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Study reviews pathways for recycling CO2 into fuels using renewable or nuclear energy; concludes co-electrolysis with FT production of fuels could be cost-competitive with diesel or gasoline

Estimate of synthetic fuel cost versus electricity price using (a) constant operation, (b) the same assumptions but with highly intermittent operation (a 20% capacity factor); and operating the electrolyzer at a higher current density with (c) constant operation and (d) highly intermittent operation. Graves et al. Click to enlarge.

In a paper published in the journal Renewable and Sustainable Energy Reviews, researchers from Columbia University and the Risø National Laboratory for Sustainable Energy (Denmark) review the possible technological pathways for recycling CO2 into fuels using renewable or nuclear energy, considering three stages: CO2 capture; H2O and CO2 dissociation, and fuel synthesis.

The new review paper analyzes dissociation methods including thermolysis, thermochemical cycles, electrolysis, and photoelectrolysis of CO2 and/or H2O, and then identifies co-electrolyzing H2O and CO2 in high temperature solid oxide cells to yield syngas, and then producing gasoline or diesel from the syngas in a catalytic reactor (e.g. Fischer–Tropsch) as one of the most promising, feasible routes. It further analyzes this pathway in terms of energy balance and economics.

Based on the energy balance and economics estimates presented for this particular co-electrolysis based cycle, the state-of-the-art technologies at each stage of the cycle can be combined to work together efficiently today with an electricity-to-liquid fuel conversion efficiency of about 70%, and with mass production of the components, economic viability is feasible.

With an electricity price of less than 3 U.S. cents/kWh from a constant power supply (e.g. geothermal, hydroelectric, or nuclear), the synthetic fuel price could be competitive with gasoline at around U.S.D$ 2/gal ($ 0.53/L). If a higher gasoline price of $3/gal ($ 0.78/L) is competitive, the price of electricity driving the synthetic fuel process must be 4–5 U.S. cents/kWh, which is a similar range to recent average wholesale electricity prices in the U.S. Intermittent power sources would significantly increase the capital cost of the electrolyzer.

Intermittent power sources would significantly increase the capital cost of the electrolyzer. With intermittent operation, economical fuel production most likely requires additional technology development on the electrolysis system to reduce the capital cost (via achieving durable high current density operation and/or lower manufacturing cost).

—Graves et. al.

Map of the possible pathways from H2O and CO2 to hydrocarbon fuels. “Fischer–Tropsch” represents any of a variety of catalytic fuel synthesis processes similar to the original Fischer–Tropsch processes. Graves et al. Click to enlarge.

Members of the team earlier this year published a paper in the journal Solid State Ionics on their investigation of the high-temperature co-electrolysis of CO2 and H2O using solid oxide electrolysis cells (SOECs) to produce a syngas for conversion into liquid hydrocarbon fuels. (Earlier post.)

They conclude that several developments could enable competitive fuel production using any inexpensive sustainable power sources, including:

  • Further development of the CO2 air capture process and full-scale demonstration, followed by cost reductions from mass production. In the near term, however, CO2 collected from industrial sources rather than the atmosphere could be used in the non closed- loop version of the synthetic fuel process.

  • Demonstration of durable operation of solid oxide electrolysis cell stacks at high current densities (≥1 A/cm2). Since the existing cells can be efficiently operated at such high current densities at the thermoneutral voltage, operating at this point would be a straightforward way to improve the economics, if performance at this operating point can be maintained over long-term operation.

  • Demonstration of intermittent cell operation, which may require development of specialized power management and heat management schemes.

In the review, Grave et al. examine the status of the enabling technologies for each stage, with special focus on the various thermochemical, electrochemical and photochemical energy conversion technologies that could be used for dissociation of H2O and CO2, the stage with the highest energy consumption. They noted that combining more than one stage into a single unit is possible, but there may be benefits to optimizing each stage separately.

With feasible technology development and mass production of the process components, CO2-recycled hydrocarbon fuels can be produced at the scale needed to replace transportation fuels at a price competitive with more conventional fossil-derived hydrocarbons, especially if oil and CO2 sequestration costs are high. The potentially greater sustainability of CO2-recycled fuels over fossil or biomass derived fuels, as well as independence from the geographic and supply related issues of conventional fuels, could also give CO2-recycled fuels a market advantage.

