biodiesel offered a slight improvement overall.
While these fuels help many consumers save fuel, a bigger problem is that without new technology, the fuel could meet less than 1 percent of America's total need for transportation fuel.
That technology, however, may be on the horizon. Researchers and startup companies have shown that they can make biodiesel (and even organically-sourced gasoline) from algae, using less water than biodiesel or ethanol take today. A few prototype algae refineries are starting to come online, but it will take several years before it becomes widely available, if ever.
Ethanol is much more plentiful than biodiesel, but it is not without problems. Chief among them is the ongoing debate about whether the fuel takes more energy to produce than it creates and whether it produces more greenhouse emissions than just using gasoline. Further, there are concerns about creating ethanol from food stock; A boom in ethanol production in 2007 was blamed for driving up food prices.
The federal government has been promoting ethanol for decades. In 2007, Congress ramped up the amount of ethanol mandated to be blended into U.S. gasoline to 36 billion gallons per year by 2020.
Today, most ethanol comes from corn, but to meet that 36-billion-gallon mandate will require producing ethanol from more advanced, renewable feedstocks, such as agricultural and forestry waste and even municipal trash.
Ethanol is primarily used in two forms, E10, which is 10 percent ethanol blended into most U.S. gasoline, and E85, or 85 percent ethanol, which only cars designated as Flexible Fuel Vehicles can use. Ethanol-industry lobbyists are pushing Congress to raise the 10 percent blend to 15 percent to create a market for the increased production mandate.
When we tested E85 in a flex-fuel Chevrolet Tahoe, we found it's fuel economy dropped significantly, and the fuel would end up costing consumers extra at the pump. Furthermore, there is concern that fuel economy credits given to automakers for producing FFVs are causing more gasoline to be burned, rather than less. However, both ethanol and biodiesel produce fewer emissions than their petroleum-based alternatives.
Ultimately, biofuels are about saving oil, not improving the environment or lowering consumers' fuel bills. But with the price of oil expected to rise dramatically in the future, they could provide a valuable alternative in the long run.