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Re: takes 1.5 gallons gasoline to produce 1 gallon ethanol in modern agr

Subject: Re: takes 1.5 gallons gasoline to produce 1 gallon ethanol in modern agriculture
From: Oz
Date: Mon, 26 Jun 2006 19:25:48 +0100
Newsgroups: sci.agriculture, sci.energy, sci.chem
lucasea@xxxxxxxxxxxxx writes
>
>"Oz" <Oz@xxxxxxxxxxxxxxxxxxxx> wrote in message 

>> The energy differences are small between cellulose and startch, both are
>> carbohydrates.
>
>That's not my point.  The huge difference is that we currently have no way 
>of using the cellulose, and your "US grain production" numbers only count 
>the grain itself (mostly starch), not the rest of the plant (mostly 
>cellulose).  Once we are able to use the cellulose to make ethanol, the 
>calculations change considerably for grain crops.

Of course the most effective way to use cellulose is to burn it.
Even in the UK, with large areas of high yields very close (compared to
most global locations) to power stations and centres of population, its
basically not economic to burn straw without subsidy.

>> Also note that I was using the ENTIRE US GRAINS PRODUCTION, in reality
>> only a small fraction of this amount is viable.
>
>The point about cellulosics is that with that technology, you can begin 
>using much larger fractions of the plant.  In grains, the grain itself is a 
>small fraction of the mass of the plant.  Much of the rest is cellulose, 
>currently useless, but should be usable for making ethanol once that 
>technology comes on line.  

1) The grain is not actually a 'small fraction' of the mass of the
plant. Of the above ground production at harvest the grain varies fro,
40-60% of the total production.

2) You haven't properly examined the energy balance I posted earlier.
Bioethanol has substantial losses integral to the fermentation and
distillation costs that make it a bad choice for energy recovery. Much
much much better to grow an oil crop for transport use and use the by-
products for burning.

>Then, you also start to open up other sources of 
>cellulose like trees, since you're not just limited to grains.  Grain is 
>actually probably the worst possible example, precisely because there is so 
>much waste.  

The waste was NOT counted in the energy balance. However you must take
into account fermentation and distillation energy costs.

>Sugar beet is a much better solution with current techology, 

No it isn't.

>and biomass cellulose will probably be far better yet, once it is 
>commercialized.  

Probably not because it would be silly to convert cellulose to
bioethanol (with the high energy losses associated with that) when you
can usefully burn it.

>The main impediment to either is the agro lobby that, along 
>with a rather nasty bipartisan case of Congressional recto-cranial 
>inversion, keep Congress from doing anything useful to help the situation.

Bio fuels are economic (now, just) for burning (electricity, heat) and
in the case of oil crops for transport. Bioethanol is a stupid way to
go, its so inefficient compared to the above. Check out the figires I
posted earlier.

>Well, I think Brazil's experience is that ethanol is a very real solution, 
>and an excellent start.

Brazil uses rather small (percentage wise) amounts of ethanol.
Remember too that the molasses used is a by product, the distillation
comes from the bagasse and its all subsidised.

It would be better to burn the lot and make electricity. They can grow
soya very effectively, too.

-- 
Oz
This post is worth absolutely nothing and is probably fallacious.




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