Any organic chemists out there? It occurred to me that whenever

[hedgehog]

energy is transferred, say from burning coal to make steam to turn a turbine to generate electricity, some of the energy is lost along the way. (2nd Law of Thermodynamics, IIRC).

So, is there an advantage to using corn to make ethanol fuel to run a car vs. merely burning corn to generate electricity to run a car?

[LynneSin]

1. From what I've read, corn is very inefficient when it comes to making Ethanol

But I am not an organic chemist - just had a year of it in college.

[Whoa_Nelly]

2. Ethanol is a dirty business...and fuel

http://cei.org/op-eds-and-articles/ethanols-dirty-little-secrets

<snip>

But on the question of hydrocarbons, ethanol appears to make things worse.

Alcohol's hydrogen bonds are weaker than those of water or even gasoline, making alcohol more likely to evaporate, both under high heat, and under normal temperatures. In scientific terms, this means ethanol and other alcohols have greater "volatility" than gasoline.

More volatile fuels send more hydrocarbons into the air, because less of the hydrocarbons will be burnt up in combustion, and more will simply evaporate and float into the air. Adding 10 percent of ethanol to a fuel mixture increases the volatility, sending more smog-causing hydrocarbons into the air.

<snip>

The ethanol subsidies may harm the ground as well as the air. Subsidizing ethanol in myriad ways creates incentives for farmers to plant far more corn than can be consumed by humans and cattle. This encourages farmers to rely solely on one crop -- corn, because the government is propping up its demand and supporting its price.

More at link

[the redcoat]

3. This idea has been considered

and it is basically consensus in the scientific community that (and research has supported this) burning corn for electrical energy creates more energy that converting it to ethanol.

And the difference between the two methods is SIGNIFICANT.
From http://www.scientificamerican.com/article.cfm?id=bioelectricity-versus-biofuel :

"The new study shows that burning biomass to produce electricity rather than converting it to ethanol (made from corn kernels or the other parts of the plant, so-called cellulosic ethanol) delivers 81 percent more miles per acre of transportation in electric vehicles than ethanol burned in internal combustion, even taking into account the lifetime costs of the expensive batteries available today. "

[hedgehog]

4. Wow! Turns out my gut analysis was right! Thanks!

[uncle ray]

5. more energy, and more emissions.

over twice as much. which is still pretty clean i think.

i'm not saying it's a bad idea, but the emissions need to be taken into consideration. and burnt corn smells bad, too.

ultimately, long term i think much better sources for ethanol will be utilized than corn.

[the redcoat]

6. Here's another snip from the article

"From the atmosphere's point of view, growing biomass to burn in a power plant and using the electricity to move a car avoids 10 tons of carbon dioxide emissions per acre, or 108 percent more emission offsets than ethanol. "One other aspect of the electricity pathway is that most emissions are concentrated in one location, which provides perhaps an opportunity for more control of the emissions," Campbell notes. "It also perhaps locates emissions in a place where impacts might not be as harmful as where cars are driven today." "


So, I agree with you, it needs to be taken into consideration, but just sheer numbers show that burning biomass for electricity significantly cuts down on CO2 emissions. Also, creating CO2 in only one spot introduces the possibility of carbon capture and storage.

[mike_c]

7. the simple answer is yes, burning corn directly yields more energy...

...than converting it to ethanol. The main issue is one of energy DENSITY, however. While there is more energy in the corn used to make x amount of ethanol than there is in the ethanol itself, the corn is less energy dense, so it requires considerably more volume for storage, it has greater mass so it is more difficult to transport, and so on. Converting corn to ethanol CONCENTRATES the energy density into a more energy dense product (not to be confused with mass density), just like fossil fuels concentrate ancient plant biomass into much more energy dense petroleum derivatives.

There is a cost for such concentration-- that's the energy loss that occurs when corn is fermented to ethanol.

[trotsky]

8. Best answer. n/t

[hedgehog]

9. Very good explanation. The only reason to make ethanol is to

provide a liquid fuel for the cars most of us drive now. Burning corn for electricity for battery powered cars appears to be the better option.

[Greyhound]

10. And to keep the outrageous subsidies for corn going. n/t