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For each billion ethanol-equivalent gallons of fuel produced and combusted in the US, the combined climate-change and health costs are $469 million for gasoline, $472–952 million for corn ethanol depending on biorefinery heat source (natural gas, corn stover, or coal) and technology, but only $123–208 million for cellulosic ethanol ...
Corn ethanol has yet to be proven to be as cost effective as gasoline due to corn ethanol being much more expensive to create compared to gasoline. [6] Corn ethanol has to go through an extensive milling process before it can be used as a fuel source. One major drawback with corn ethanol, is the energy returned on energy invested , meaning the ...
Some compounds have high boiling points as well as being air sensitive. A simple vacuum distillation system as exemplified above can be used, whereby the vacuum is replaced with an inert gas after the distillation is complete. However, this is a less satisfactory system if one desires to collect fractions under a reduced pressure.
The global distillation process can be understood using the same principles that explain distillations used to make liquor or purify chemicals in a laboratory. [6] In these processes, a substance is vaporized at a relatively high temperature, and then the vapor travels to an area of lower temperature where it condenses.
Using corn-based ethanol might be an alternative to using petroleum. However, studies that concluded that corn-based ethanol uses less net energy do not factor in the co-products of production. Current corn-ethanol technologies are much less petroleum intensive than gasoline however have the GHG emission levels similar to gasoline. [77]
In this example, a mixture of 96% ethanol and 4% water boils at 78.2 °C (172.8 °F); the mixture is more volatile than pure ethanol. For this reason, ethanol cannot be completely purified by direct fractional distillation of ethanol–water mixtures. The apparatus is assembled as in the diagram.
The pressure at the top is maintained at 1.2–1.5 atm [2] so that the distillation can be carried out at close to atmospheric pressure, and therefore it is known as the atmospheric distillation column. [3] The vapors from the top of the column are a mixture of hydrocarbon gases and naphtha, at a temperature of 120 °C–130 °C.
Cold starting in cold climates is the primary reason ethanol fuel is blended with any gasoline fraction. In Brazil, ethanol fuel is neat at the pumps, hence flexible-fuel vehicles (FFV) including trucks, tractors, motorbikes and mopeds run on E100. The 85% fraction is commonly sold at pumps worldwide (outside the US), and when specifically ...