10.5.1 Butanol versus ethanol

Alcoholic fuels are a perfect replacement for gasoline. Most commonly used is bioethanol with an annual production of 17 335.2 million gallons in 2008 (Renewable Fuels Association, 2009). However, biobutanol offers a number of major advantages over bioethanol (Table 10.7). First and foremost, butanol has a

significantly higher energy content and air-fuel ratio (similar to those of gasoline) and thus an increased mileage. Butanol is well suited to existing car engines without any modifications (ButylFuel, 2009), and it can also be mixed with gasoline in any concentration, while ethanol can only be blended up to 85% with gasoline. Another problem of ethanol is its hygroscopic and corrosive nature, which requires transportation in special tanks and blending shortly before use. Butanol, in contrast, can be blended at the refinery and distributed using the existing infrastructure (pipelines, tanks, pumps, filling stations, etc.). Due to the significantly lower vapor pressure, butanol is safer to handle as well.