—Graves et al.


  • Christopher Graves, Sune D. Ebbesen, Mogens Mogensen and Klaus S. Lackner (2011) Sustainable hydrocarbon fuels by recycling CO2 and H2O with renewable or nuclear energy. Renewable and Sustainable Energy Reviews, Volume 15, Issue 1 Pages 1-23 doi: 10.1016/j.rser.2010.07.014


The Goracle


Oh, look!... A "study" funded by Big Government that came up with the results that Big Government wants!

Cigarette smoking studies paid for by Big Tobacco are completely trustworthy as well.

Yea Big Government! Spending into bankruptcy is the enlightened way! Boo - people able to control themselves.



Why not start building demonstration plant(s)?


70% conversion efficiency is not that bad at all (if possible).

Huge desert solar power plants could synthetize the transportation fuels.

Possibly, with time, small-scale household synthetizers could be installed, so one would be fairly energy independent (if one has a large solar array on the roof).


It may not be necessary to deal with HTE systems. Archaebacteria can convert CO2 and electricity to methane, and there are hyperthermophilic strains which live at over 100 C temperatures. If a bio-electrolysis cell can run at a high enough temperature to crack potassium bicarbonate into K2CO3 and CO2 (the 100-120 C range), the CO2-liberation half of an atmospheric carbon capture system could run on the waste heat from the methane generator.

Thomas Pedersen

Take 100 energy units of hydro-carbon fuel, e.g. coal. Then convert that into electricity at, say, 45% efficiency. Then use 10% points of that electricity to capture the CO2, and you have 35 units of electrical energy. Then combine the CO2 with 10 units of electricity and some water and, violá, you have 25 units of hydro-carbon fuel! Heureka! (Then burn said hydro-carbon fuel in an ICE and obtain a whopping 5-6 units of mechanical energy to propel the car)

And don't give me the crap about storing renewable energy - that fairy tale has been debunked in discussions about the 'hydrogen economy' a hundred times over.

But great that they can (maybe) make it 'economical' using excess power they suddenly have from a nuclear power plant they have lying around.

Sorry for the harsh tone, but we don't need more technologies that consume energy, we need ones that produce it. Without too much pollution or GHG emission, please.

If it's about stretching our liquid hydro-carbon fuels, make efficient cars, PHEV's if you can. And if people insist on using coal for liquid fuels, use electrolysis hydrogen with gasification of the coal to balance the carbon/hydrogen ratio for the desired liquid fuels instead of combusting the coal and capture the CO2.

Just because it's possible doesn't make it a good idea!

Stan Peterson

More useless nonsense from the Piled higher & Deeper fool at Columbia, who can turn any genuine Science into day-dreams that support his left wing political unreality. The same gentleman who has destroyed Scientific American magazine.

So you really believe that you can de-oxidize carbon without expending more energy than what the world obtains by oxidizing hydrocarbons in the first place? Of such pablum, are perpetual motion machines constructed. Just where would you obtain more energy than the world now uses, and what would the side effects be?


I think you missed the point Stan. No "perpetual motion machines". Two energy sources. (Just take a look at the second chart).

High temperature co-electrolysis of H2O and CO2 makes very efficient use of electricity and heat (near-100% electricity-to-syngas efficiency)

An endothermic reaction could use waste heat allowing for the "near-100% electricity-to-syngas efficiency".

I understand the idea as a systems approach to obtain higher efficiencies from primary energy sources by extract more useful energy/work in a way similar to the CHP setup. We could call it something like 'Combined Fuel and Power'.

I wont go further into it cause I haven't read the paper, but always wondered about similar things. I like the systems approach.


Stan and Thomas might want to lay off the happy sauce for a while... no one is saying to burn fossil fuels to then take the electricity and capture CO2 and FT it to hydrocarbons that is just silly, use the hydrocarbons and go syngas to FT directly or hydrogenate over catalysts.

This is about using electricity from Nuclear power or renewables to make liquid fuels. The title says it all "Sustainable hydrocarbon fuels by recycling CO2 and H2O with renewable or nuclear energy" what part of nuclear and renewables don't y'all get.

