Chapter 25. Chapter 25: Biofuels

What is the current controversy of food vs. fuel?

Why You Should Care

A major trade-off associated with biofuels exists when potential food crops are diverted for food production or when former cropland is converted from growing food to plants used for biofuel. The objections to this are largely obvious, a big one being that most of the land suitable for growing food is already in cultivation, so it takes away from food production to use that land for growing fuel. Another objection is that some of the crops used for fuel production are rather energy intensive to grow, so many of the environmental benefits of using biofuels are lost. Other objections are political: In the United States and Brazil, the world’s largest producers of bioethanol from corn and sugarcane, respectively, production is largely driven by government subsidy rather than by market demand. This means that some government directives to increase energy independence and environmentally conscious fuel production are at odds with the interests of agribusiness lobbies. Solutions to this issue are two-fold: 1) Develop plants that require the minimum of energy expenditure for cultivation and processing into fuel and 2) take measures to ensure that governmental policies foster their cultivation and processing.

1.

LIHD stands for:

A.

low-input, high-diversity.

B.

low-impact, high-diversity.

C.

low-input, high-density.

D.

low-impact, high-density.

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2.

One advantage of LIHD crops over traditional monoculture biofuel crops is that:

A.

there is a more extensive infrastructure in place for producing biofuel from LIHD crops.

B.

there is more governmental support aimed at producing biofuel from LIHD crops.

C.

there are far fewer greenhouse gas emissions associated with producing LIHD crops on marginal land.

D.

there is more agreement among experts on the environmental soundness of LIHD biofuels than biofuel from monocultures.

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3.

Which of the following is NOT an advantage of producing biofuel from LIHD plants?

A.

Does not displace food production

B.

More total biofuel output per hectare

C.

Can grow on marginal soil

D.

Is less destructive to natural ecosystems

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4.

The combination of crop and biofuel type that has the highest net energy return (biofuel output minus fossil fuel input) is:

A.

LIHD biodiesel.

B.

corn ethanol.

C.

LIHD ethanol.

D.

soy biodiesel.

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5.

Interpreting Graphs: Why do the bars in the second graph extend down instead of up?

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They point down because they represent how much less CO₂ is emitted by using those fuels over burning the same amount of gasoline. Since the numbers are negative, the bottom of the y axis is not set at zero; rather, the top of the y axis range is set at zero with negative numbers increasing downward.

6.

Interpreting Graphs: Why are the units in the first chart gigajoules (a unit energy) per hectare and not liters of fuel per hectare?

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Because one liter of ethanol does not have the same energy content as one liter of biodiesel. Moreover, the other energy products (mostly the grain left over after fermentation) aren't liquid.

7.

Thought Question: The energy balance graph explains that, although the energy output of conventional crops is high, so is the energy input required. This means that the LIHD biofuels produce more net energy than corn or soy. But, if you look below the x axis, you will find the net energy produced by each category calculated and see that corn produces higher net energy per area than two of the three LIHD biofuels. Explain why this is not an error: In other words, explain why the energy produced from corn is still lower than the LIHD crops.

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By using the legend, you will find that most of the energy produced by raising corn is used for non-fuel applications.

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