Saturday, September 30, 2006

Turning Water into Wine

Now I am no biochemist, but I like to act like one on my blog. I have been looking for a way to turn electricity, water and air into ethanol. Ethanol being alcohol this is really like turning water into wine. Well alright, it would be more like turning water into Everclear, but add a little grape juice and close enough.

Why would you want to do such a thing?

1) 3 words: take that Jesus.
2) Imagine the money to be made if you could make such a device small enough to put in a Frat House. As long as you have water and electricity you would never run out of alcohol.
3) It allows excess energy from renewable sources like solar and wind to be converted into an easily storable and energy dense liquid. This could then be used to fuel vehicles or run a generator to turn it back into electricity.

Is it possible?

According to this report by David Bradley, yes. You start by taking electricity and water and generating hydrogen and oxygen through electrolysis. Then you use the carbon dioxide in the air with the hydrogen you produced to create ethanol. I am going to coin a phrase and call this "wind ethanol" as the electricity could come from wind power and to differentiate it from corn or cellulosic ethanol.

Carbon dioxide can also be reduced directly to ethanol when different catalysts and process conditions are employed. Several catalyst systems have been described where relatively high ethanol yields have been demonstrated while methane was the other product. For example, an 82.5 % selectivity of CO2 was described (see Journal of Catalysts, 175, pp. 236-244 (1998)), with the byproducts of carbon monoxide and methane (unknown ratio). In (4d), all of the carbon monoxide is assumed to be eventually fully hydrogenated in a secondary reaction zone.

2 CO2 + 6.35 H2 -> 0.825 C2H6O + 0.35 CH4 + 3.175 H2O (4d)
I am not exactly sure what catalysts you would need or how exactly this would work. This journal article talks of using Rh/SiO2 catalysts to generate ethanol. I believe this is an inorganic reaction. I wonder if you could also get a bacteria to do the same thing organically and whether that might be more efficient or cost effective.

I am also not sure how large this lab/factory/brewery/distillery/black box would need to be. My dream would be to have it small enough to put in a house, like a home brewing kit, so that I could fuel my car from home.

What about the economics?
If H2 at 21.2 kw-hr/lb was made with electricity at 5 cents per kw-hr with an O2 credit of $ 0.0909/lb of H2, and the CO2 was provided at no cost, the raw material price of the ethanol made from CO2 and H2 would be near $ 0.29/lb of ethanol. This cost is equivalent to $1.88 per gallon, which is near the cost of ethanol that is made via fermentation of crops. If improvements could be made to minimize methane formation, the raw material price for the ethanol would drop to near $1.65 per gallon. The hydrogenation facility should be energy self-sufficient by tapping the considerable heat of reaction (near 40 kcal/gm-mole of ethanol produced).
Raw materials are $1.65 a gallon, but it doesn't lay out how much would be needed to make the facility to convert it to ethanol or other costs that would be needed to actually produce it. My guess is that it would be more expensive than the corn/cellulosic ethanol because no one appears to be looking into this, but I don't really know.

Could you generate more ethanol from an acre of solar cells than an acre of switchgrass?
Based strictly upon heating values, 1 gallon of ethanol is equivalent to 0.75 gallon of gasoline. If the overall conversion of electricity to hydrogen to ethanol (using equation 4d) is 7.1 kw-hr per lb of ethanol, then the amount of electricity required to displace a gallon of gasoline (as ethanol via hydrogenation of carbon dioxide) would be 9.45 kw-hr per lb of gasoline, or roughly 59 kw-hr per gallon of gasoline.
58 kWh per gallon of gasoline equivalent is equal to 46kWh of ethanol using the .75 conversion factor. According to this Tesla Slideshow, an acre of solar panels in the desert can collect 380MWh/acre/year. That could be converted to 380MWh/46kWh = 8260 gallons of ethanol.

According to Khosla's slide show, an acre of switchgrass could generate 1500 gallons of ethanol a year. The "wind ethanol" (well really "solar cell ethanol" in this case) can therefore create 5.5 times as much ethanol per acre. That sounds really good but it fails in comparison to using the electricity to power an electric battery car directly which could travel 32 times as far per acre.

Anything else you could do with the electricity?

This report also mentions other interesting things that can be done with electricity/hydrogen. One is to turn glucose and hydrogen into ethanol. That process would yield 42% more ethanol per unit of glucose than standard fermentation techniques. Another would be to create ammonia for fertilizer, like I wrote about in Sustainable Artificial Fertilizer.

Could this process be modified slightly to create jet fuel and therefore have a sustainable way to fuel our aircraft that had no carbon emissions? I believe so, but I am not 100% positive.

What is my next crazy biochemistry question?
Now that this one is solved, I would really like to be able to create glucose from electricity, water and air. That way I could use solar panels to create my food rather than plants. If anyone knows how to do this, please leave a comment.


Rebelfish said...

So I saw this video on Reuters about a "water powered car". I was wondering if you
a) had seen this
b) can figure out the catch

They seem to explicitly say that you put in water and nothing else and the car magically splits the molecule apart to run through what I'm guessing is a fuel cell. I don't buy it, and even Wikipedia notes that it "appears to violate the First Law of Thermodynamics". That really would be a Jesus-worthy feat.

Fat Knowledge said...


I saw it quickly and then completely ignored it as it either the greatest scientific breakthrough in the last million years, or complete BS. Given the lack of an explanation, I will go with the later.

It makes me upset that Reuters would cover this without asking critical questions. I mean, come on, if this really did work it would be amazing that it should be on the cover of every magazine. And if it doesn't then it is a total waste of time and raises false hopes.

I don't know what the catch is, because they don't even bother to explain how it really works.

And just when I think the nonsense level can't get any higher I read this comment on TreeHugger:
The thing ihate about water powered cars and anything like fuel cells that need water is that its replacing one thing thats becoming scarce with another.

Why replace oil with water? Isnt most of the US having heat waves and water drying up ?

So why use water then for fuel?

Not only does this guy think that it works, he is concerned about using water as a fuel source, as it is a scarce resource. Oh, my. :)

Post a Comment

Note: Only a member of this blog may post a comment.