Ethanol (ETOH), like biodiesel, is a biologically based fuel. While it can be derived from any feed grain, corn is the most common source of ethanol in the US. In fact, approximately 10% of the USís corn production each year goes into ethanol. Ethanolís main advantage comes from the fact that it can be used in many existing gasoline engines.
While burning ethanol does release CO2, the primary green house gas released by fossil fuels, an equal amount of CO2 is absorbed while growing the grains to produce the ethanol. In other words, burning ethanol has a neutral net effect on atmospheric CO2 levels. Burning fossil fuels, by contrast, extracts carbon from reservoirs that are deep in the ground (and therefore outside of the atmospheric system) and adds them to the system; the influx of carbon traps heat and leads to the greenhouse effect.
Pure ethanol is grain alcohol; therefore, it must be denatured (made unfit for human consumption) before it can be sold commercially as fuel ethanol. This is accomplished by blending it with gasoline, predominately in the mixtures E85 and E10. E85 is 85% ETOH and 15% gasoline, and works only in specially made cars.
E10, the most common form of ethanol fuel, is 10% ETOH and 90% gasoline. All US cars are certified to run on E10. In fact, pure ethanol has an octane rating of 113; adding 10% ethanol to gasoline raises the octane by 2-3 points. Due to its high performance, ethanol is used in many racing leagues. Additionally, ethanol is an oxygenate and aids in fuller combustion of fuel because the ETOH molecule contains 35% oxygen by weight, resulting in fewer emissions. Ethanol production has risen in the US in recent years:
Beyond the environmental benefits of using ethanol, there are potential economic benefits as well. Increased production of ethanol has the potential to increase employment in the US and to increase the value of farmland. Additionally, almost half of US ethanol production plants are owned by farmer cooperatives, leading to greater benefits for individual farmers.
While converting to ethanol as a major fuel source has many benefits, there remain significant hurdles to widespread implementation of ethanol-based fuels. Growing and harvesting the crops requires a significant amount of energy. Most tractors and farm machinery run on fossil fuel sources, so growing ethanol crops contributes to the greenhouse effect. Substantial improvements are being made in converting the crops to ethanol, however, making the process cheaper and less environmentally harmful.
Additionally, existing crop space is not increasing. Allocating a large portion of the US cropland to transportation fuels would result in less food to feed a rising population. Ethanol is ultimately limited by crop space and cannot replace gasoline entirely; it can only supplement it. This fact calls into question any decision to spend money to develop the necessary technology to implement ethanol fuels on a wide scale.