That said it seems that unless they get the electrolosis costs down only 98.5% 27/7 Nuclear 1.5-3 cent per kWh power is going to be even remotely economical. So lets build lots of modular nuclear plants that once the plant design is certified the greenies cannot sue anymore to stop its construction, build one plant design thats certified and be done with it, Hyperion is going to lead that push with there mini reactors that can be transported in NRC certified Fuel casks over land rail+truck & sea modes of transport once they get the cert done they can fordist the production process and crank them out by the hundreds and no one can stop them legally.

Thank God we got some sense about or permitting and operating laws now the NRC must issue operator licenses for precertified plant designs and fringe greengroups cannot sue endlessly litigating up the plant costs to the point where investors wont build them. Score one for the winning team of American nuclear power industry. Hyperion is estimating with mas production the busbar cost will be 4-5 cents per kWh thats 3 buck petrol I for one would pay 3 bucks any day over $2.70 for retail petrol. As long as it's 100% American made pure petrol not the E10 rubbish we get here. Content in the knowledge that not a single drop was from the middle east and none of my hard earned capital goes to those who despise our western high standard of living lifestyles, and frankly are openly hostile to this Nation and our very lives. Without our petrodollars let them eat sand, pull every troop out and let them without our funds for imported food and desalination descend to savagery amongst themselves.


sorry word messes up the copy n paste meant 98.5% uptime for nuclear reactors and 24/7 busbar power at full load. I have read the report we get access to Scidirect 3-5 cent power = 3 buck petrol if its 24/7 power only nuclear can do that for the price. Going to a standardized plant design would lower the costs even more for large plants 1-2 cents at the buscar is possible including 10% ROI and O&M costs for a gen 3 reactor.

Donough Shanahan

Ridiculous study. ABB currently puts the cost of carbon capture and storage from a coal plant (where it is in relatively high concentrations so easy to extract) at 25-35%. That means for 2 normal plants we need 3 CCS plant in terms of coal used. How the Danes propose doing everything else on what little energy is left is unfathomable.
Furthermore what is the point in comparing electricity to petrol prices; petrol is not used to make ele3ctricity (graph 1). Poor research.

Thomas Pedersen


It seems to me that they are implicitly thinking of using captured CO2. I certainly hope they were not thinking of capturing CO2 out of the atmosphere, which is even more proposterous!

So where else can we get concentrated streams of CO2, if not from the atmosphere or fossil-fueled power plants. Well, there are refineries and natural gas purification plants. These would be stellar candidates since they already have the infrastructure and expertise on site to run such plants. Tar sand processing plants also have large demand for hydrogen.

Cement kilns and metal smelting plants are other emitters of CO2 that would have a hard time using anything else for fuel.

IGCC plants and, as mentioned in my previous post, coal-to-liquid plants are also cadidates for using hydrogen from electrolysis rather than natural gas reforming or simply emitting or sequestering the CO2.

I am not a huge fan of coal-to-liquid fuels. I think downsizing cars and adding some battery power to further increase the mpg is a better way to prolong the 'fossil era'. Coal-to-liquid without carbon capture on the site, however, is tantamount to crimes agains humanity with all the established science on climate change. Yes, I agree it's not 100% proven but the risks are high enough to take precautions. It's a whole other story if at least all the carbon in the coal goes into the liquid fuels.

So TX I agree that for the US, it is better to start producing your own fuel (as well as downsizing your cars), rather than sending trillions of petro dollars to the Middle East.

So maybe this study wasn't so stupid after all...


Some people are thinking about capturing CO2 from the atmosphere.

K2CO3 + H2O + CO2 (air) -> 2 KHCO3

2 KHCO3 + heat (100-120 C) -> K2CO3 + CO2 + H2O

If you've got nuclear heat (or waste heat from another process) to drive this, it seems to be a decent way to concentrate CO2; from that CO2, you can make most anything. It's nothing close to competitive with batteries for energy, of course.


From the report they are taking in to account CO2 Air Capture this can also clearly be seen in the graphs above too. They include in the cost analytics capital cost for CO2 capture and the cost to electrolysis the resulting CO2 with water to yield syngas for FT. There was a similar report on this website no less that also shows with 1-3 cent busbar nuclear power CO2 air capture to fuel is economic at 3 bucks a gallon. Only nuclear power is cheap enough to do it no other form of primary energy has the economics to compete with ~$55bbl oil.

