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Audi in new e-fuels project: synthetic diesel from water, air-captured CO2 and green electricity; “Blue Crude”

Audi is active in the development of CO2-neutral, synthetic fuels; the company already has projects underway with Joule in the US for the development and testing of synthetic ethanol and synthetic diesel (earlier post); has an e-gas project underway in Werlte, Germany (earlier post); and has a new partnership with Global Bioenergies on bio-isooctane (bio-gasoline) (earlier post).

Audi’s latest e-fuels project is participation in a a pilot plant project in Dresden that produces diesel fuel from water, CO2 and green electricity. Audi and project partners including Climeworks and sunfire (earlier post) opened the plant today. The project combines two innovative technologies in this project, which is funded in part by the German Federal Ministry for Education and Research and was preceded by a two-year research and preparation phase: direct capture of CO2 from ambient air and a power‑to‑liquid process for the production of synthetic fuel. Audi is the exclusive partner in the automotive industry.

Other partners in the project consortium include Lufthansa; Fraunhofer ICT; Universität Stuttgart; Forschungszentrum Jülich; GEWI AG; CVT Chemical Engineering; and HGM.

The sunfire plant, which operates according to the “power-to-liquid” (PtL) principle, requires carbon dioxide, water and electricity as raw materials. The carbon dioxide is extracted directly from the ambient air using direct air capture (DAC)—a technology developed by Swiss partner Climeworks.

The Climeworks CO2 capture technology is based on a cyclic adsorption / desorption process on a novel sorbent. During adsorption, atmospheric CO2 is chemically bound to the sorbent’s surface. Once the sorbent is saturated, the CO2 is driven off the sorbent by heating it to 95 °C, thereby delivering high-purity gaseous CO2. The CO2-free sorbent can be re-used for many adsorption/desorption cycles.

Around 90% of the energy demand can be supplied by low-temperature heat; the remaining energy is required in the form of electricity for pumping and control purposes. The patent-pending technology has been developed in collaboration with the Professorship of Renewable Energy Carriers at ETH Zurich. The optimization of the sorbent and scale-up of the sorbent synthesis process is carried out in collaboration with the Swiss Laboratories for Materials Science and Technology (Empa).

In a separate process, a solid oxide electrolysis (SOEC) unit powered with green electricity splits water into hydrogen and oxygen. (sunfire acquired staxera, a developer and manufacturer of SOFC high-temperature fuel cells sited in Dresden in 2011.) The hydrogen is then reacted with the carbon dioxide in two chemical processes conducted at 220 ˚C and a pressure of 25 bar to produce a hydrocarbon liquid called Blue Crude. The process is up to 70% efficient.

Sunfire 2
Top: Two cartoons of the basic sunfire concept and process. PtL = Power-to-Liquids. Bottom: 3D model of sunfire SOEC (left) and the demo plant (right). Source: sunfire. Click to enlarge.
Sunfire 3

As currently built, the pilot plant on the sunfire grounds in Dresden-Reick can produce approximately 160 liters of Blue Crude per day. Nearly 80% of that can be converted into synthetic diesel. This fuel—Audi e‑diesel—is free of sulfur and aromatics, and features a high cetane number. Its chemical properties allow it to be blended in any ratio with fossil diesel—i.e., it can be used as a drop-in fuel.

The Audi e‑gas plant in Werlte, Lower Saxony, already produces synthetic methane (Audi e‑gas) in a comparable manner; drivers of the Audi A3 Sportback g‑tron can fill up on it using a special fuel card. (Earlier post.) Audi is also conducting joint research into the synthetic manufacture of Audi e‑gasoline with Global Bioenergies. And a joint project with Joule is striving to produce the synthetic fuels Audi e-diesel and Audi e‑ethanol with the help of microorganisms.

With this latest collaboration, Audi said, it and its partners are demonstrating that industrialization of e‑fuels is possible. The pilot plant was officially brought on stream today in the presence of Prof. Dr. Johanna Wanka, German Federal Minister for Education and Research, and Dr. Hagen Seifert, Head of Environmental Assessments, Renewable Energies and New Materials at Audi AG.



Massively stupid. Incremental electrictiy supply in Germany comes from coal, not green sources. It is a complete lie that the electrolysis part of the process is "powered with green electricity".

