was reading a website called the car-bible, and this came up, while reading on fuels:
Clean exhaust - it depends on your definition of the word "clean".
ch3cho
Something that isn't widely publicised is the difference in emissions between corn-based ethanol, as used in America, and sugar-based ethanol, as used in Brazil. We're all told that ethanol blend fuels produce cleaner exhaust and with sugar-based ethanol, that's absolutely true. Even with corn-based ethanol, the gasses measured at an emissions check are lower (about 25% less CO2), which still looks good. But there is something an ethanol E85 vehicle will produce through the exhaust that might surprise you. The exhaust gas contains acetaldehyde (CH3CHO) and lots of it, especially if the fuel source or combustion process is contaminated with water (like cold-start condensation). Acetaldehyde is a known carcinogen (source, source) and suspected neurotoxin (source), and when exposed to its vapors, you or I would likely develop irritation of the eyes, skin and the respiratory tract. In fact, Acetaldehyde is ranked as one of the most hazardous compounds (worst 10%) to ecosystems and human health. It's obvious why this isn't widely publicised, but then you might ask the question "why don't we see this in the emissions test?". Simple. The emissions test doesn't look for it. You can't detect and measure something you're not looking for.
But wait - it gets better. The corn-based ethanol production process consumes more fossil fuel energy than ethanol's actual calorific value. In other words, to produce a gallon of ethanol to be used in E85, it takes more fossil fuel energy than you could simply get by putting a gallon of refined non-blend petrol in your car. And as you know, regular petrol also gives better economy.
website link: http://www.carbibles.com/fuel_engine_bible_pg2.html