This is the most Eff way to get atmo CO2


"The minimum power consumption within the operation conditions studied in this
work was 0.57 kWh/kg-CO2 (or 0.57 MWh/t-CO2 equivalently), which was achieved at the
current density 2.4 mA/cm2"

570 kWh a ton at 2 cents per kwh for 24/7 co-site located nuclear power is $11.40 per ton of CO2 in electrolysis energy costs. The air flow needed across the carbonate solution could be combined with cooing tower system from the reactor a updraft cooling tower in natural draft mode moves massive amounts of air and water every second 24/7. using the waste heat to drive the convection updraft.

Also as EP pointed out K-carbonates dissociate at reactor waste heat temps so colocating the air capture next to the nuke site is a no brainer. Now stop building boutique reactors and Fing get on with the standardization process of plant designs and make the NRC issue operators licenses the time for endless litigation is over.


Ummm - are we getting lazy or has this entire thread not been published already??

Stan Peterson


I like that you noticed that Archaebacteria can use CO2, and convert it to Methane. But you don't have to create such a system, and Mankind couldn't on such a large industrial scale as currently exists.

It is already being done everyday; and has been for a billion years or more. Unknown to Scientists of only 15 years ago, there are gargantuan amounts of such Archaebacteria, working in the oxygen free places where they had to retreat to hide from killing Oxygen. They found a suitable home, under the oceans in the rocks from the ocean floor to over six miles deep into the rocks below. The aggregate weight of these Archaebacteria is enormous, aggregating to over 1/3 of the total mass of all life on Earth!

And all they do is reproduce, and convert CO2 to methane in enormous volumes, and turn some of that into their bodies as complex hydrocarbons. Both of which slowly begin the conversion to more complex hydrocarbons, on their death. The external energy they utilize is geothermal; and relatively unlimited, produced by gravi-metric contraction, and radioactive decay.

These hydrocarbons are known by another common name.
We call it Petroleum.

These discoveries contradict the fundamental assumption that the quantity of petro-hydrocarbons is fixed. The Earth's biosphere extended, is making more of it constantly, in relatively prodigious quantities. It does Not mean we should be profligate in the use of hydrocarbons. I will welcome the day when we no longer simply, burn it.

PS: Others misunderstood my comments about realistic feasibility. Certainly we could theoretically start with CO2, and synthetically manufacture more complex hydrocarbons to burn, while inputting lots of energy.

But we don't have the spare energy. We already do manufacture synthetic fuels, on an industrial scale,starting with a higher product produced by solar and bio-sequestration of CO2. Fully 15% of the USA transport energy is supplied by bio-fuels; but the making of those liquid bio-fuels consume lots of hydrocarbon energy from other sources. Our eco-loons would never allow the doubling or more, of the present energy supply to do it.

The eco loons, won't even allow the the construction of replacement of our current energy producing capital stock. Slowly it is degenerating in places like Hollyweird.

In particularly ridiculous eco-green loony lands, the citizens will soon discover that blackouts/brownouts are constant, and will take decades to remedy.


Henry Gibson

The DURATHON battery from GE will eliminate the need for much fuel for many trips that people take. Nuclear heat can replace coal heat in many power plants and free up coal to be used to make nearly conventional automotive fuels directly. Nuclear heat can replace heat from natural gas that is used to extract bitumen from tar sands. Even automobiles could be designed to capture CO2. The use of ammonia as a fuel would eliminate CO2 releases. An old prius can have DURATHON batteries installed for 100 mile electric range and they will be cheaper in large quantity. Alternators can be replaced with high power switched reluctance motor/ alternators in most cars to use part electricity all the time from batteries. ..HG..

Coke Machine

Henry I think using ammonia as an everyday fuel is just about as ridiculous as NASA scientists initially wanting to use Hydrogen Fluoride as a fuel in their rockets. Fuel release in an accident would be devastating. I remember when working at Tropicana Products in Bradenton Florida before they went to a glycol refrigerant system thinking that if they had a catastrophic ammonia leak, everyone up to Tampa (N) or Ft Myers (S) would be either dead or have extensive lung damage. They used a LOT of ammonia. Using ammonia would then have people complaining about the N02 being released instead of the CO2. Leaving off the Hydrocarbon or the Nitrogen and just using the Hydrogen would make much more sense. Yeah they all can explode, but at least the Hydrogen would dissipate faster and less hazardously than the Ammonia or the Hydrocarbons

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