Ethanol is much cleaner burning than petrol, just burn some and see. So it stands to reason it must have much lower exhaust emissions. Ethanol has a higher octane than pump petrol too and so resists pinking and knock much better than petrol. If you build an engine with high static compression you have to choose a fuel that can accommodate it. Then that engine will be more efficient than any petrol engine, simply because it’s higher compression. Then IF it’s of comparable swept volume it should output more energy. The British V6 Essex engine is not a modern engine, it’s V6 OHV push-rod with a single cam far from the bleeding edge of engine design, chosen for that reason that’s the point. You’d think no one could think it was anything but the fuel and the compression it’s under. Petrol could of course be made high enough octane with additives, but that would make it much more expensive.
All modern S.I. engines start with settings remembered in the ECU, settings to start the engine easily. Immediately it fires it continues running with feedback from the sensors. That's why you can just put ethanol in a petrol engine with an ECU and the engine will start it'll tick-over, but not much else. The ECU has 'roms and they contain settings for acceleration and powering uphill, so a re-map or a 'Flash' is essential, the first Analogue ECU's did turn out to be FLEX-fuel. That firmware was suppressed perhaps by the oil companies, naturally they wouldn't want every car to be flex, though distributor equipped cars do advance better, ECU's do accommodate for wear in the moving parts, but they're actually programmed to keep the engine in the most economical and powerful state of tune if the emissions are low enough to pass the agreed deal. Unfortunately some cars using 100% petrol wouldn't pass. What I'd like is that if all cars would be able to use ethanol, petrol or actually any proportion of each so the driver could actually fill up with whatever was handiest, but that's a problem because ethanol and petrol have so different optimal compressions. At the moment the only way to optimise an engine for both ethanol and gasoline is to have some sort of compressor or 'charger fitted.
Most Governments know that burning fossil fuel is a major cause of climate change and they've all got a duty of care, that's why all the petrol for sale nearly everywhere has some ethanol in it, that's also why Briton has finally put some bio-fuel duty rebates in place. And even the US has finally ratified the G8 accords to phase out fossil fuel use. Essentially anyone in the UK can get a duty rebate it just has to be a 100% bio-fuel it CAN BE LIGHT OIL (used in a spark ignition engine) or HEAVY OIL (used in a pressure ignition engine) and you must have been charged some road duty for it. The problem is buying 100% bio-fuel is difficult, the oil companies have no reason them sell them, none of the price would actually be for them. The government isn't advertising it (why would they, it would cost them revenue). The 25,000L/year allowance is designed to be just what a private individual would use for personal use.
Of the many fuels that could be used by a sparking internal combustion engine it's been found that volatile liquid fuels are best for cars, for storage in a fuel tank (gases work the best in the engine, but gas storage for cars can be either heavy, unwieldy or both.) So petrol/Gasoline or ethanol. It's also said by oil company agents or even individuals that are innocently echoing oil company arguments, 'There isn't enough farm land to grow enough crops to make enough ethanol for our current fuel needs'. This is kind of true, but 'so what', my ethanol isn't made of corn it's made of cellulose, nowadays ethanol is rarely made of corn, true most ethanol in e85 sold in America is and historically was made of corn grown by farmers, but that's a purely local situation. American corn is too damp to keep so they made it into ethanol as ethanol will keep until you sell it when corn wouldn't. They don't export it and can't no one wants it, it's much too expensive. American farmers get a subsidy to grow it and American buyers get a subsidy to buy it. Years ago Henry Ford Sr often sold his horseless-carriages to farmers, farmers who where told by the salesman 'you can fuel this carriage with moonshine made from corn. Corn you would have fed your horses. And not every day like a horse, only when you use it'. That was true then, at the start of the 20th century then American farmers often made ethanol from corn. This technically is still true, you can make ethanol from anything, well anything with sugars or complex sugars in it, but now ethanol is made of feedstock like used cellulose packaging, grass, straw, or cellulose waste. The people who make it aren't thick and are very socially aware. Also an ethanol optimised engine is at least 1 ½ times as economical and might even be twice as economical as a petrol engine simply because the higher octane allows a higher compression. The other country that makes a lot of ethanol is Brazil they make it from sugar cane juice they power the whole operation by burning the woody sugar cane stalks in boilers that make electricity so they are really power stations they sell the electricity to the grid and make ethanol so they don't buy oil.