Re: Energy Cost of Ethanol


cnctut wrote:
cnctut wrote:
cnctut wrote:
cnctut wrote:
cnctut wrote:
Greg Hansen wrote:
cnctut wrote:
Greg Hansen wrote:

Reviving the topic of Habshi's subject line, and hoping to avoid the
topic of the content, what is the energy cost of producing ethanol?
Does anyone have some solid references?


Greg

Do you wish to start at--I just bought one bushel of shelled corn at
the elevator for $2 now let's make some ethanol--or here, plant these
seeds and grow a bushel of corn-- then we'll make some ethanol. ;-))

Tut


Starting with the seeds, of course. Bushels of shelled corn don't
appear out of nowhere.

OK--here's some data estimates in KCALS for one acre of corn
production--
Labor 49000
Machinery 420000
Gas 797000
Nitrogen 940800
Phosphorus 47100
Potassium 63000
Seeds 68000
Irrigation 34000
Incecticides 11000
Herbicides 11000
Drying 120000
Electricity 330000
Transportation 70000

Total Inputs 2,896,800 Kilocalories per acre

For ethonal production corn need not be dried/Iowa farmers don't
irrigate/electric fans unnecessary saving 484,000KCAL---bringing the
total inputs to 2,412,800KCAL per acre of corn.

To be continued

Some may disagree with the 2,412,800 KCAL per acre figure--and they may
be correct. The farmer for example may say--I alternate inoculated
legumes (soy beans) with corn every year. This practice fixes about
100 lbs or more usable nitrogen per acre. Also, fertilizer requirements
are diminished by returning everything back to the soil except the
seed.

To be continued

So now we have the approx energy expended (2,412,800 KCALs) to plant
and harvest one acre of corn with some variance.

How many bushels of corn can be produced on this acre?

Numbers vary--record yield is over 300 bushels per acre--average is
near 150 bushels in 2005--up from 71 in 1970.

One bushel of shelled corn weighs 56 pounds--so one acre produces
150x56=8400lbs of corn--therefore the energy expended to produce one
pound of corn is 2,412,800KCAL/ 8400 or 287KCAL.

To be continued

To be continued

To sum to this point--it takes 287KCAL to produce one pound of corn--or
it can be purchased at the elevator for 200/56=3.57 cents

Now, how many gallons of ethyl alcohol C2H5OH (C2H60) can be made from
one bushel of corn?

Iowa State University (ISU) studies suggests that 2.5 gallons per
bushel could be produced under reasonable conditions. Recent studies
have also suggested that by treating ground corn with ultrasound, 30%
more sugar could be attained by improving the brake up of carb
molecules in the corn. For this example though, let's stick with 2.5
gallons per bushel but remember that 2.74 gallons per bushel would be
the probable limit from corn seeds only.

If one bushel of corn (56lbs) produces 2.5 gallons of ethanol--then
56/2.5= 22.4 lbs of corn will produce one gallon.

Before we start fermentation/distillation our energy/$ cost for the
corn necessary to produce one gallon of ethanol is/are:

22.4 lbs corn x 287KCAL per lb= 6428.8 KCALs (corn planted and
harvested)
or
22.4 lbs corn x 3.57 cent per lb= 79.96 cents (corn purchased at
elevator)

To be continued

Now let's take a look at actual ethanol production process. One method
that has work successfully for years ( perhaps not the best ref energy
costs but should work for our calculations)

Finely grind the corn seeds and heat at 212 F in water for 30 minutes
to form a gelatine (or mash). The starch in the mash is cooled then
malted at 152 F(addition of ground sprouted corn--the sprouted material
contains the enzyme diastase which converts the starch to sugar.) After
the material cools to around 70 F the yeast is added--the holding
vessel is capped and fermentation begins.

Chemically, for glucose.... C6H1206----->Enzyme--->2C2H50H (2C2H60)

In 7-10 days the yeast has coverted the sugars to ethanol and
distillation can begin.

Energy calculations remaining:

Grinding/crushing 20.9 lbs of corn (1.5 lb used for malting)
Heating solution to 212F and holding for 30 minutes
Malting (sprouting 1.5 lb of corn)
Grinding/crushing 1.5 lb of sprouts
Distillation of water and ethanol mixture
Misc--manpower, movement of fluids, etc.

To be continued

Correction:

C6H1206------>Enzyme--->2C2H50H + 2C02

.

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