Question: Energy from ethanol vs Gasoline
Robert Perrin
To settle a discussion, can anyone provide me with an approxiamate
figure for the difference in energy produced from the burning of one
litre of common grade gasoline and the burning of one litre of
ethanol. Many thanks.
R. Perrin
Uncle Al
Look up the heats of combustion and the densities. More to the
point, petroleum shoots out of the ground in Arabia under high
pressure costing about $(US)1/bbl to produce. The energy inputs
necessary to create a mole of fuel-grade ethanol through
fermentation exceed the heat of combustion/mole. The more fuel
ethanol you make the less energy you have net. Brazil went tits
up on its "ethanol economy," and its inputs were nearly free -
cut down some jungle (er, tropical rain forest) and make money on
the wood, let in squatters to farm sugar cane, screw them at
harvest time.
Also note there is a direct Federal $0.57/gallon subsidy of fuel
ethanol, plus Federal subsidies for growing the corn, Federal
subsidies for irrigation, Federally subsidized crop insurance...
How many times do you want to pay for the same gallon of silage?
All of photosynthesis pivots on a single enzyme called RuBisCO.
RuBisCO is the most abundant protein on the planet - 50% of the
soluble protein in every leaf. It has a turnover rate of
3/second and 1% efficiency - and even that goes to Hell at temps
over 25 C. RuBisCO is the Windoze of enzymes. If there is a god
he/she/it is no fucking good at critical biochemistry. A real
enzyme chugs along at 10^5/sec. DO YOU WANT A GREEN REVOLUTION?
Make RuBisCO a crappy 10% efficient with a crappy turnover arte
of 20/second and every farm boosts output by a factor of 70. We
will be drowning in food.
http://pps99.cryst.bbk.ac.uk/projects/sgirdwood/Index.html
Growing fuel is stooopid.
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
"Quis custodiet ipsos custodes?" The Net!
BAJJERFAN
gasoline (this would mean mostly diesel) are required to produce one liter of
ethanol. This would include all uses such as preparing the ground, planting,
cultivating if this is done, harvesting, drying and transporting the grain, as
well as transporting the ethanol. If you add up all of these sources of fuel
consumption in the production of ethanol you will find that it most likely will
turn out to be an energy loser in that it consumes more fuel than it replaces.
Also the questionable benefits for cleaner air are more than offset by the
pollution of earth and water by the chemicals and excessive use of fertilizer
used in growing the grain.
BAJJERFAN
type in the following search sentence:
heat of combustion of gasoline
on about the 4th page you will find a hyperlink to commbuta your answer
will be contained within
David B Brownell
BTU's per pound, and as I recall, Ethanol produces about 6-7000 BTU's
per pound.
Fuel/air ratio by weight for complete combustion for gasoline--15-1.
For Ethanol, I recall about 7-1.
Dave Brownell
Brian Moore
Uncle Al <Uncl...@hate.spam.net> wrote:
>Robert Perrin wrote:
>>
>> Hello All,
>>
>> To settle a discussion, can anyone provide me with an approxiamate
>> figure for the difference in energy produced from the burning of one
>> litre of common grade gasoline and the burning of one litre of
>> ethanol. Many thanks.
>
>Look up the heats of combustion and the densities. More to the
And Al goes on into one of his typical "aren't I a cute right-wing
nut" rants.
This post should serve as an object example for those on this group
who deify Uncle Al, on the (supposedly) basis of him being a
frequent dispenser of sound chemical information.
Ethanol and other oxygenated fuels will always give you less energy
on a per gram basis; you can think of them as in a sense being a
bit "pre-burned" (i.e. already somewhat oxidized) as compared to
a pure hydrocarbon fuel.
The numbers are about thus:
ethanol, MW 46, 1370 kJ/mol, d = 0.79
gives you about 23 kJ/mL
octane (e.g. iso-octane), MW 114, 5460 kJ/mol, d = 0.69
gives you about 33 kJ/ml
so the octane is about 30% more energy on a volume basis.
As an aside (and a non-political one at that), I used to work for
a company that did refinery construction work and we often did
gasoline blending calculations for various scenarios. Sometimes
the customer would supply a long list of properties that
the fuel had to meet. I remember being surprised that fuel
value was not on the list.
--
Brian G. Moore, School of Science, Penn State Erie--The Behrend College
bg...@psu.edu , (814)-898-6334
Larry Smith
"David B Brownell" <db...@juno.com> wrote in message
news:e1b015c3.01071...@posting.google.com...
Lets assume that 'supply and demand' is in vigor, and that gasoline prices
begin to rise dramatically, approaching the price of 'hooch'.
Can ethanol ever be an attractive substitute fuel?
I really doubt it. When cheap fossil fuels become too expensive to use,
Americans are not likely to resort to agriculture by mule, physical work,
etc.
Faced with such a choice, we would start bailing out of office buildings to
make the pitiful suicides of the Wall Street crash of the 20's look
amateurish.
