Ethanol

photo: Nate Brelsford

Properties

Bioethanol is liquid, clear, colorless, biodegradable, low toxicity

Production

Bioethanol is made when biomass is converted to sugars, which are then fermented into ethanol. The process of hydrolysis seperates most of the water from ethanol, leaving an end product that is generally about 95% ethanol and 5% water.

CO₂ Emissions

Combustion of bioethanol does release CO₂ into the atmosphere.

Fuel Blends

Bioethanol can be blended with conventional gasoline at any ratio, but the most common blend is E10 (10% ethanol, 90% gasoline, sometimes called Gasohol), which can be used in existing gasoline engines without modifications and without affecting vehicle warranty. Higher blends, such as E85, require a Flexible fuel vehicle (FFV).

Infrastructure

Bioethanol can use the existing road transport system for conventional fuels, but the corrosive capacity of bioethanol may prevent it from being able to use the pipeline system—a major drawback.

Compared to Gasoline

As a blended fuel, bioethanol reduces emissions of carbon monoxide a number of other pollutants by as much as 25% or more over conventional gasoline.

Advantages

Bioethanol is already compatible, in low blends, with existing gas engines.

Bioethanol is a high octane fuel with lower emissions.

Disadvantages

Bioethanol can be corrosive to metals such as aluminum.

Bioethanol may require the use of too much arable land (to grow the required crops) and too much energy input during production to justify it. As such, costs—financially, environmentally—are currently prohibitive (see below).

The Future

The future of bioethanol lies directly with precisely what composes the biomass used in the production process. Many researchers believe its future is with cellulosic ethanol using biomass such as corn stover and switchgrass.

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