# Diesel fuel made with RE from CO2 and H2O



## begreen (Apr 27, 2015)

Wow, this is very interesting. Imagine carbon neutral fuel!
http://www.sciencealert.com/audi-have-successfully-made-diesel-fuel-from-air-and-water


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## Corey (Apr 27, 2015)

Interesting, yes, though sadly doesn't seem like it would be economically feasible anytime soon.



> first step involves harvesting renewable energy ... then use this energy to split water into oxygen and pure hydrogen, ...



That process alone has proven to be costly enough to keep hydrogen out of the mainstream fuel supply.  But wait, there is more...



> ...hydrogen is then mixed with carbon monoxide (CO), which is created from carbon dioxide (CO2) that’s been harvested from the atmosphere...



the energy needed to split CO2 into CO is even higher as the energy in that O bond is very high...this is why CO is such a deadly poison...it binds with oxygen in the blood and doesn't let go for anything.  Lastly...



> ...The two react at high temperatures and under pressure, resulting in the production of the long-chain hydrocarbon compounds...



High temperatures and pressure typically mean one thing...high energy.  Given the energy associated with Step 1 is enough to keep fuel from being economically viable, I don't see adding two more energy intensive steps as helping much.  But who knows...maybe if electricity becomes free...or some crazy cheap / highly effective catalyst is developed.


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## woodgeek (Apr 27, 2015)

How many solar panels does it take to fly an A-380 across the pacific??


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## begreen (Apr 27, 2015)

I think you're missing the point. Yes, it will be expensive at first, but the tech is in its infancy. Yes high heat and pressure are used, but so are they for fossil fuel refinement. Certainly this process is a cleaner and greener alternative. Absent is deep sea driiling, tar sands refinement, etc.. From what I read it is much more carbon neutral than fossil fuels.  At 1 and 1.50 Euros per litre it will at least be competitive and it has higher energy content which should provide a bit better mileage. The fact that they have passed the prototype phase and are ready to increase volume is encouraging. It may be just a first step, but it's in the right direction.


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## BrotherBart (Apr 27, 2015)

Hmmm... Off to buy the domain name "thewaterdrum.com" and start talking about peak water.


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## woodgeek (Apr 27, 2015)

Reading the link, this is all hydrogen derived, and thus old 'syngas' technology, like gas to liquids, coal to liquids etc.  The only new thing is the idea of getting the H2 from RE electrolysis.  Given the current enthusiasm in Germany for the H-economy, it makes sense that they would have a bunch of research projects for things to make from the renewable H. 

IMO, however, as soon as you convert the RE electricity to a chemical fuel, you are now taking the thermodynamic hit burning it in a heat engine.  Why would I take solar electricity, turn it to H2 at 80-90% eff, convert that diesel at 80% eff, and then dump it in a diesel engine running at 20% eff?? 

I'm not a fan of H2 fuel cells, but at least that makes a bit more sense.....because I can turn the H2 back into electricity efficiently (unlike an ICE) and then feed an electric drivetrain, or if I use the H2 for seasonal storage, into grid power for a heat pump.


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## Corey (Apr 27, 2015)

Well, I think I see the basic point:  Diesel fuel is carbon and hydrogen.  We can get the carbon from a theoretically 'bad' gas in the atmosphere and water is 'everywhere'.  With just a few more million in research grants, we might find some magic solution to make it feasible.

Though at some point, it becomes more about the laws of physics rather than technology or economics.  I already mentioned the first electrolysis step of the process isn't economically advantageous enough to allow hydrogen to be used as fuel... let alone considering the other two equally high-energy steps.  If you look at it another way, the Fischer–Tropsch process is basically the last two steps of CO + H > HC + O2...that process is not terribly economically feasible even considering solid carbon / coal as a starting point.

