Fuel *just to harvest*? ie, just combine it?
A good rule of thumb is about 2 gal of diesel per acre for a combine. Larger combines might be able to use less, owing to efficiencies of scale.
On one acre of corn, for irrigated or optimum dryland conditions, you can expect about 150 bushels of corn. Each bushel of corn can produce at least 2.5 gallons of ethanol.
So, rough figures:
Diesel consumption: 2 gal #2/acre, * 100 acres is 200 gallons of diesel.
100 acres times 150 bu/acre is 15,000 bushels, times 2.5 gal/bu, gives 37,500 gallons of ethanol off that 100 acres.
There’s more diesel that goes into getting the corn out of the field, there’s fuel that has to be used to auger the corn into the bin, there’s power or propane that has to be used to dry the corn down to target moisture percentage. Then to get the corn to market, there’s diesel to run the truck, etc. So the fuel balance looks wildly positive if you consider JUST the diesel for the combine. All I’m saying is that there’s more involved.
Oh, for sure — I wasn’t trying to refigure out how much energy goes into making ethanol compared to what comes out. I was just curious as to how much fuel machines of that type and scale go through, in a more general sense. Thanks for the info. :-)
As an aside, gas prices are really bizarre in this area right now. I go back and forth between So. IL and W. KY pretty often, and, for example, in recent years, 87 octane gas in the Carbondale, IL area, is usually about 10 cents higher than around Paducah, KY. The differential may have been slightly higher, since gas topped $3 / gal. (The towns are of comparable size, but Paducah is of course on the Ohio River, and taxes are higher in IL.)
Today, gas in C’Dale was $3.89.9 - $3.99.9, but the stations I saw around Paducah were $3.47.9. You know where I filled up!!!
One last question (I think):
Ok, let’s say the ethanol subsidy (blenders’ credit to the oil companies) is ended. How then would feed grain be processed (ie., would feed itself end up with a different composition than it does now?), and where would the by-products end up? Would there be other useful markets for them?
Someone mentioned methane as a by-product (I’m not sure if they meant as a by-product from processing corn for feed, or as produced by cattle digesting corn or feed!) It would seem that if the former was significant, the methane could be collected. (Maybe.)
Looking at it from another angle, I’m no enviro-whacko, but, methane IS a powerful greenhouse gas.