a) 10 seconds of idling
b) 30 seconds of idling
c) 1 minute of idling
Previous answer:
5. How much land would be needed to replace all of the world’s current use of fossil fuels with biofuels such as wood, charcoal, ethanol, and biodiesel?
b) 4.8 million square miles (equal to the area of the US and India combined)
Vaclav Smil, an energy scientist at the University of Manitoba, explains that renewable energy sources will create energy sprawl because they require more land area to produce than fossil fuels do. All of the oil wells, strip mines, refineries, and pipelines needed to extract fossil fuels worldwide cover an area the size of Belgium, says Smil. That sounds big until you consider the alternative. Electricity-producing solar cells provide about a tenth as much energy per acre as fossil fuel extraction does. Wind farms produce 1/30th to 1/100th the energy per acre. And biofuels like corn ethanol fare even worse: from 1/300th to 1/1000th the energy per acre. Even if you use the entire US corn crop for ethanol, declares Smil, “you would supply 13 percent of [US] gasoline.”