Considering atmospheric CO2 is only 400ppm or 0.04% concentration.  For comparison, argon is ~ 0.935% ...over 23 times more plentiful.  I think my last argon for TIG shielding gas was ~$80 for 240cf cylinder.  Even assuming CO2 costs the same to isolate, back of the envelope scratching shows a cubic foot of CO2 is about 52 grams in total, though that's about 14 grams of usable carbon and 38 grams of 'useless' oxygen.  That $80 gets you a little less than 7.5 lbs of carbon... pretty expensive chunk of coal.

Unfortunately, I think articles like are more common than ever, but are more about free publicity for the company, a source of 'feel good news', and a plea for more research funds than they are about any true technological breakthrough, or technology which will help the 'real world' anytime soon.  But who knows... we can always dream ...and pay for more research.


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## begreen (Apr 27, 2015)

Good insight. I would like to know more about where the CO2 is coming from. If it is sequestered from industry or coal burning plants to be converted to fuel how much more attractive would that be then trying to trap it in salt mines.


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## Ambient (Apr 28, 2015)

begreen said:


> Good insight. I would like to know more about where the CO2 is coming from. If it is sequestered from industry or coal burning plants to be converted to fuel how much more attractive would that be then trying to trap it in salt mines.


Simply sequestering or buying carbon credits just hasn't seemed like a real or long term answer.  This really looks promising, now if they could use the dirty fracking waters also, so that material doesn't need to be pumped back underground.


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## woodgeek (Apr 28, 2015)

Um.  If its recovered fossil Carbon, then the process is not C neutral.  Its a two-pass system, after the diesel is burned, the C is in the atmosphere.

The cheapest source of non-fossil C would be biomass.  Cellulosic biomass (aka 'wood') can be processed to yield charcoal (and energy), and the charcoal burned to yield the very clean CO needed for the process.

This process is thus competing with existing thermo-chemical tech to take biomass (typically called 'garbage'), pyrolyzing it, and turning the pyrolysis oil into syncrude and diesel.  I suppose the OP process could add a lot of energy via the H, and thus require much less biomass input per BTU out.

Several refiners have pilots to use biomass pyrolysis oil as a feedstock into their oil refineries.  The bio-crude has a lot higher H and O content that fossil crude, so it helps with processing unusual crudes, making unusual products, balancing the fractions, etc.


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## Dune (Apr 28, 2015)

Corey said:


> Well, I think I see the basic point:  Diesel fuel is carbon and hydrogen.  We can get the carbon from a theoretically 'bad' gas in the atmosphere and water is 'everywhere'.  With just a few more million in research grants, we might find some magic solution to make it feasible.
> 
> Though at some point, it becomes more about the laws of physics rather than technology or economics.  I already mentioned the first electrolysis step of the process isn't economically advantageous enough to allow hydrogen to be used as fuel... let alone considering the other two equally high-energy steps.  If you look at it another way, the Fischer–Tropsch process is basically the last two steps of CO + H > HC + O2...that process is not terribly economically feasible even considering solid carbon / coal as a starting point.
> 
> ...


Pure Argon is much more expensive to isolate regardless of it's relative abundance. CO2 is dirt cheap in comparison.


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## begreen (Apr 28, 2015)

According to the diagram in the article Audi has a partner Climeworks that is harvesting CO2 from ambient air.


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## Corey (Apr 28, 2015)

Dune said:


> Pure Argon is much more expensive to isolate regardless of it's relative abundance. CO2 is dirt cheap in comparison.



I know argon is expensive and CO2 is cheap in the current market, but we need to be sure to compare apples to apples.  The main source of industrial argon is through liquefaction of air and separating out the oxygen, nitrogen, argon, etc.  The main source of industrial CO2 is recovery from other chemical processes (ie making ammonia, etc. where it is in concentrated form) but NOT separating it from the air.

The original article was about pulling CO2 directly from the air.  Granted, there are some easier pathways to getting CO2 from air than the liquefaction required to get argon.  But we're still talking about an exceptionally small percent abundance, and even worse considering this process is really only interested in the carbon.


