Which statement describes the energy balance of ethanol as a fuel?

• A. The energy return is high
• B. It yields more energy than input
• C. The energy return is low
• D. It has an infinite energy supply

Answer: (C)

Evaluating the energy balance of ethanol as a fuel means comparing the energy you get from burning ethanol to the energy you had to invest to grow the crop and process it into fuel. The farming, fertilizer, harvesting, transportation, and the processing and distillation all require energy, often from fossil fuels. Ethanol itself has a lower energy content per liter than gasoline, so even when burned you don’t recover as much energy as you would from a gallon of gasoline. When you tally all inputs against the usable energy in the ethanol produced, the ratio tends to be around break-even to modest gains, not a strong net energy gain. That’s why the energy return is considered low. It’s not an infinite energy source, and it doesn’t consistently yield more energy than input.