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

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

Step-by-step 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 =(E_(g)-E_(p))/(E_(p)) * 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 = (76330\,Btu-74488\,Btu)/(74488\,Btu)* 100\,\%`

`\%e = 2.473\,\%`

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