Making H2 with coal-based electricty at 70% effiency is already a complete waste. GOing further to make diesel by adding yet another lossy step of reacting CO2 with H2 is even worse.

Good thing it is just a toy plant that males only 160 liter/day.


It depends on when they turn the plant on.
If they turn it on from say 11-4pm in summer, they could well be using excess solar, if they turn it on at 6pm in the winter, this will not be the case.

Anyway, as you say, it is a toy plant for marketing purposes (160L / day).

+ imagine having the surname Wanka ... OK in Germany, not OK in English speaking countries.
Lucky she is a woman, so it won't be as bad.


You mean as in Willy Wanka? Wasn't there a biofuel called BioWillie? Just fill up with your Willie.

I note that this process just throws away the oxygen. That's a waste.


Only 160 liters a day ?? im amazed at so many millions or billions of dollars spend by goverments and car companies to displace so few petrol with their millions of subsidies to e-gas, batteries , hydrogen cars and stations, windmills without energy storage, etc. It cost 1000$ to save one barrel of crude petrol, that's a joke. I save myself more barrels of petrol by driving slow without impeding traffic and by having a small car instead of a big suv and it cost me nothing more and on the opposite im saving money.

On the next election, im voting for exxon mobil as president.


has projects underway with Joule in the US
Joule uses water, light, CO2 and nutrients to make diesel directly. Hard to beat that no matter how cynical.


Currently about 24% of Germany's grid energy comes from renewable, but that's a yearly average. If you cut the period to half a year that number goes up;

And they set single day records up to 75%;

And contrary to what the naysayers say it doesn't hurt the grid, it only drives the prices down;

Renewables are still growing so although this is just a toy plant that makes only 160 liter/day NOW by the time they are ready to produce more this will be a great place to dump their excess wind/solar.


@al Vin, Pulling records like this is easy.
2pm on a windy Sunday in August, you are up to your teeth in wind and solar.

Now flip the clock around to a still Tuesday in January at 4pm, no wind, no solar and lots of demand.
All you have is hydro, some biomass and the conventional stuff, and imports. So you have to keep all the old stuff going, and someone has to pay for it to be throttled right down in the summer.
The grid is under stress, but hasn't collapsed, and probably won't.
It has cost the conventional power producers 1/2 a trillion euros and ruined their businesses.
You may sneer and say they deserved it, but they are the ones keeping the lights on in winter.


@ mahonj
Just putting it mildly, I have an extremely strong dislike for monopolies. The power utilities in Europe, particularly in Germany, are all monopolies. I fervently hope, that renewables keep up - better yet - increase their pace and push those monopolies out of business. I can't wait to see all of them pushing daisies.


Well mahonj if you're going to try to use the old "we'll be freezing in the dark" myth I think I will sneer and say they deserved it. After all that right wing talking point deserves to be counter with another: Companies should be allowed to fail. The writing has been on the wall for decades, if the conventional power producers couldn't be bothered to prepare for the change they knew was coming by investing in new tech and operational paradigms then yeah, "they deserved it."


I am always amazed at the "free" market mavens who say the private sector will provide all we need. If you listen to that, which is NOT supported by history, we will all be left in a mess. Then the market mavens will not be around, they will be living with their money in off shore accounts.


The e-power mix is and will be changing in most countries. By 2100 it will probably be very different. REs will multiply and may very well become the major contributors.

Hydro will peak by the end of the century but wind and solar with storage could eventually supply 50% to 75% of our needs.

Conventional CPPS and NPPs will be phased out as early as 2050. A new generation of NPPs maybe used after 2050.

it doesn't hurt the grid, it only drives the prices down

A Sunday, when few people are at work.  In other words:  useless for meeting real needs.

After all that right wing talking point deserves to be counter with another: Companies should be allowed to fail.

Should companies have to pay less-capable competitors so that they fail in their favor?  And what happens when the essential services provided by the designated-loser companies go away?

Let production tax credits and feed-in tariffs go away, and THEN let's see how it shakes out.  Not one second sooner.


Only governmental boondoggling would waste a second with this pseudo-technology.

Its like the nuclear alchemists who said they could make Gold. Everyone was happy until they said you start with Platinum...

Call me back in a thousand years if you still need diesel. Until then I don't think the market wants to buy too much of this so-called answer at probably a $1000.00 per gallon.

