Can bio fuel ethanol used as a main heating source?
Anything that burns will provide some heat, it will also provide some exhaust.

At today's prices you can save a dollar per gallon by using ethanol over home heating oil.  The problem is that you really shouldn't care about price per gallon, you should care about price per amount of energy released.

Heating oil is about 141 Mega-Joules per gallon.
Ethanol is about 70 Mega-Joules per gallon 100% Ethanol.

At $3.60 / gallon for heating oil, it is a bargain compared to $2.72 for 85% ethanol, because you would need to buy two gallons to equal the amount of theoretical heat available in one gallon of heating oil.  It is even more of a bargain than 95% ethanol (denatured), at $29.31 per gallon.  Note that we won't consider 100% ethanol, as opening the container tends to suck enough humidity from the air to make it 95%.

 $3.60 for ~141 MegaJoules of heating oil (1 gallon) 
 $6.40 for ~141 MegaJoules of 85% ethanol (2.35 gallons)
 $62.15 for ~141 MegaJoules of 95% ethanol (2.12 gallons)


It is not a fuel with a high energy capacity, so you'll need a lot of it.  Cheap sources are not very pure, and are poisoned (to prevent sales on the alcohol market) that means that "burns cleanly" isn't going to apply unless you want even more expensive forms of ethanol.

Some claim that one can recover more heat from burning ethanol as all of the combustive products (including all of the heat) can be captured in the room.  This is highly inadvisable unless you use a double-burn setup, guaranteeing the complete combustion of Ethanol.  Partial oxidation of Ethanol produces acetaldehyde which is quite harmful to lungs and belongings.  Also, most Ethanol is denatured, meaning it has poisons purposefully added to it to prevent consumption (avoiding the alcohol taxes).  The by products of burning the denatured additives are varied and generally unwanted (if not also poisonous).

Partial combustion by-products, like acetaldehyde, are very damaging to certain plastics, making installation costs higher (or hiding those costs in future repair bills).

It makes sense in some places, but in home heating it's not a winning choice unless other factors increase the costs of more mundane solutions.