There are a lot of airplanes not certified mostly crop-dusters running
100% pure Ethanol. The problem with Ethanol is taht it is corosive. It
will eat up your fuel thank, fuel lines, carburator. Cars made to run
in Ethanol have these parts with modified materials to slow down the
corrosion. On airplanes I was told they manufacture stainless steel
fuel thanks and replace the lines with stainless steel ones. These guys
don't care as the diference in Ethanol cost can be 1/3 of Avgas in
Brazil. So for the amount of flying they do it pays for a new engine
every few months.