<Nested comments broken. UPDATE: Fixed The Oil Drum Monday Open Thread...>

33 comments on Coal rank and thoughts on EROEI

Comments can no longer be added to this story.

| Show without comments | PDF version

AlanfromBigEasy on February 6, 2006 - 12:08pm Permalink | Subthread | Parent | Comments top
Growing sugar cane is a low energy process (most do not fertilize now in LA). Easy to harvest (masses of 8' tall stalks), low energy to crush.  Sugar mills are usually within a dozen or so miles of the fields (so transportation energy after harvest is trivial). Fermenting sugar cane juice (90% sugar solids) (without purifying for brown then white sugar) is a natural, zero energy input process.

Distallation to useable ethanol is also a relatively low energy process (perhaps 1% or 2% I would guess).  Solar distillation is certainly technically feasible.

Unlike corn ethanol*, sugar ethanol is certainly net energy positive.  Only problem is it can be grown only in Louisiana, Florida and Hawaii inside US and Louisiana is only major producer left.

*If one assigns an energy value to the cattle feed created by corn ethanol byproduct, corn ethanol is also net positive.  One can feed cows is either corn "straight" or extract the ethanol and feed them the mash.  Extracting the ethanol is very much a net positive process.

Comments can no longer be added to this story.
kevinM on February 6, 2006 - 3:13pm Permalink | Subthread | Parent | Comments top
If farmers are growing crops without fertilizing,
then we must assume that over a period of time
their yeilds will fall, since it is not possible
to remove nutrients from soil (by way of removing
crops to another location) and still maintain
fertility.

You say that transportation is minimal, but most
fuel is used along way from sugar plantations.
Although pure ethanol is a good fuel, it still
does not have as good an energy content as oil
or petrol and carting ethanol across the
country does amount carting a certain amount of
'water' [O-H bonds versus C-H bonds] across the
country.

I have not got any figures in front of me, but
the distillation process is not insignificant.
However it might me possible to use dried stalks
to fire the distillation apparatus.

Nevertheless, a large amount of work and capital
investment would be required to produce
relatively small quantities of fuel. There is
no way that the world can produce 84 million
barrels of ethanol a day, or even a quareter of
that quantity, from any sustainable agricultural
system.

All the hype about Brazil running cars on a 15%
ethanol blend is just hype. How many cars are
there in Brazil?  10 million? 20 million? And
in the world? 600 million?  

Biofuels will never be more than a small and
very local contribution to future fuels.  

Comments can no longer be added to this story.
AlanfromBigEasy on February 6, 2006 - 4:15pm Permalink | Subthread | Parent | Comments top
I agree that bio-fuels will be of limited use if the "grand Scheme".

Louisiana persists as sugar cane producer in large part due to the fertility of the soil.  Depletion after two centuries has not been noted AFAIK.  (And let some flood water onto the fields and they will be fertile for millenium.  See Nile Delta).

The bagasse (stalks after pressing) has been used for fuel for small  electrical plants elsewhere (3 to 5 MW from memory from waste from a single sugar mill).

Water and pipeline transportation are both extremely energy efficient.  Blending ethanol with local gasoline and pipelining or barging it out will use little energy.

The limit is not capital or operating expense but land.  Relatively little of Louisiana is suitable for sugar cane production.  Best case, we could supply most of our own needs for liquid fuels with a bit left over for export.

Comments can no longer be added to this story.
Crusty on February 7, 2006 - 8:35pm Permalink | Subthread | Parent | Comments top
All the hype about Brazil running cars on a 15%
ethanol blend is just hype. How many cars are
there in Brazil?  10 million? 20 million? And
in the world? 600 million?  

A 15% ethanol bland simply translates into saying that cars can run completely on ethanol if they were, on average, seven times more efficient. As we know, that is easily achievable. A hybrid like the Toyota Prius is 3 times as efficient as the average American road park. Achieving just a bit over twice that efficiency is actually quite easy. Most electric cars achieve that efficiency already, which is of course the main reason why the auto companies are buying them back and destroying them.

A hybrid usually has something like a 15 to 25 Hp electrical motor for city use, and a 80 to 120 Hp combustion engine for highway use. Considering this, it should be painfully obvious that combining the requirements for a SUV into a hybrid is plain stupid: combining a 25 Hp electrical motor with a 250 Hp engine just because mom likes to make the beast roar when driving the kids to school, borders on insanity.

Just consider this: A car with only 25% of it's current engine power will still get you where you want at each and every legal speed. What good is a family car that can do 150 Mph and drive off-road when you live in down-town New York and your car gets impounded if you are caught doing above 90?

One word: Marketing.

Comments can no longer be added to this story.

33 comments on Coal rank and thoughts on EROEI

Comments can no longer be added to this story.

| Show without comments | PDF version