The Biofuel Quiz

Hydrogen fuel cells are a feasible alternative to oil, but since they're non-living, they aren't considered biofuels.

Biodiesel blends are indicated by the abbreviation Bxx, where "xx" is the percentage of biodiesel in the mixture. B20 fuel is 20 percent biodiesel and 80 percent standard fuel.

Ethanol is a form of fuel derived from the complex carbohydrates in plants. Potential sources are corn and switchgrass.

Although animal fat can be used as a source of biodiesel, plant oils are the primary source.

In the 1900 World Exhibition in Paris, Rudolf Diesel demonstrated his engine that ran on peanut oil.

A rise in gas prices led President Jimmy Carter to encourage the government to explore alternative fuel sources like algae in 1978.

In just one year, a 100-acre (40-hectare) algae biodiesel plant could potentially produce 10 million gallons (38 million liters) of biodiesel. Experts estimate it would take 140 billion gallons (530 billion liters) of the biodiesel each year to replace petroleum-based products.

Critics of biofuel argue that if food and energy compete for land, food prices may go up. They also fear that since surplus food can be used as a fuel source, food surplus programs for hungry countries could dry up.

Brazil's main source of ethanol is sugarcane, while the United States most commonly uses corn.