Quiz: What You Don't Know About Biofuel


Photograph by Seth Perlman, AP

You know that liquids squeezed and distilled from plants are powering cars and trucks around the world, but how much do you really know about biofuel?

How is biofuel made?

  • By fermenting the sugar components of starch crops
  • By reacting vegetable oil or animal fat with an alcohol
  • By treating plant oil or animal fat with hydrogen
  • All of the above

Starch crops like corn and sugar cane can be fermented to produce fuel alcohol or ethanol, transesterification of oils with alcohol can produce biodiesel, and hydrogen treating of oils produces a kerosene jet fuel.

Why does blending ethanol into fuel improve the combustion of gasoline?

  • Because it contains oxygen
  • Because it lubricates the engine
  • Because it has the same chemical make-up as gasoline
  • All of the above

The oxygen atoms in ethanol help the fuel burn more completely, reducing harmful carbon monoxide emissions. The environmental benefits of ethanol's oxygenate properties helped spur its use as an alternative fuel.

How does ethanol's energy output compare to that of gasoline?

  • It's one-third as much
  • It's two-thirds as much
  • It's three-quarters as much
  • It's about equal

The energy content of ethanol is just two-thirds that of conventional gasoline. Cars using the most common ethanol blend, E10 (gasoline blended with 10 percent ethanol), need 1.03 gallons of the fuel to travel the distance they could cover with one gallon of gasoline.

What country was the leading producer of biofuel in 2010?

  • Indonesia
  • Brazil
  • The United States
  • China

The United States led world production by far at nearly 13 billion gallons (49 billion liters), followed by Brazil at 7 billion gallons (28 billion liters). Together they accounted for 90 percent of global output.

The European Union has a mandate that renewables will make up what portion of transportation fuel by 2020?

  • 5 percent
  • 10 percent
  • 20 percent
  • 25 percent

The EU's Renewable Energy Directive requires 10 percent renewable energy use and transportation by 2020. But due to concerns about destruction of rain forests for palm oil plantations, the EU is implementing sustainability requirements that will restrict some biofuels.

By 2010, ethanol accounted for 4 percent of U.S. fuel consumption by volume. About how much of the U.S. corn crop was devoted to ethanol?

  • 4 percent
  • 10 percent
  • 25 percent
  • 38 percent

In late 2010, the U.S. Department of Agriculture estimated as much as 38 percent (4.8 billion bushels) of the 12.5 billion-bushel corn crop would go to ethanol production that year.

Which of the following biofuels is NOT considered a drop-in replacement for the petroleum product it is replacing?

  • Biodiesel
  • Hydrotreated renewable jet fuel
  • Ethanol

Although all gasoline engines can handle some ethanol, only “flex fuel” vehicles—protected against corrosion and with a sensor to adjust the engine tuning—can handle high concentrations or a pure form of the fuel alternative.

In the United States, what's the “blend wall” in biofuels?

  • The limit on how much of the corn crop can be devoted to ethanol
  • The restriction on how much ethanol can be mixed into gasoline
  • The cellulosic material that needs to be broken down to make biofuel out of weedy or woody non-foot plant material
  • The division between the soy biodiesel and corn ethanol industries

U.S. regulations long limited blending of ethanol in gasoline to 10 percent. The government in 2011 lifted the blend wall to 15 percent for vehicles manufactured after 2001, but uncertainty over implementation meant E15 was slow coming to market.

How does Brazil's ethanol consumption compare to its gasoline consumption?

  • It's about half
  • It's about equal
  • It's double
  • It's three times as much

Ethanol and gasoline sales were about equal in 2010 in Brazil, which has strong policies to promote fuel alcohol from its native sugar cane. All gasoline must be blended with at least 20 percent ethanol, and pure ethanol is available.

Drivers in Brazil have a choice of running their flex-fuel vehicles on 100 percent ethanol or on a gasoline blend that is 25 percent ethanol. When is pure ethanol the cheaper option?

  • Whenever the price of ethanol is lower than the price of gasoline
  • When the price of ethanol is 70 percent of the gasoline price or less
  • Ethanol is always the cheaper option

Drivers have to take into account not only ethanol's price relative to gasoline, but also the fact that they will get lower fuel mileage using the biofuel. Many rely on online calculators to help determine the best deal.

The U.S. Congress levied a $2-per-gallon excise tax on ethanol to help pay for which war?

  • Civil War
  • World War I
  • Persian Gulf War
  • War in Afghanistan

In 1862 the Union Congress imposed a $2-per-gallon excise tax on ethanol, which was commonly used to fuel lamps at the time. The tax remained in place until 1906.

Which of the following plants is not commonly used in commercial biofuel production today?

  • Corn
  • Palm
  • Sugarcane
  • Switchgrass

Switchgrass is one of the non-food plants seen as a promising future biofuel feedstock if cost-effective technology can be perfected to break down its cellulose into sugar molecules. But corn, soy, sugarcane and palm oil dominate the biofuel scene today.





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