Crops that double as energy sources are cheap, abundant, and homegrown. Yet as farmers rush to transform food crops into fuel, some environmentalists have begun to fret. Energy & Environment Editor Adam Aston explains:
What are biofuels?
There are two main types: ethanol, made from corn, sugarcane, or other carbohydrate-rich plants; and biodiesel, which is derived from soybeans or other oil-bearing crops, or even from animal fat.
Can I buy ethanol or biodiesel now?
You may already have it in your tank. About half the U.S. gasoline supply is spiked with up to 10% ethanol. U.S. carmakers are promoting a blend called E85, made of 85% ethanol and 15% gas. But to burn this mix vehicle engines must be upgraded, and only about 800 gas stations carry it. Biodiesel is even rarer: 75 million gallons were made last year, versus 4 billion gallons of ethanol.
How "green" are biofuels?
Environmental groups such as the Natural Resources Defense Council like them because, with both E85 and biodiesel, tailpipe pollution and greenhouse gas (GHG) emissions fall. But while air quality may improve, water can suffer. More energy-crop farming may stress already overdrawn water supplies, and increased use of fertilizers could taint surface waters. What's more, as fuel crops rise in value, farmers allot more land to them. In tropical areas such as Indonesia, a boom in biodiesel made from palm oil is encouraging the slash-and-burn clearance of rain forests to create cropland.
Don't you have to consume a lot of energy to make biofuels?
Not really. Thanks to more efficient growing and production processes, the "energy balance" of today's ethanol is positive. For each unit of energy consumed in planting, fertilizing, harvesting, and distilling, ethanol yields about 1.5 units. At 3.0, biodiesel's energy balance is even better. But the Holy Grail is so-called cellulosic ethanol made from woody crops and plant waste. It has an energy balance of up to 36.
Do food supplies suffer if more crops are used to make energy?
So far, the answer is no. Last year, 14% of the corn harvest was used to make ethanol, almost all of it industrial-corn varieties not normally used in food. In some states, though, ethanol plants can process more corn than local farmers can now grow. Worldwide ethanol demand has pushed up the cost of corn by 25% and sugar by 100%. Rising food prices especially hurt the world's poorest nations, many of which depend on U.S. exports.