Apr 28 2015
Audi’s E-Diesel
Audi has been working on a synthetic diesel fuel and is currently producing test samples, with plans for industrial production. This is potentially a useful technology (depending on the details) but, as is almost always the case, is widely misreported.
For example, Gizmag states: “Audi just created diesel fuel from air and water.” Farther down in the article they do mention that you also need another critical ingredient – energy.
Engadget reports: “The automaker recently produced its first batch of “e-diesel,” a synthetic diesel based solely on carbon dioxide and water — readily available chemicals that are far nicer than sulfur and other typical diesel elements.” They never make mention that the process requires energy.
I don’t think this is a nitpick, because already the Audi story has been mentioned to me by someone who did not understand, until I pointed it out to them, that processes such as this are not a source of energy or fuel, they are simply an energy storage medium. Saying that fuel is made from “carbon dioxide and water,” while not wrong, is incomplete and fosters a fundamental misunderstanding of what is going on.
The same reporting occurred last year when the US Navy announced their plans to make fuel from seawater. Science.dodlive reported, “Energy Independence: Creating Fuel from Seawater.” That was one step more misleading by invoking the notion of energy independence.
The same confusion remains common around hydrogen fuel. Since we have little free hydrogen on earth, hydrogen is not a fuel source, just an energy storage medium. If someone is advertising an engine that can run on water you can be almost guaranteed that what they are doing is electrolysing water into hydrogen and oxygen, then burning that hydrogen back with oxygen. Of course, the laws of thermodynamics ensure that it costs more energy to electrolyse the water than you get back when you burn the hydrogen with oxygen.
The analogy that seems to get people to understand what is going on most easily is that of a battery. No one claims that batteries will make us energy independent because we can run cars on batteries. They more intuitively understand that you need an energy source to charge the batteries. The same is true of synthetic fuels, including hydrogen.
Synthetic fuels are still useful, however. In the case of the Navy, they were not looking for an energy source, but a way to use the power generated by the nuclear reactors on aircraft carriers to make fuel that can then be dispensed to smaller support craft that don’t have their own nuclear power plants.
The big advantage to synthetic fuels, including Audi’s new e-diesel, is that they are carbon neutral in themselves. In the case of the Audi process, they start by using an energy source to electrolyse water into hydrogen and oxygen. They then combine the hydrogen with carbon dioxide taken from the air, creating what they call blue crude. This undergoes further processing into e-diesel. Right now their pilot plant can make about 1,000 liters per month, which is nothing. They will need to ramp up to industrial scale production, something which can never be taken for granted.
The e-fuel, like bio-fuels, is carbon neutral because it takes carbon out of the air and then puts it back when burned. Fossil fuels are a problem because they take carbon sequestered under ground and add it to the carbon cycle, increasing the amount of carbon in the atmosphere.
There are always two major factors that need to be considered, however. The first is – what is going to be your energy source? Stories, like all the stories about the Audi fuel that bother to even mention the need for an energy source, always say that renewable energy sources will be used. That is not something that can blithely be taken for granted, however. Having a massive renewable energy infrastructure is a bigger deal than the ability to use that infrastructure to make synthetic fuel. We could also use it to recharge batteries, or run our homes.
I would like to see hard numbers on how much energy production would be necessary to displace fossil fuels in cars. I suspect it will be challenging. In fact we may need nuclear power plants to produce enough energy to replace a significant amount of fossil fuel with synthetic fuel.
Making synthetic fuels does have an advantage, however. They can be a useful energy storage medium because the renewable energy does not have to be distributed, it can be used where it is made, assuming the fuel plant is located where the renewable energy is made. Also, the energy does not have to be on demand. The plant can simply run when the sun shines or the wind blows.
Also, synthetic fuels, if they are compatible with existing cars, can be used without needing to add any major new infrastructure. Simply convert pumps at gas stations to synthetic fuels, and fill up your tank. They also avoid the problem with batteries of recharge time, or adding a new infrastructure to swap out or recharge batteries.
The second major factor to consider is the efficiency of the entire process, from plant to car. If the process is inefficient then it may use too much energy to realistically scale up. This is the ultimate limiting factor with biofuels – getting the process efficient enough. One way to measure overall efficiency is cost. How much will a gallon or liter of e-diesel cost?
I suspect this is mostly why, even though we have been hearing about synthetic fuels for decades, we aren’t running our cars on synthetic fuels today. How are we going to power the whole process, and can we produce it efficiently at industrial scales so that it will be cost effective?
Because of anthropogenic global warming, however, the question can be reframed as – how much are we willing to spend for a carbon-neutral synthetic fuel to avoid pouring more carbon into the atmosphere? What may happen is that governments will subsidize the production of synthetic fuels to bring their cost down to a level that is competitive with fossil fuels. Eventually, through rising fossil fuel costs or improvement in efficiency, synthetic fuel costs may become competitive on their own.
