Question

In wet mill ethanol plants, a total energy of 74,488 Btu (British thermal units, a common energy unit) is used to produce 1 gallon of ethanol. If ethanol can provide 76,330 Btu per gallon, what is the net energy yield for one gallon of ethanol?

Answer 1

Answer:

The energy yield for one gallon of ethanol is 2.473 %.

Explanation:

The net energy yield ($\% e$), expressed in percentage for one gallon of ethanol is the percentage of the ratio of the difference of the provided energy ($E_{g}$), measured in Btu, and the energy needed to produce the ethanol ($E_{p}$), measured in Btu, divided by the energy needed to produce the ethanol. That is:

$\% e =\frac{E_{g}-E_{p}}{E_{p}} \times 100\,\%$ (1)

If we know that $E_{g} = 76330\,Btu$ and $E_{p} = 74488\,Btu$, then the net energy yield of 1 gallon of ethanol:

$\%e = \frac{76330\,Btu-74488\,Btu}{74488\,Btu}\times 100\,\%$

$\%e = 2.473\,\%$

The energy yield for one gallon of ethanol is 2.473 %.