Audi e-diesel fuel - synthetic fuel made from water, CO2 and renewable energy

[kamold]

https://www.audi-mediaservices.com/p...he_future.html


This would seem to be MASSIVE news, not sure why its not front page of mainstream newspapers?
If it scales it makes use of all existing transport infrastructure, and removes the cost of crude oil extraction from the equation.

[gldgti]

Very exciting! Thats really a huge step forwards - creating a liquid fuel from abundant energy and gasses in the atmosphere. Liquid fuels are so much more flexible than batteries!

Mind you, the amount on clean energy required will be significant, but thats not to say its a bad thing - the clean energy infrastructure programme around the world needs to get a lot bigger just to be able to provide electricity for everything else - this would be just like another industry. This is where biodiesel wins out in terms of the energy cycle, because you are utilising plant molecular processes in order to harness that clean energy.

[wai]

It is interesting, but the problem is that we do not have an oversupply of wind and solar power. If anything we have a shortage of wind and solar power.

The result is that you end up using gas or coal to generate the electricity to convert carbon dioxide and water into a "diesel" fuel.

What would be great is if Audi built a plant powered only by wind and solar to see how viable it actually is.

The other thing is that diesel as is used in vehicles is far more complex than just creating chains of hydrocarbons.

In an oil refinery, the crude is first distilled into its various fractions, there can be an excess of the heavier fractions and you also get lighter fractions. The heavier fractions are then put through a cracker where they are broken into shorter chains similar to the initial diesel. This then goes through a recombiner where the cracked chains and the lighter fractions are joined back again, however what gives you things like cetane numbers we need sees these short fractions added as side branches rather than added to the end.

So, diesel as we use it in our cars and trucks goes through a complex process and while the Audi process will produce a "diesel" fuel, it is not like what is used in diesel engines.

As I said, it needs to be investigated, but this has to be in a plant that uses only wind and solar energy to produce the diesel we need.

The ultimate is to have bacteria to use carbon dioxide and water to produce the diesel feed stock we need for our engines. Maybe that is really where the research needs to be.

[wai]

This is where biodiesel wins out in terms of the energy cycle, because you are utilising plant molecular processes in order to harness that clean energy.

Actually, bio-diesel from seed oil actually uses more energy to produce the fuel than the fuel is ever going to release.

The paddock has to be prepared and you need pre and post emergent herbicides to ensure the yield needed. Then there is the planting and husbandry of the crop. Next the harvesting and transporting to the processing facility. Once the seed is separated, it is crushed. The oil does not drip from the paste, but has to be heated for it to flow. It then goes through further energy demanding processes.

The only advantage you can gain from a bio-diesel is if it is produced for some other purpose (like frying fish and chips) and would otherwise be disposed of. But even here, there is a catalyst needed and there is a waste product that needs to be disposed of.

Again, diesel as we use it in our vehicles is a lot different to bio-diesel.

By the way, the energy consumption in the production of ethanol is also an issue. Just because it is grown rather than mined, does not necessarily make one cleaner than the other. The ultimate goal is to produce a fuel that sees an overall reduction in emission of CO2. There is little point in doing something that sees a net increase in CO2.

[gldgti]

Apologies for my previously simplistic post.

The only advantage you can gain from a bio-diesel is if it is produced for some other purpose (like frying fish and chips) and would otherwise be disposed of. But even here, there is a catalyst needed and there is a waste product that needs to be disposed of.

Your point about the energy required to produce the crop is a valid one, but you are assuming that all the energy used up in the process chain 'produces' CO2, which is rather short sighted. I'll deal with your point about the catalyst and waste product first, though.

To manufacture biodiesel you need around 20% by volume methanol or ethanol, and sodium hydroxide solution (the NaOH qty is pretty small). This is the catalyst.

Once you have biodiesel, you have around 20% by volume of the 'waste product', which is actually mostly glycerine and free alcohol - anything else is either unreacted oil (which can be recycled) or foreign contaminants. The alcohol can be reclaimed by distillation, and you see reclamation rates of around 25% by volume of what is required to manufacture the biodiesel. Glycerine is an industrial chemical used in all kinds of household goods and can be re-used. So unless you start with oil full of contaminants, you dont really have a waste product to deal with, you have an industrial resource.

Regarding the energy cycle... If you look at the production of any kind of liquid fuel assuming that the overall process should have less energy input, there will be some clear winners ofcourse. The goal you mention, is having a net reduction in CO2 emission.

Audi's e-diesel might be seen wholistically as carbon neutral, because they are using carbon already released into the atmosphere to 'build' the fuel, and they are proposing using clean energy sources to 'build' it (i.e. solar, wind etc).

If you want to compare biodiesel in the same manner, then its only fair to assume you are using the same clean energy resources to produce it - and theres no reason it can't. There are much more efficient methods of producing feedstock oil than using seeds, as you mention. So ultimately, you also have another carbon neutral fuel if you compare them on the same footing where the processes use clean energy, and who knows what when you utilise fossil fuels in the production.

I'm not sure I see your point about the fuel itself - or about the types of diesel. There is no reason a diesel engine cant run on a variety of fuels. If you put barrys homemade biodiesel in a brand new audi, you might (or probably will) end up with problems with emissions system components after a time (as you do with regular diesel anyway), but the engine will produce plenty of power and be economical, within reasonable deviations. Theres a lot manufacturers could do to make modern diesels more tolerant of varying fuel - and since passenger cars are considered consumable by the manufactuerers, then the fuel that is getting around today is not necessarily an indication of what will be acceptable or required tomorrow.

The whole point being, audi's e-diesel is at a pretty infant, but lets say promising development level, and just adds another option to the list of methods to produce a liquid fuel that is carbon neutral - its a pretty important list, because as nifty as electric cars are for city dwellers, you can't (yet??) fly a 200 tonne aircraft at 900km/h across the world on battery power.

[gldgti]

Actually, bio-diesel from seed oil actually uses more energy to produce the fuel than the fuel is ever going to release.

I can't help giving special mention to this - it doesnt matter what you are making - if it produces more energy than it took to create, you have just broken physics.

You might use less energy to drill the hole from which crude spills than it contains, but crude oil represents a huge amount of solar energy stored by biological processes over millions of years. People tend to forget where and when the energy was harnessed.

[wai]

I can't help giving special mention to this - it doesnt matter what you are making - if it produces more energy than it took to create, you have just broken physics.

You see, the process of producing a feed stock can be spread over millions of years, or be accelerated by trying to achieve it is an extremely short time (almost instantaneous in geologic time), and this is the issue.

With crude oil, the energy to get it to the initial stage has already been accounted for over millions of years. With the bio-fuels, we are trying to compress this into a few months, and so that energy has to be expended almost instantaneously. We do not have the time to spread this energy use.

But, you know, I have no issue with bio-fuels at all. What we need is the full picture put out there.

Digressing a little, even things like PV solar panels have questionable value when you look at the actual production of the panels and the supporting hardware. There are doubts as to whether the energy that goes into producing the system will ever be recouped by the electricity that that system will ever generate. The thing is that people who buy them do not understand this.

This is why I said that someone needs to build a pilot plant that operates only on wind and solar to see what the yield will actually be, and then how the fuel it produces can be used. It would be great if it could happen, however the chances are it will come up against barriers that will see it as a good concept but that had issues being made to work.

[Elmura]

Any manufactured liquid fuel is going to be more costly than mining fuel, both in dollars and pollution generated. Unless the manufacturing process uses free energy sources for some of the production