Environmental Engineering Reference
In-Depth Information
Corn (1 Bushel)
Corn is cleaned
Corn is milled
Slurry is liquefied
Yeast is added
Fermentation
Liquid is distilled
Waste to animal feed
Ethanol for fuel
(2.5 gal)
FIGURE 5.6
Flow diagram for production of ethanol from corn.
g
asoline
g
allon
e
quiValent
(gge)
Before beginning our discussion about alternative renewable fuels used for trans-
portation purposes, it is important that the reader has a fundamental understand-
ing of the difference between conventional gasoline and diesel fuel energy output
as compared to non-conventional renewable products. Typically, this comparison
is made utilizing a standard engineering parameter known as the
gasoline gallon
equivalent
(GGE), which is the ratio of the number of British thermal units (Btu)
available in 1 U.S. gallon (1 gal) of gasoline to the number of British thermal units
available in 1 gal of the alternative substance in question. NIST (2012) defined
a gasoline gallon equivalent as 5660 pounds of natural gas. The GGE parameter
allows consumers to compare the energy content of competing fuels against a com-
monly known fuel—gasoline.
Table 5.5
provides GGE and Btu/unit value compari-
sons for various fuels.
