Why anydrous ethanol (máx.1% water) is not directly used as fuel?

Question

Why anydrous ethanol (max.1% water) is not directly used as fuel?

- Is it necessary to modify the engine to make it possible to run on anhydrous ethanol? If so, what characteristics of the engine need to be modified?

- If it's not possible to use anhydrous ethanol (max.1% water) directly as fuel, why is that?

Note: Current ethanol fuel are hydrated. Even E100 (sold in Brazil) is hydrated, 96% ethanol and 4% water.

Answer 1

We can't make enough ethanol to power all our cars with E85 IF they existed AND we used all the corn produced on EARTH.

So why bother with 100%?

Answer 2

Anhydrous ethanol absorbs water easily from the air, so ethanol tends to end up with water in it unless you take extraordinary precautions to keep it dry.

When ethanol is distilled, it forms a constant boiling azeotrope with 4% water (m/m).  Removing the last bit of water is more work and more expensive.

To run only on ethanol, an engine needs adjustments to the timing, fuel-air mixture, and changes to the computer system, dashboard gauges, fuel injectors, and anything that comes in contact with the ethanol.

Ethanol with a little water is corrosive, so figure on a stainless steel fuel tank and Teflon lined fuel hoses.

So the engine has to be engineered from the start to run on ethanol.  Nothing difficult, but enough differences so you can't convert from an unleaded engine to an ethanol engine.

Answer 3

The first few answers are right, but there is a second reason we don't use ethanol for fuel that's too pure. The government doesn't want people to drink it!

The tax on the drinkable ethanol is much higher than the fuel tax. They require the addition of gasoline to make E-85 so people can't drink it.

Answer 4

First, there's not real difference in fuel for ethanol with 4% or 1% water.  Ethanol comes out of the distillation process with 4-5% water, and it requires more energy and cost to get it down to 1% or less, so it's not really practical.  In other words, we aren't adding water to the alcohol to get to 4% water content ... we have to REMOVE water from the natural distillate.

The modifications to the engine are not very expensive, either way ... mostly changing some seals and lines.