Turning CO2 into Ethanol

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Per the article: "The process is cheap, efficient, and scalable, meaning it could soon be used to remove large amounts of CO2 from the atmosphere."

http://www.popularmechanics.com/science/green-tech/a23417/convert-co2-into-ethanol/

I hope it is indeed cheap, efficient, and scalable. Even 2 out of 3 wouldn't be bad. I wonder how long would it take to make a difference? And how much of a difference it would make?

 

[Moonbeam]

Per the article: "The process is cheap, efficient, and scalable, meaning it could soon be used to remove large amounts of CO2 from the atmosphere."

http://www.popularmechanics.com/science/green-tech/a23417/convert-co2-into-ethanol/

I hope it is indeed cheap, efficient, and scalable. Even 2 out of 3 wouldn't be bad. I wonder how long would it take to make a difference? And how much of a difference it would make?

It won't remove CO2 from the atmosphere because the ethanol will be used for fuel. What it will do is decrease the needs for fossil sources of CO2.

 

[DrDoug]

It won't remove CO2 from the atmosphere because the ethanol will be used for fuel. What it will do is decrease the needs for fossil sources of CO2.

Think home distilleries! My kind of temporary carbon sequestration...

 

[sdifox]

This is indeed great news if it pans out.

 

[Zorba]

The article doesn't directly say this, but it did imply it and I am sure it is true. Breaking the CO2 bond would use as much energy as was released when it was created. I.e. if you set one of these up next to a coal fired power plant to convert all of the CO2 back to ethanol, it would require more energy than the coal plant produced (assuming 33% efficient coal plant and 100% efficient conversion from CO2 to Ethanol, it would require 3 coal plants to convert one coal plant's CO2 into ethanol).

So at the end of the day, while this is very cool, to make any measurable dent in atmospheric CO2 concentrations you'd have to have insane amounts of excess clean power.

It could be very useful as a massive battery, along the lines of a pumpback dam. For example, during the day you use excess solar power to create ethanol, then at night you use the ethanol to run a gas turbine plat.

Edit: Looks like they are at 0.67% efficiency, so it would take 4.6 coal plants to power one unit big enough to clean on coal plant. Not saying this isn't really cool with a lot of good uses, but I think it'll be awhile before we can use it to clean the atmosphere.

 

[Paratus]

It already does pan out in small scale proof of concept plants.

The navy is investigating similar technology because they want aircraft carriers to be able to make their own jet fuel. They've got plenty of power to produce fuel from their nuclear reactors.
http://www.smithsonianmag.com/innovation/fuel-seawater-whats-catch-180953623/


When this technology is powered by wind, solar or nuclear it's actually slightly carbon negative due to the ethanol that sits in tanks waiting to be burned.

So next time some yahoo goes off on how we can't fly airplanes or drive cars, (Chunky cough cough), because Al Gore said so realize we have a carbon neutral way to make hydrocarbon fuels.

 

[Paratus]

The article doesn't directly say this, but it did imply it and I am sure it is true. Breaking the CO2 bond would use as much energy as was released when it was created. I.e. if you set one of these up next to a coal fired power plant to convert all of the CO2 back to ethanol, it would require more energy than the coal plant produced (assuming 33% efficient coal plant and 100% efficient conversion from CO2 to Ethanol, it would require 3 coal plants to convert one coal plant's CO2 into ethanol).

So at the end of the day, while this is very cool, to make any measurable dent in atmospheric CO2 concentrations you'd have to have insane amounts of excess clean power.

It could be very useful as a massive battery, along the lines of a pumpback dam. For example, during the day you use excess solar power to create ethanol, then at night you use the ethanol to run a gas turbine plat.

You're realistically looking at purpose built nuclear to ethanol plants or massive solar farms preferably close to the equator.

If I used WolframAlpha correctly:

• Ethanol has 26.4 MJ/Kg
• Assume 1 GW of power (Nuke, Wind, Solar)
• Assume 25% efficiency
• You get about 275,000 gallons per day.

It would take a lot of power but it's at least feasible, depending on the efficiency.

 

[Moonbeam]

The article doesn't directly say this, but it did imply it and I am sure it is true. Breaking the CO2 bond would use as much energy as was released when it was created. I.e. if you set one of these up next to a coal fired power plant to convert all of the CO2 back to ethanol, it would require more energy than the coal plant produced (assuming 33% efficient coal plant and 100% efficient conversion from CO2 to Ethanol, it would require 3 coal plants to convert one coal plant's CO2 into ethanol).

So at the end of the day, while this is very cool, to make any measurable dent in atmospheric CO2 concentrations you'd have to have insane amounts of excess clean power.

