BBC: Could diesel made from air help tackle climate change?

[nationalize the fed]

BBC Padraig Belton

Making diesel out of thin air sounds like something from science fiction.

But small companies in Germany and Canada are doing precisely this - capturing carbon dioxide (CO2) and finding ways to sell it.


How a large-scale carbon dioxide capture plant might look

German company Sunfire produced its first batches of so-called e-diesel in April. Federal Minister of Education and Research, Johanna Wanka, put a few litres in her car, to celebrate.

And the Canadian company Carbon Engineering has just built a pilot plant to suck one to two tonnes of carbon dioxide from the air daily, turning it into 500 litres of diesel.The process requires electricity, but if the start-ups use renewable electricity they can produce diesel that is carbon neutral...

Price at the pump

...But a lot depends on government policy. The actual price of the fuel can be as low as 30% of what we pay at the pump - the rest of the cost is made up of fuel duty, VAT, and the retailer's profit margin...snip
full article: http://www.bbc.com/news/business-34064072

[Kelvin Mace]

1. Sounds WAY to good to be true

I would need to see some independent review of the technology and a look at the numbers. It takes a Hell of a lot of energy to heat anything to 800-900C.

[AtheistCrusader]

2. Exactly. More energy put in than you get out of it.

It is a way of storing intermittent power like wind and solar. Seems a shame to re-release that carbon as burned diesel though.

[cheapdate]

3. An array of positionable high quality mirrors with accurate motion controls

can produce those temperatures on a sunny day. Motion controllers keep all of the mirrors maximally focused on a central point where the heat transfer fluid is heated.

[Kelvin Mace]

6. From what I saw of the device

it didn't have such a mirror array and they talk about using electricity:

The process requires electricity, but if the start-ups use renewable electricity they can produce diesel that is carbon neutral.

So, that's a LOT of electricity. They are claiming they can sell it for roughly $5, which raises a lot of questions for me since simply producing a kg of hydrogen by electrolysis is about $18 a kg and this process is WAY more complicated.

These pellets are then heated to 800-900C, whereupon they release a pure CO2 stream. As a residue, they leave calcium oxide which, handily, can be fed back in to the first air capture stage.

My back of the envelope calculations requires about 3.2 mW of electricity just for this step. The best solar panels can yield about 200 watt per sq m, so we need about 3,200 sq m to produce that much power, assuming a 5 hour average window of sun.

And that would set our production at 500 liters per day (about 116 gallons) or enough to fill up about 11 cars.

The BBC is reporting claims made by a private company. I will remain skeptical until their process is independently verified.

[Binkie The Clown]

4. Less efficient that direct use of the electricity

Suppose you just put that electricity into the grid, or into a battery.

But no, they propose taking the long way around the mulberry bush, introducing more inefficiencies with every step.

Why not do it this way: Generate renewable electricity and use that electricity to run a motor that pumps water from the ocean up to a reservoir on a mountain top, and they run that water through a hydro electric plant to generate electricity to hydrolyze water into hydrogen and oxygen and then use the hydrogen to run a fuel cell that powers a fan that blows at a wind turbine that generates electricity to run a still that distills corn mash into alcohol and power the cars with alcohol?

The reason that's ridiculous should be obvious.

Every conversion step you put between the generation of renewable electricity and the use of that electricity for transportation, adds more inefficiency to the system. In other words, every extra stage wastes more energy. Using electricity to turn CO₂ into fuel to run a vehicle has to be more wasteful than using that electricity directly. It's the laws of physics, and you can't cheat the laws of physics.

[kristopher]

5. They don't want to cheat the laws of physics...

...things like this flow from and go along with the desire to build lots and lots and lots of nuclear plants.