None of the reporting on Audi’s new e-diesel that I have seen mentions any of these issues or gives us any numbers on cost, efficiency, or needed energy infrastructure. Those are the details, however, that will ultimately determine the success or failure of this endeavor.
17 Responses to “Audi’s E-Diesel”
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This article hits all the right notes as far as thinking of synthetic fuels as energy storage. The ultimate source of energy and the amount consumed in the process must be considered. (This is why the tar sands in Canada are doubly horrible – they take an enormous amount of energy to process into usable fuel, which is a fossil fuel, so MORE carbon is released.) Production of synthetic fuels is a good match for intermittent renewable power sources. Seems like the killer in this process for now is electrolysis, which is energy inefficient. There’s a lot of work going on there, trying to improve electrolysis and make ‘artificial leaves’ which will go straight from sunlight to cracked H20. Alas, I currently give those articles the same weight as battery tech ‘breakthroughs’. I’ll believe it when it becomes practical.
Synthetic fuels will probably be unnecessary as an auto fuel in the long run, because I believe that electric cars will rule the day once battery tech comes along enough. Things like jet aircraft, rockets and heavy load vehicles are unlikely to be candidates for electric propulsion any time soon, so there will always be a need for liquid fuels.
Thanks Steve for bringing up nuclear power. I personally feel that this will be the way forward for civilization – nuclear reactors as the source with batteries and e-fuel as the medium. Don’t get me wrong, solar and wind power will always be in the mix, but they pale in comparison to the gigawatt scale that nukes provide. From listening to the show, it sounds like batteries are never going to be energy dense enough to be practical on airplanes, highway trucks, or cargo ships so having the technology to create diesel with electricity is a good thing.
This is really cool. I wonder if this causes less pollution to manufacture than electric car batteries?
@GWD, probably not. Audi says they achieve 70% efficiency in the creation of the fuel, which is then burned in an engine at roughly 40% efficiency. Batteries have their own losses like idle discharge and the fact that they’re heavy, but they probably still win out since their charge/discharge efficiency and the efficiency of the electric motor are both well over 80%.
I drive a Volt. When I am not burning gasoline, I am burning a mixture of Coal, Natural gas and about 20%Wind. My emissions may be down locally but they are moved somewhere else. I like driving an electric car since it has a lot of low speed pickup and great handling, but I do not fool myself into thinking that I am solving the energy problem. I am just changing the mix. If I put solar panels on the roof at home, I might actually be doing something.
GWD –
The manufacturing process of e-diesel can probably be made far less polluting than the complete life-cycle of a lithium based battery. In addition, it’s probable e-diesel will be easier to store and distribute than batteries — you have to have the energy available to charge them when they need charging, and even the best batteries incur significant energy loss over time. So e-diesel’s overall efficiency might be a lot closer to batteries than suggested by the raw efficiency figures.
This type of fuel can never be carbon neutral. That would violate the second law of thermodynamics. It is, however, far less of a carbon emitter than burning fossil fuels.
Was any statement made about how much less carbon would be emitted by burning this fuel than fossil diesel?
> Michael Finfer, MD
> This type of fuel can never be carbon neutral. That would violate the second law of thermodynamics.
Well, theoretically, if the power source used to produce it is 100% carbon clean, and the process itself captures carbon dioxide out of air (which I don’t know whether it does), then the inefficiency doesn’t matter with regards to carbon neutrality: all of the carbon dioxide released into atmosphere by burning it in an (inefficient) engine was previously captured by the process, making it fully neutral.
All of the above becomes irrelevant in the real world where electricity production isn’t yet 100% carbon clean, and where cost of the production matters. But, in theory, it can be a carbon neutral fuel.
What a life saver for the Audi business plan. One thing to remember is that nothing about luxury German cars is cost competitive. Even without government subsidizing you could imagine folks driving these low MPG cars and not minding the extra expense to do so cleanly (at least in Germany).
It’s funny I only read the Audi press release and it sounds like I was better off than reading the media reports.
> Even without government subsidizing you could imagine folks driving these low MPG cars and not minding the extra expense to do so cleanly (at least in Germany).
Even worse, it wouldn’t be even remotely clean in Germany because 53% of their electricity comes from fossil fuels, so “burning f.f. to make electricity to make fuel to burn it in internal combustion engines” probably makes a lot less sense than just directly “burning fossil fuels in internal combustion engine” due to losses in the first case. But then, in France or Norway for example, it could be another story – depending on the efficiency of the process.
In some countries, it is even less green to drive an electric vehicle compared to an efficient oil-based-fuel one – it all depends mainly on where the electricity comes from. Here’s a nice article on the topic: http://shrinkthatfootprint.com/electric-cars-green
Thanks for a great link Mr Qwerty. I would note, however, that the overall conclusions of the article are very positive regarding electric vehicles. In California, for example, an electric car is equivalent to a 70 mpg conventionally fueled car.