It could be very useful as a massive battery, along the lines of a pumpback dam. For example, during the day you use excess solar power to create ethanol, then at night you use the ethanol to run a gas turbine plat.

Edit: Looks like they are at 0.67% efficiency, so it would take 4.6 coal plants to power one unit big enough to clean on coal plant. Not saying this isn't really cool with a lot of good uses, but I think it'll be awhile before we can use it to clean the atmosphere.

Seems the real functionality here is to use excess power when it would otherwise be wasted to create fuel to burn when fossil when power is needed. I took the 67% to mean that 67% of the CO2 dissolved in the water is converted. Further, I assumed that the fact that catalysts are involved is why the process is electrically efficient, ie, the reaction requires 1.2 volts at room temperature.

 

[Lash444]

And another thing, you aren't thinking about the fact that this makes for a pretty good storage medium. Rather than converting the sun's energy into battery banks, if we could remove carbon dioxide and store it as ethanol...

 

[sdifox]

And another thing, you aren't thinking about the fact that this makes for a pretty good storage medium. Rather than converting the sun's energy into battery banks, if we could remove carbon dioxide and store it as ethanol...

great for remote area with decent sun, couple with solar panel and you can have a sustainable power source.

 

[Jaskalas]

I'd love to know the details.

Copper, Carbon, CO2 + "some energy at room temperature" is still a little too vague for me. They said there are some other byproducts but their design limits them. So you'd have to capture air, filter out the CO2, and "process" it with these materials. Does it consume the Copper and Carbon in addition to the CO2?

We'll need to know just how much Copper, Carbon, and Energy it'd take to reduce atmospheric CO2 back down to 350 PPM.
Scaling to the quantities necessary for, what is essentially, terraforming might be a catch to applying it for that purpose.

 

[Paratus]

I'd love to know the details.

Copper, Carbon, CO2 + "some energy at room temperature" is still a little too vague for me. They said there are some other byproducts but their design limits them. So you'd have to capture air, filter out the CO2, and "process" it with these materials. Does it consume the Copper and Carbon in addition to the CO2?

We'll need to know just how much Copper, Carbon, and Energy it'd take to reduce atmospheric CO2 back down to 350 PPM.
Scaling to the quantities necessary for, what is essentially, terraforming might be a catch to applying it for that purpose.

The catalyst of CU and carbon isn't consumed in the reaction, (the definition of catalyst).

The paper says it has a faradaic efficiency of about 63%. If I understand the term correctly it means that if you supply the correct number of electrons 63% of the CO2 ends up in the target ethanol molecules. The rest form other byproducts. This isn't the total energy efficiency however. There are more losses in the system and I can't tell from the paper what they are.

 

[Darwin333]

I guess the real question is how much CO2 per unit of energy does burning gasoline put into the atmosphere versus a unit of energy being produced from a coal fired power plant? If the coal fired power plant is higher then the clean power source would be better used reducing their use. OTOH, if there is extra electricity at any given time this sounds like a great way to use it.

 

[Screech]

This is a cool result, but the difficulties that remain are essentially that
1) you need decently well concentrated CO2 for this to be efficient at all (ie CO2 out of a tank bubbled through solution); you cant just set the electrodes outside in water and the CO2 in the atmosphere will magically lower. This is always the tricky part with reducing atmospheric CO2 -- getting the atmospheric CO2 concentrated in the first place.
2) The current density at -1.2V vs RHE, even with full load of CO2 bubbling through solution, is ~1 to 2 mA/cm^2, which is decent for an electrochemical process (as you max out around 5 mA/cm2 in water due to mass transport limitations), but would be poor for a thermal process (ie fischer trospch). The long story short for the current density is that you would need a LOT of this to make any substantial dent in the amount of CO2 in the atmosphere or....well anywhere, really. Using -1.2V for the reduction process, assuming an overpotential of ~350 mV for water oxidation, and assuming about 1.3V for the thermodynamic value (because I'm too lazy to look it up...) of the equation for ethanol plus O2-> water plus CO2, you end up with something close to 1.3/(1.2+1.3+.35) = 45% efficiency vs a purely efficient thermodynamic process of CO2 to ethanol.

 

[bshole]

It already does pan out in small scale proof of concept plants.

The navy is investigating similar technology because they want aircraft carriers to be able to make their own jet fuel. They've got plenty of power to produce fuel from their nuclear reactors.
http://www.smithsonianmag.com/innovation/fuel-seawater-whats-catch-180953623/

When this technology is powered by wind, solar or nuclear it's actually slightly carbon negative due to the ethanol that sits in tanks waiting to be burned.

So next time some yahoo goes off on how we can't fly airplanes or drive cars, (Chunky cough cough), because Al Gore said so realize we have a carbon neutral way to make hydrocarbon fuels.

