Splitting Water For Fuel While Removing CO2 From the Air (arstechnica.com)

An anonymous reader quotes a report from Ars Technica: A new study led by the University of California, Santa Cruz's Greg Rau highlights another tool for our CO2 removal toolbox: splitting seawater to produce hydrogen gas for fuel while capturing CO2 with ocean chemistry. In electrolysis, a device powered by electricity is used to split H2O, producing hydrogen gas. Several chemical modifications to this process have been proposed that can also grab CO2 from the atmosphere. Like the idea of using biofuels, this represents a "win-win" by producing an energy resource while capturing CO2, bringing the cost down. [T]he gist is that atmospheric CO2 goes into the ocean as bicarbonate -- which won't acidify the water or harm ecosystems. So if you power the electrolysis process with renewable energy, you can turn solar/wind/hydroelectric energy into hydrogen fuel while also removing CO2 from the air.

The new study focuses on a basic estimate of the cost and maximum potential of this technique. First, the researchers worked out its efficiency of CO2 capture -- about 0.3 tons captured per gigajoule of electricity input, including the losses from quarrying and crushing rock. That's around 10 times greater than biofuel schemes, but it depends on the assumption that there is demand for all the hydrogen fuel you make. The hydrogen can be used by vehicles, and there's the possibility of using hydrogen as a type of storage for the electric grid -- using excess power to make hydrogen that can run a power plant when needed. So it's not too farfetched that demand could rise to meet supply. The researchers' back-of-the-envelope estimate puts the cost of this system at between $3 and $161 per ton of captured CO2, depending on which type of renewable energy powers it. The study has been published in the journal Nature Climate Change.

Comments

Bad Chemistry

[methano]

The gist that atmospheric CO2 goes into the ocean as bicarbonate and won't acidify the water is not correct.

Too early

[religionofpeas]

If you're generating electricity, it's much more efficient to use that to charge electric cars, and reduce the amount of CO2 that goes into the atmosphere, rather than using inefficient methods to get it out.

Also, hydrogen fuel is a dumb idea. There is no infrastructure, conversion/storage is inefficient and it makes metals brittle. It's much better to focus on electric battery cars.

Re: Too early

[c6gunner]

If you're generating electricity, it's much more efficient to use that to charge electric cars, and reduce the amount of CO2 that goes into the atmosphere

It depends on what your goals are. Even without looking at their numbers I can safely guess that this will be less efficient and therefore more expensive than just using batteries. So if your goal is to have the cheapest low-emission energy possible then yeah, batteries are better. On the other hand, if you're more worried about recapturing some of the carbon we've emmited over the last century or two and are willing to paya bit more towards that goal, then this technique might make more sense.

Whether or not it makes sense even in the latter scenario will depend on just how much more expensive it happens to be. We won't know that until they've done a lot more work on this tech.

Re: Too early

[religionofpeas]

That's why I said "too early". While we still have most cars producing CO2 from fossil fuels, it makes no sense to start recapturing. Recapturing combines an inefficient process at one end (cars generate a lot of CO2 for little energy output) using an inefficient process at the other end (use a lot of energy to recapture a small amount of CO2).

When all the low hanging fruit is gone, we can start worrying about recapture, preferably using a process that produces something more useful than hydrogen.

Re:Too early

[mjwx]

They want hydrogen cars to be big because they missed the boat on battery electric and a lot of the basic tech is now owned by other companies. They are facing either having to delay their EVs to wait out the patents or pay royalties, and all the while need to do their own EV R&D to avoid falling further behind.

Battery electric has already won. We already have 99% of the infrastructure in place.

Maybe in Hipster Central, SoCal... But out here in the real world 1% of the infrastructure isn't even in place.

Also my time isn't free. Spending an hour recharging just go to the 5 miles to home is a huge waste. If someone manages to produce hydrogen from seawater cost effectively, battery cars are effectively dead.

Re:Too early

[sfcat]

They want hydrogen cars to be big because they missed the boat on battery electric and a lot of the basic tech is now owned by other companies. They are facing either having to delay their EVs to wait out the patents or pay royalties, and all the while need to do their own EV R&D to avoid falling further behind.

Battery electric has already won. We already have 99% of the infrastructure in place.

Maybe in Hipster Central, SoCal... But out here in the real world 1% of the infrastructure isn't even in place. Also my time isn't free. Spending an hour recharging just go to the 5 miles to home is a huge waste. If someone manages to produce hydrogen from seawater cost effectively, battery cars are effectively dead.

The most common place to charge your EV is at your home. Generally, unless you are taking a road trip its difficult to need to charge anywhere else. You don't have electricity at your residence? In cities where you might only have street parking EVs are more of a problem. In suburbs or rural areas you have plenty of your own parking and likely have an outdoor plug already available. The only real infrastructure is something like the supercharger network where its available along major transportation routes. I still think it wouldn't be that practical to use an EV as your only car if you take road trips but we are getting much closer and if and when EVs reach more market share, you will see charging popup to fill the demand.

As for hydrogen, we are basically nowhere when it comes to infrastructure and it introduces a huge inefficiency into the energy cycle.

Carbon neutral fuels

[Martin S.]

If renewable energy such as off-shore wind farms were used we could achieve carbon neutral hydro-carbon fuel, we could even pump the spare fuel into natural crude oil reservoirs for carbon capture.

We get to keep our gas guzzlers with a clear conscience.

Re:Awesome

[divide overflow]

So assuming the low-end cost of $3 per ton of CO2, we're talking a mere $3,030,000,000,000 to mitigate anthropogenic CO2 emissions Sounds like just the type of pragmatic negative emissions technology we so desperately need!

Until you can quantify the costs of *not* mitigating anthropogenic CO2 emissions or identify the value of this method relative to that of other mitigation techniques it is impossible to gage the absolute value of this particular method.

Re:3 cents/gallon tax could recapture its CO2? Rig

[Anonymous Coward]

But you forget that 20 pounds of water vapor is also created! It's the the water vapor that is the problem not the CO2. It's the water vapor that causes the "greenhouse" not the CO2.

Re: Clean water?

[Anonymous Coward]

I don't really know what you are getting at here but there is a nice pro-tip in here.
If your beer tastes like piss when it is lukewarm and decarbonized then it tastes like piss when it is cold and fizzly too.
You are just able to swallow it before you get the taste of it.

So if you want to find out which beers are actually good, pour them up and let them sit for an hour or two.
If it still tastes good after that it is an actual drinkable beer that you can serve your visitors without feeling ashamed.
They might still not like it, but then it is a matter of subjective taste rather than you not having actually knowing what a good beer is.