I am amazed at just how quickly some of y'all are to sign up for idiocy such as this. The need for any of this nonsense has largely disappeared. Hydrocarbons are not in any danger of shortage for a Millenia or more. So-called "renewables", despite enormous subsidies, simply don't scale in size or price, to other energy sources.

The so-called CAGW need to limit GHG CO2 has disappeared as Dr. Ravell himself said back in the 1950s, when he was retracting the veracity of his earlier publications which are the only theoretical basis for CAGW in the first place.

History has proven CAGW induced Global Warming to be wrong in its temperature raising power. Reality has proven it virtually nonexistent for approaching 20 years now.

Yet you exist here in ever dwindling numbers predicting Doomsday; and wishing against reality for your no longer needed fantasy technologies to magically appear which contradict the Laws of Physics.

It is stupid to "unburn" diesel, spend scandalous amounts of energy to make the raw ingredients for diesel. And then spend prodigious amounts of energy to reconstruct diesel hydrocarbon chains.

All this to make a fuel you will then simply burn again.


Using clean e-energy to produce dirty diesel liquid fuel instead of clean H2 seems rediculous?

It is stupid to "unburn" diesel, spend scandalous amounts of energy to make the raw ingredients for diesel. And then spend prodigious amounts of energy to reconstruct diesel hydrocarbon chains.
All this to make a fuel you will then simply burn again.

Truer words... and for climate hawks, completely wrong-headed because the fossil carbon still goes to the atmosphere.


To quote the article: "The carbon dioxide is extracted directly from the ambient air using direct air capture."


Using clean e-energy to produce dirty diesel liquid fuel instead of clean H2 seems rediculous?

Agreed. . . for MOST applications. Using battery stored energy is the most efficient way, and H2 would be great as a range extender. But there are times when space is at a premium.


When it's still prohibitively expensive to recover CO2 from seawater, and seawater is much easier to extract it from than air, I'm going to bet that the only way this will go forward is if the carbon comes from FF power stations.

Over at The Energy Collective, it's been noted that the Energiewende was supposed to be financed by the utility companies, but those very companies are being bankrupted by the Energiewende's tariffs and other policies.  In short, it's on a one-way track to death.  It's the same for schemes like this.


Once the technology is fully commercialized, Joule aims to produce 25,000 gallons of synthetic ethanol and 15,000 gallons of synthetic diesel per acre annually, for as little as $1.28 a gallon and $50 a barrel, excluding subsidies.


Remember Range Fuels, and their projections of ethanol production from biomass via chemosynthesis?

Refresh your memory.


Irrelevant. My early point still stands: Few transportation fuels surpass the energy densities of gasoline and diesel. Energy density and the cost, weight, and size of onboard energy storage are important characteristics of fuels for transportation. Fuels that require large, heavy, or expensive storage can reduce the space available to convey people and freight, weigh down a vehicle (making it operate less efficiently), or make it too costly to operate, even after taking account of cheaper fuels. Compared to gasoline and diesel, other options may have more energy per unit weight, but none have more energy per unit volume. Even if it did end up costing more some people will be willing to pay for the advantage of having more energy per unit volume.


"Large, heavy" (~6% useful content by weight) and "expensive" epitomizes the "alternative" of H2.  Anything made from "renewable" H2 is still very expensive.

Energy per volume is useless if you can't afford it.  Energy per dollar is a major factor until time is affected.  If you can't get enough energy per unit time, other options are preferable.

If volume is cheap, people won't care about low volumetric energy density.  The English put town-gas bladders on their cars in WWII and couldn't have cared less about the bulk.  Worry about the things that matter.


English put town-gas bladders on their cars in WWII and couldn't have cared less about the bulk.

Bullpucky. My grandfather actually did that, and like the rest of his countrymen he pulled that junk off his car after the war just as soon as gasoline was available again. It's not that they "couldn't have cared less about the bulk" it's that they had no other options.


"It's not that they "couldn't have cared less about the bulk" it's that they had no other options."

Or more likely, put up with it for the greater good of the war-effort.


In other words, they wanted things to be "normal" again.  Thing is, we're not going to have "normal" (as in 1950's-70's) petroleum prices or climate conditions during the lifetime of anyone alive today.

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