Also, John Timmer at Ars Technica has a well written article on this topic which actually discusses the energy requirements for this fuel in some detail.
http://arstechnica.com/science/2015/04/27/audi-samples-diesel-made-directly-from-carbon-dioxide/
@DS1000:
In a transitional period, sure, but at its core, nuclear is just another limited resource. It will run out, it’s just a matter of when. At the end of the day, we have to focus on the pure renewables; wind, solar, wave.
Admittedly, I’m not sure of the time horizon for nuclear, nor how soon we can get the renewables online in a cost-effective way. However, I think we’d be best served going for the long term as soon as we can.
Frankly, I’m rather skeptical about investing a lot of money in short-term (even if that means fifty years or more) infrastructure. Seems to me that the same money is better sent on developing the renewables.
Michael Finfer,
“This type of fuel can never be carbon neutral. That would violate the second law of thermodynamics.”
As Mr. Qwerty intimated, you are confusing two completely separate issues.
If all the carbon you use is taken out of the atmosphere and if it is all returned to the atmosphere, then that process is carbon neutral. Carbon neutrality has nothing to do with the second law of thermodynamics.
@Lukas Xavier: Strictly speaking you are correct, and I agree that we should be developing solar and fusion technology, but the time horizon on nuclear power with current reserves and no reprocessing is a few centuries with continually increasing usage. With breeding, reprocessing, and reasonable mining projections you have 100% global supply for ~500 years. That’s nothing to sneeze at.
Situations like the ones in iceland where you have a cheap abundant sources of energy and try to capture and reuse co2 make a lot of good sense.
George Olah CO2 to Renewable Methanol Plant, Reykjanes, Iceland
http://www.chemicals-technology.com/projects/george-olah-renewable-methanol-plant-iceland/
For the rest of us I suspect these technologies won’t be practical unless we make better safer use of nuclear fission or advance nuclear fusion technology to where it’s practical.
It would be interesting to know just how energy dense the blue diesel is. For instance refined gas weighs roughly 6lbs per gallon where as diesel weighs closer to 8lbs per gallon. Which I assume is why you can get so much more work done with a gallon of diesel than you can with a gallon of refined gasoline.
We already have almost limitless fusion power: the Sun. think about how tiny a fraction of the Sun’s power actually lands on Earth, and yet it powers our entire ecosystem. (What I mean by tiny fraction is: consider a sphere 150 million kilometers in diameter, now calculate the surface area of that sphere. Now, as a rough calculation, subtract the area of the Earth. It hardly makes a dent in the area of the giant sphere, at Earth’s distance from the Sun.) Almost the entire output of energy from our gigantic fusion plant in the sky is thrown away into space.
The point of the physics exercise is to show that, as humans, we do not need to fret about renewable energy. Just build solar power satellites. As long as the Sun is active, we will have all the power we need. (We don’t need a Dyson sphere just yet.) See the 1975 study done by NASA. If memory serves, we could have developed the infrastructure already, and built the first two satellites, for only 200 Billion USD (1975 dollars).
The project uses raw material from the Moon. Solar-powered smelters break the moon rock down into Aluminum, Silicon, Oxygen, and other elements. Use the Aluminum for structures, the Silicon for solar cells, and the Oxygen for just about everything from rocket fuel to making water. Oh, and you can breathe it, too! Slag makes a great shielding material. They didn’t know it at the time, but they hoped for ice at the Lunar poles so that there would be ready supply of Hydrogen. Well, now we know that there is ice at the Lunar poles, so that is a plus.
The material can be lifted from the Moon using electromagnetic rail gun technology. With no atmosphere, the rails can be built on the surface and launch raw materials practically free — using solar power for the electricity. Nighttime on the moon? Just build more than one solar collector farm, or more than one catapult/collector complex.
So, once the infrastructure is in place: moon mining and launch catapults, orbital smelters for ore processing using solar parabolic mirrors (only need mylar for that!), orbital habitats for the work crews, and the first satellite — then you can just crank out satellites galore. They are in geostationary orbits — you build ‘em where you want ‘em, so you don’t have to move ‘em!
If memory serves, the design that they used projected 10 GW of power per satellite to large microwave receivers on Earth. It was dispersed over a large area of unused land or range-land or ocean. Safe for humans underneath the reception grid. 200 satellites would deliver 2000 GW of power continuously to Earth.
Now I’m ready for the naysayers: “you gotta think long-term, gentlemen, or you will fail utterly.”
There are ancillary benefits:
This is a much better use of money than trying to start up a Mars colony. The technology lessons learned in the Lunar endeavor will work for a Mars colony also, so there is a benefit there, too. The infrastructure in orbit can be used to build large interplanetary craft. The cheap rocket fuel from the Moon will allow large tanks and nearly constant-boost spacecraft. How about a trip to Mars that only takes a couple of weeks, instead of several months?
—-Thanks for listening…
A futuristic just so story, but hey!