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## begreen (Apr 28, 2015)

We can agree it's not entirely carbon neutral, nor is driving a car or truck. Would all agree that it's significantly less carbon intensive than current fossil fuel extraction and refinement processes?


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## woodgeek (Apr 28, 2015)

Yes.  But it is not demonstrated at scale or cost. RE + EVs in comparison are at scale, and are closing on cost.


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## begreen (Apr 28, 2015)

Yes, that remains to be seen. They appear to be ready to leave the prototype phase and build to a much larger scale. I guess we'll see. Without a lot of energy resources of its own I can see Germany being more motivated than other countries, especially with the uncertainty of future supplies from Russia.


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## Dune (Apr 28, 2015)

Corey said:


> I know argon is expensive and CO2 is cheap in the current market, but we need to be sure to compare apples to apples.  The main source of industrial argon is through liquefaction of air and separating out the oxygen, nitrogen, argon, etc.  The main source of industrial CO2 is recovery from other chemical processes (ie making ammonia, etc. where it is in concentrated form) but NOT separating it from the air.
> 
> The original article was about pulling CO2 directly from the air.  Granted, there are some easier pathways to getting CO2 from air than the liquefaction required to get argon.  But we're still talking about an exceptionally small percent abundance, and even worse considering this process is really only interested in the carbon.


Most major producers are looking for uses for excess CO2. Sequestering it underground then pulling it out of the air is stupid. 

Industry will figure that out if the process is truly viable.


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## DickRussell (Apr 28, 2015)

Taking the end products of oxidation of a HC fuel, water and CO2, and synthesizing a HC fuel takes more energy than is released by the oxidation back to end products, due to inefficiencies of the steps in the synthesis process. That's thermodynamics; it's inescapable. The fuel thus created must be seen not so much as a "fuel" but more as a battery for the energy used in the synthesis process, and you get out much less than you put in. If the source used in the overall synthesis process is a renewable such as PV, hydro, or wind, then the process is a useful way to make that energy more portable. If the energy source is coal, then the process certainly makes the energy more portable, but certainly not carbon-neutral.


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## TonyVideo (Apr 29, 2015)

What, companies promoting themselves to garner free publicity! A marketing dream scenario. Tesla has done. Chevy did it with the Volt. Nissan did it with the Leaf. I predict a rise in Audi sales. Talk green and make green.


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## georgepds (Apr 29, 2015)

woodgeek said:


> ..
> 
> IMO, however, as soon as you convert the RE electricity to a chemical fuel, you are now taking the thermodynamic hit burning it in a heat engine.  Why would I take solar electricity, turn it to H2 at 80-90% eff, convert that diesel at 80% eff, and then dump it in a diesel engine running at 20% eff??
> 
> ....


 
Perhaps because you have a high energy density fuel that allows you to power a long range vehicle


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## woodgeek (Apr 29, 2015)

georgepds said:


> Perhaps because you have a high energy density fuel that allows you to power a long range vehicle



I hear you, its just that anticipated near future batteries would suffice for most car/light truck replacements, and for grid energy storage over day times scales.

We can suppose that such 'RE diesel' would be needed for heavy equipment (but not really).  I am sure you could turn RE H2 into aviation fuel, but so little FF fuel is used for aviation, we don't really need to 'get rid of it' to solve AGW IMO...and we could just run it on biomass.

Right now, folks are talking about using H2 for _seasonal_ energy storage (mostly in Germany), where batteries are unlikely to cut it in our lifetimes.  In other words, the sun setting every day is not a problem with (anticipated near future) battery back up, but solar going down for 3 mos of winter when heating energy demand is peaking IS a problem in many regions.  I'm personally skeptical of H2, but don't really have a better solution (other than maybe very long-distance HVDC transmission from a sunnier climate).  But for seasonal stroage you want to run the H2 into a fuel cell to get the electricity back (months later) at good cycle efficiency...you wouldn't make diesel and run a ICE generator with it.


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