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"Morgan" <yrmastr@xxxxxxxxxxx> wrote in message
news:0g_Ce.1979299$Xk.931215@xxxxxxxxxxx
> "Bob Eldred" <nsmontassoc@xxxxxxxxx> wrote in message
> news:_jZCe.850$Fk4.520@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> >
> > "The Phantom" <phantom@xxxxxxx> wrote in message
> > news:ercod1do64rqeedsrhn0ejq6797osj7jh5@xxxxxxxxxx
> > >
> >
>
http://seattletimes.nwsource.com/html/nationworld/2002387520_ethanol18.html
> >
> >
> > In the case of ethanol they claim that it takes 29% more fossil energy
to
> > make ethanol than one gets out of it. I take that to mean that it takes
> 129
> > BTU's input to get 100 BTU's of ethanol output. I don't know
> > if that is an accurate number or not, but taking it at face value, what
if
> > the 129 BTU's came from ethanol or other bio-fuels to net 100 BTU's of
> > ethanol product. Would not the yield be 100/129 X 100% = 77.5%. In
> > otherwords, using their numbers and using green fuels to power the
> process,
> > the yield of ethanol is 77.5%. That sounds pretty damn good to me. I'll
> bet
> > it is as good or better than gasoline from petroleum using the same
> > rational.
>
> You misunderstood the gist of the argument. Making 100 Btu's of ethanol
> fuel value requires an input of 129 Btu. This means that for every 100
> Btu's of ethanol you get, you've already used 129 Btu's of something else.
> If you assume you use ethanol as the fuel for the process, then you keep
> losing ethanol.
>
> The efficiency isn't 77.5% because you've done the math wrong.
>
> Eff = (output - input)/input = (100-129)/129 = -22.5%
>
> Negative efficiency means you are putting more in that you are getting
out.
>
> The 100 Btu's they talk about in the article are NOT net. They are GROSS.
> Therefore you are LOSING 29 Btu's for every 100 Btu's of fuel you made.
Not
> a very good business model - unless you have a subsidy.
I don't by that. I think you are right that is the implication but it makes
little sense. It's basically saying that even with all of the solar input it
still takes more energy to produce than you get out. Why should that be?
Numbers from the USDA that I have seen say that there is about 30,000
BTU/gal net positive from corn ethanol which makes more sense for a "solar
enhanced" product than a net negative. Admittedly those are different than
the numbers in the article no matter how you calculate it. How do you
reconcile their 57% statement about wood?
While I think that the use of food seeds for fuel makes little sense, I
believe that appropriate plants can be used to produce positive energy gain
fuel. Certainly wood did that in the 19th century with no oil or coal. Am I
wrong?
Bob
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