E85 (85% ethanol, 15% gasoline) is considered an alternative fuel under the Energy Policy Act of 1992 (EPAct). It is used to fuel E85-capable flex fuel cars, which are available in a variety of models from U.S. and foreign automakers.
The 15% gasoline content in E85 enables flex fuel cars to operate normally under cold conditions; fueling a cars with pure ethanol (E100) creates problems during cold-weather operation. Ethanol can also be mixed with gasoline in lower-level blends, which provide many benefits but are not considered EPAct alternative fuels.
Chevrolet Silverado E85 Handyman Ethanol at SEMA 2006
Other than lower gas mileage, motorists will see little difference when using E85 versus gasoline. E85 has about 27% less energy per gallon than gasoline. However, E85 is typically priced lower than gasoline, so that cost per mile is comparable
E85 Stations
As of 2008, more than 1,600 U.S. fueling stations offered E85 to the more than 7 million flex fuel cars on U.S. roadways. Stations are more common in the corn belt (Minnesota, Iowa, Illinois) but are spreading throughout the country. In fact, E85 is now offered in more than 40 states
E85 Emissions
Although it is an alternative fuel, E85 emits regulated pollutants, toxic chemicals, and greenhouse gases. These emissions are primarily released by fuel evaporation or combustion. However, these emissions are generally reduced compared to those of gasoline. The following section describes the different types of emissions and compares those of E85 to those of gasolin
Evaporative Emissions
Evaporative emissions from E85 and gasoline cars enter the air through permeation, fuel tank venting, and fuel or vapor leaks.
2009 Flex-Fuel HUMMER H2
Permeation vapors, which are released through fuel-line materials, are more of an issue for regular gasoline than E85, though it does occur with E85. Fuel tank venting, which occurs when fumes escape the tank during refueling, is controlled by onboard refueling vapor recovery devices installed in all cars produced since model year (MY) 2000. Evaporative emissions, which are leaks, are becoming less prevalent since new leak-resistant materials and fittings are constantly improvin
Tailpipe Emissions
Tailpipe emissions are the by-products of fuel burning in a car’s engine and emitted from its exhaust system. Major tailpipe emissions include hydrocarbons, oxides of nitrogen (NOx), carbon monoxide (CO) and carbon dioxide (CO2).
When the program tested for regulated tailpipe emissions, it found that E85 resulted in higher CO emissions and lower NOx emissions. The results for non-methane hydrocarbon (NMHC) emissions were mixed but reduced in a majority of the rounds (including the one statistically significant one). Test results for total hydrocarbons (THC) were mixed to the point where no relationship could be discerned
Speciated Hydrocarbons
The mixed results of THC were clarified when the testing team separated (speciated) the hydrocarbons into groups. The test results for each type were statistically significant. E85 led to an increase in formaldehyde and acetaldehyde but emitted less 1,3-butadiene and benzene than RFG. When the hydrocarbons were weighted according to toxicity, total potency-weighted toxics (PWT) were significantly reduced in cars powered by E85.
When pollutants leading to ozone (CO and NOx) were accounted for and weighted, the ozone-forming potential (OFP) of E85 emissions was greater than that of RFG emissions. This overrides the point that the specific reactivity (SR) of a given amount of non-methane organic gases is less for RFG than for E85.