Whatever.... we can't change over from corn to switchgrass for ethanol even with the knowledge of the vast improvement it would be. In the end, follow the money. See which politicians are being bought and by whom. That is what determines our climate policy.

 

[sdifox]

Whatever.... we can't change over from corn to swiftgrass for ethanol even with the knowledge of the vast improvement it would be. In the end, follow the money. See which politicians are being bought and by whom. That is what determines our climate policy.

End the farm subsidy and most of it goes away.

 

[interchange]

So, essentially it's scrubbing CO2 and having a product of ethanol. But of course it doesn't break the laws of thermodynamics so it requires more energy than what you get back from burning the ethanol.

But if you use a green fuel to power it, you've made a CO2 recycling plant.

Cool, but just as recycling doesn't solve our trash problem this doesn't solve global warming. Although, I think much of our problem with energy is related to storage rather than to production. Ethanol is portable (yay) but of course burning it puts that CO2 right back in the atmosphere.

 

[Jaskalas]

The catalyst of CU and carbon isn't consumed in the reaction

If only CO2 and energy are lost by this process, that'd make it a remarkable achievement.
I read that the CO2 is contained in water. Perhaps H2O is lost as part of the final product? Does ethanol really only consist of CO2?

 

[Paratus]

If only CO2 and energy are lost by this process, that'd make it a remarkable achievement.
I read that the CO2 is contained in water. Perhaps H2O is lost as part of the final product? Does ethanol really only consist of CO2?

The chemical formula for ethanol is:

C2H6O

It needs hydrogen. So it does consume water as part of th reaction. However combustion of hydrocarbons like gasoline not only release CO2 but water as well. So it can be water neutral as well as carbon neutral.

 

[Jaepheth]

Think home distilleries! My kind of temporary carbon sequestration...

Certainly gives new meaning to the term "solar still"

 

[Jaskalas]

The chemical formula for ethanol is:

C2H6O

It needs hydrogen. So it does consume water as part of th reaction. However combustion of hydrocarbons like gasoline not only release CO2 but water as well. So it can be water neutral as well as carbon neutral.

So while the CO2 is stored as ethanol, water is also part of that.
Fresh water?
See where I'm going with this?

Now I'm curious how much fresh water it'd require to... put this genie back in the bottle, down to 350ppm.
I'd love to see a proposal with full cost and material layout. Both at current PPM, and future PPM.

 

[Paratus]

So while the CO2 is stored as ethanol, water is also part of that.
Fresh water?
See where I'm going with this?

Now I'm curious how much fresh water it'd require to... put this genie back in the bottle, down to 350ppm.
I'd love to see a proposal with full cost and material layout. Both at current PPM, and future PPM.

I do see where you are going but I'm not sure you saw where I was going.

When we burn a hydrocarbon like the octane in gasoline we get the following:

"The combustion of octane follows this reaction: 2 C8H18 + 25 O2 → 16 CO2 + 18 H2O."

Notice the waste products are CO2 and water which both end up in the environment.

Now this new process uses a catalyst and energy to break apart the CO2 and H2O pulled from the environment to recombine them into C2H6O.

We've already dumped the water we need into the environment by burning the fossil fuel in the first place.

You would be correct that depending on where you put the plant you could negatively effect local water supplies. Globally the process would be neutral.

It maybe you would want put your plants near the ocean. Plenty of CO2 there and access to water.

Regardless of where you get the CO2 and H2O from you're going to spend energy collecting and concentrating the CO2 and filtering the water which will be included in calculating the efficiency of the whole system.

 

[Jaskalas]

"Next to the ocean", is desalination cheap enough to apply? I'm always told its expensive.

I'm interested in us using this discovery, I'm just eager to see it developed with a substantial and well-thought out plan.

 

[werepossum]

I guess the real question is how much CO2 per unit of energy does burning gasoline put into the atmosphere versus a unit of energy being produced from a coal fired power plant? If the coal fired power plant is higher then the clean power source would be better used reducing their use. OTOH, if there is extra electricity at any given time this sounds like a great way to use it.

Another point to consider is that coal is extremely environmentally dirty and energy-intensive to mine, refine and ship, and produces copious toxic solid wastes. Even if this is a net energy loss compared to coal, it could still be a win, especially producing energy to drive co-located demand plants. The base plant could be oversized for median demand and the excess electricity used to generate ethanol which then powers demand generators for peak and over-median demand periods.

 

[interchange]

The water consumption piece is definitely pertinent. While it's true that re-consumption of the ethanol will place more H20 back into the environment, it's a sideways point because we then have to collect (and I'm assuming purify) that water again to re-utilize it. It's the same problem with our water supply now. We don't drink it and have it disappear. We pee it back out into our toilets.