Verified answer

Ethanol is produced from corn in the USA. Corn is a food plant. By removing some corn harvest from the food market, corn prices jumped. To replace the lost corn, other countries had to cut down tropical rain forests to grow crops. The lost forest reduces the amount of carbon dioxide absorbed from the atmosphere, worsening global warming. In sum, it is a bad idea to convert corn into ethanol. However, the idea of biofuel is fundamentally a good one, if we can convert inedible plant material, such as plant stems, leaves, wood chips etc., into fuel.

> Why can’t/doesn’t the US move to all ethanol-based fuels

So far it's cheaper to burn petroleum-based fuels.

> How is biodiesel produced

There are several different biodiesels, some made from vegetable oils and some from "single celled algae." So far, large scale production has been impractical.

> Vehicles in Brazil use ethanol for fuel

That's a nice tropical country. They can grow sugar cane there. It doesn't grow as well in the USA. Corn grows in the USA, but processing it for ethanol takes more doing than processing sugar cane would.

> Why can’t/doesn’t the US move to all ethanol-based fuels

Why aren't you using the metric system?

Why aren't you typing with a sensible keyboard instead of QWERTY?

These things don't happen overnight, because of inertia and the cost of converting to the new technology.

E85 is 15% ethanol, the rest octane.

There are a few problems with it:

1- It is less energy-dense than octane, and is not correspondingly cheaper at present, so not many consumers are interested.

2-It is hygroscopic (likes to attract water) so it rusts out engines not specially built to tolerate it.

3- Presently, it takes more CO2 to make it than you save using it- hopefully larger-scale developments will fix this.