Maybe electric cars, wind power, and nuclear are on horizon. Physical labor
isn't.
SNUMBER6
>Maybe electric cars, wind power, and nuclear are on horizon.
Do you really think someday science will develop methods to gain energy from
nuclear fission ??? <tongue in cheek>
>Physical labor
>isn't.
Definitely ...
In the Village ....
I am not a number ... I am a free man !!!!
David Bostwick
>>From: "Larry Smith" lar...@online.no
>
>>Physical labor
>>isn't.
>
>Definitely ...
>
Nor is common sense.
Bruce Hamilton
>
>As an aside (and a non-political one at that), I used to work for
>a company that did refinery construction work and we often did
>gasoline blending calculations for various scenarios. Sometimes
>the customer would supply a long list of properties that
>the fuel had to meet. I remember being surprised that fuel
>value was not on the list.
Because it's not a specification property for hydrocarbon fuels to
be used in most gasoline and diesel engines. Given that a refinery
is producing hydrocarbons, the critical parameters are the burning
properties ( octane or cetane numbers ) and the volatility.
For environmental or safety reasons, other properties are also
important. For example, consider the two chemicals used to define
octane ratings in gasoline, they both have similar volatility
properies, and thus have minimal effect on the engine rating tests
used to measure octane.
Heat of
Melting Point Boiling Point Density Vaporisation
C C g/ml MJ/kg
normal heptane -90.7 98.4 0.684 0.365 @ 25C
iso octane -107.45 99.3 0.6919 0.308 @ 25C
When you look at their combustion properties ( converted to gaseous
products ), you'll see the heat of combustions are also similar, but
that the important octane ratings are very different.
Fuel State Heat of Research Motor
Combustion Octane Octane
MJ/kg
n-heptane liquid 44.592 0 0
gas 44.955
i-octane liquid 44.374 100 100
gas 44.682
So there's no point in specifying properties that aren't relevant to
the end use of the product. I concede that some diesels are also sold
as fuel oils and, in those cases, calorific values are specified, as
higher boiling hydrocarbon fuels can have reduced energy due to other
elements or water being entrained in the more viscous and dense fuel.
Bruce Hamilton
Don Wilkins
>,;What would be more interesting is to know how many liters of farm grade
>,;gasoline (this would mean mostly diesel) are required to produce one liter of
>,;ethanol. This would include all uses such as preparing the ground, planting,
>,;cultivating if this is done, harvesting, drying and transporting the grain, as
>,;well as transporting the ethanol. If you add up all of these sources of fuel
>,;consumption in the production of ethanol you will find that it most likely will
>,;turn out to be an energy loser in that it consumes more fuel than it replaces.
>,;Also the questionable benefits for cleaner air are more than offset by the
>,;pollution of earth and water by the chemicals and excessive use of fertilizer
>,;used in growing the grain.
Two items that never enter the calculations.
1. The contribution of the farm belt vote to re-election.
2. Even more important...The loss of topsoil (and corn is a crop which
is a big loser of topsoil).
It is absolutely obscene to raise corn for fuel when there are people
starving on this planet.
David B Brownell
>
> >Maybe electric cars, wind power, and nuclear are on horizon.
>
> Do you really think someday science will develop methods to gain energy from
> nuclear fission ??? <tongue in cheek>
>
You do mean fusion, I assume!?
Dave Brownell
Larry Smith
He was just giving me some well deserved shit. ;-)
I should have mentioned fusion.
I am not a strong fan of nuclear fission power plants, but they have been
around
for decades, gobbling money, making a little electricity, generating waste,
and lining the
pockets of those who managed to dip into the pork barrel during their
construction.
Brian Moore
Bruce Hamilton <B.Ham...@irl.cri.nz> wrote:
>
>Because it's not a specification property for hydrocarbon fuels to
>be used in most gasoline and diesel engines. Given that a refinery
>is producing hydrocarbons, the critical parameters are the burning
>properties ( octane or cetane numbers ) and the volatility.
Thanks for the response. My involvement in gasoline blending calculations
was obviously just a tangential one, and a long time ago at that.
But let me ask you this: if we are looking to just compare automobile
gas mileage and we compare say just a typical gasoline and the same
gasoline blended with a significant fraction of an oxygenated fuel
(like ethanol), my understanding was that oxygenated blends
usually produce a slightly lower m.p.g. Can't at least some of
that effect be attributed to the lesser energy content?
SNUMBER6
>I should have mentioned fusion.
>
>I am not a strong fan of nuclear fission power plants, but they have been
>around
>for decades, gobbling money, making a little electricity, generating waste,
>and lining the
>pockets of those who managed to dip into the pork barrel during their
>construction.
Personally I am an advocate of the Mr. Fusion machines used in the Back to the
Future movies ...
But I am not against fission ... except for France where loss of 60 % or so of
their electicity generating capacity would cause them a lot of hardships ...
I am not against any source of energy that makes sense ... and ignore all
political pressures for or against any of them ...