1300 shots of EverClear, please

by Slartibartfast

That's about what it's going to take to fill up your tank with ethanol.*

There has been much discussion about the price of a gallon of gasoline of late.  Some say that oil companies are simply profiting far too much.  Some say that the government is taking too large a cut on taxes.  Some say that we ought to be replacing gasoline with ethanol to the degree possible, and that American corn can relax our death-grip on Middle Eastern oil.

Consider this an open thread to discuss things related to energy.  Me, I'm going to comment a bit more about these things below the fold, because we're all about providing the extras here at OW.  And because I've been thinking about it, which the gentle reader may consider to be an added bonus, depending on the perceived Rightness of my thought processes.

Oil company profits, if we somehow cut them out completely, are going to amount to (at current prices) less than a quarter per gallon**.  Federal, state and local gas taxes account for more like 60 cents a gallon (depending on locale, including 18.4 cents a gallon excise tax).  We can do a link-fest to provide pointers to the cost breakdown if anyone wants, and if anyone can dig up a link that we can agree provides accurate information.  I've seen numbers that come out to show that 55-60% of the price of a gallon of gasoline is raw materials cost (barrels of crude), 15% is refinery cost, and about 20% is federal, state and local tax.  It's certainly possible that oil companies involved in extraction are profiting twice: once from extraction and sales, and again from providing refinery services.  Again, links to sources of information on this topic will, if suitable, be used to update this post.

Ethanol is another topic.  I trust by now that most people are aware that ethanol from fermentation of corn is a losing proposition.  I've only seen a couple of decent breakdowns of the energy balance, but both of them are pretty clear indications that it takes more energy to produce ethanol from corn than is obtained from ethanol combustion.  There are some counterclaims, but this one in particular has some holes whose exact nature I'll leave as an exercise for the reader.***  In any case, until someone can show me a credible set of calculations that shows a net energy outflow from the conversion of corn to ethanol, and that addresses the nontrivial cost to the environment resulting therefrom, I'm relegating the efforts of the corn lobby to continue pursuing this to the slag-heap.  Engineer-Poet, though, has a fallback plan for the corn:

Conclusion:  Not considering other value-added products, it is energetically more efficient to burn shelled corn for heating fuel and use natural gas for motor fuel than it is to use the corn and gas to make ethanol for motor fuel.

Discussion of ethanol production, the above being true, must turn to "cellulosic ethanol".  Engineer-Poet notes that this, too, is not without its problems, but there are other alternative ways to extract energy from heaps of cellulose:

1.3 billion tons of biomass converted to carbon at 25% efficiency yields 325 million tons (325 teragrams) of carbon.  At 7830 calories/gram, this represents 2.54e18 calories (1.06e19 J, 10.1 quadrillion BTU) of energy.  At an efficiency of 80%, DCFC's could convert this to roughly 8 quads of electricity.  This is an average power of 267 GW.  But what's that compared to motor fuel demand?

US gasoline consumption in 2004 was up to 139 billion gallons; at 126,000 BTU/gallon, this comes to 17.5 quads of raw energy.  But gasoline vehicles are inefficient; at 16% efficiency, only 2.8 quads of this gets to the wheels.  Diesel vehicles are better.  The 60 billion gallons of distillate oil consumed in 2004 contained 8.7 quads at 145,000 BTU/gallon; converted to work at 35% efficiency, it would deliver 3.0 quads to the wheels.  The total of 5.8 quads is about 73% of the energy available from the carbon, allowing a surplus for other uses.

The one liability is that the DCFC cycle cannot use energy from sources other than biomass; if productivity runs low, there's the potential for a crisis.  This is why I still like the thermal zinc process (driven by solar or any other heat source).  Its direct path is not as efficient as the DCFC system (93960 calories of carbon yields 84670 calories of zinc, which produces 52500 calories of electricity - about 56% throughput to the DCFC's 80%) but it produces more net energy (via the carbon monoxide, the output from a mole of carbon includes another 68330 calories of chemical energy), more useful byproducts, and zinc can also be regenerated using electricity from any source.  Zinc also allows nearly complete carbon capture even when the energy is used in mobile applications.

So, what CAN you do with 1.3 billion tons?  The answer, I think, is "enough."

New ideas about how to tap into alternate energy sources are needed.  Again, feel free to comment, and I'm going to try updating the post to reflect useful bits of data, links, etc in comments.

*Literary license: technically, Ever-Clear is only 95% ethanol (5% DHMO), so you probably wouldn't want to actually throw shots of it into your fuel tank.  Because that deadly DHMO part will oxidize the bejesus out of your fuel injectors.

**Probably motivated by talking points originating in the white-supremacist movement, only stripped of racial overtones.

***Spoiler hints:

1. That energy that's allocated to "by-products"; how is that accounted for and recovered?
2. What's the assumed efficiency of the conversion from starch to glucose to ethanol?
3. Where does the energy from "coproduct energy credits" come from?

Comments

[Slartibartfast]

I read somewhere that fruit flies are attracted to ethanol in the decomposing fruit, so that'd not surprise me.

[liberaljaponicus]

Slarti,
Don't know if you are thinking about the Tim F post over at Balloon Juice, but if you aren't, it's still worth sharing. If I were still teaching English to medical students, I would hire him to write some introductions to modern science, as this was absolutely brilliant.

[dutchmarbel]

We might also go for cars that drive at 1.5 liter per 100 kilometer.

Have to wait till 2009 though, and not have a large family (or at least none living in the same house).

[Gromit]

dutchmarbel: We might also go for cars that drive at 1.5 liter per 100 kilometer.

Have to wait till 2009 though, and not have a large family (or at least none living in the same house).

Pretty impressive. That comes out to about 150 mpg.

Word has it the next Prius could top 100 MPG, for those of us who need a four door.

[Slartibartfast]

Pretty cool. But at 1200 lb, and (I'm guessing, here) less than a half-liter engine displacement, I don't think this is as much a breakthrough in engine technology as it is a combination of light weight, low drag and the best fossil-fuel engine type for fuel efficiency. The higher-perfomance version gets something like 90-100 mpg, but its engine displacement is probably around 1 liter or less. If we all scaled down our engine sizes, we'd probably be getting a lot better mileage. I'm also curious what highway speed the given fuel consumption is valid for, or if it's just around town.

[hilzoy]

Slarti: with the current Prius, at least, everyone says it gets higher gas mileage in town, which leads some people to say: hah, it's not so impressive if you ever have to drive highways. But no Prius driver I know has had this experience: it's actually slightly better on highways. I get around 55mpg in summer, 45 in winter; about 2-3mpg more on highways (if I had to guess), and 2-3mpg less in town (all those annoying stops and starts. Though no wasted gas at traffic lights, when the motor just shuts off.)

[Slartibartfast]

I was talking about the car linked by dutchmarbel, hilzoy.

I'd have guessed better mileage on the highway for the Prius. In town, as I understand it, the Prius has features that mitigate inefficiencies caused by start-and-stop traffic. However, the degree to which the wasted energy can be recovered is (duh!)always going to be less than 100%, so you're going to be less efficient around town than on the highway.

Of course, there's the added drag to consider, so your fuel economy on the highway is going to be some function of speed.

But: 2890 lbs is a lot.

[liberaljaponicus]

one word: flywheels

[Slartibartfast]

Actually, I think flywheels would almost have to be stored in pairs, so the angular momentum can cancel.

[lightning]

Flywheels are a non-starter, except for pulsed power and small-scale applications. In the event of failure, all the energy in the flywheel will be released at once. BOOM

In politics, the rule is "follow the money"; in physics, the rule is "follow the energy".