Removing CO2 From the Air Efficiently

Canadian scientists have created a device that efficiently removes CO2 from the atmosphere. "The proposed air capture system differs from existing carbon capture and storage technology ... while CCS involves installing equipment at, say, a coal-fired power plant to capture CO2 produced during the coal-burning process, ... air capture machines will be able to literally remove the CO2 present in ambient air everywhere. [The team used] ... a custom-built tower to capture CO2 directly from the air while requiring less than 100 kilowatt-hours of electricity per tonne of carbon dioxide."

Mine is far more efficient

[JumperCable]

It's solar powered. No need to pay any electric bills. Maintenance & care is cheap dirt.
http://pws.byu.edu/tree_tour/images/tree116small.jpg [byu.edu]

Reference point to CO2 emissions

[Hays]

Assuming that 1 tonne = 1000kg, this machine requires approximately 1 kilowatt hour of electricity to remove 10kg of Carbon Dioxide from the atmosphere. How efficient is this?

From http://www.glumac.com/section.asp?catid=140&subid=152&pageid=564 [glumac.com]

"For home energy use, carbon dioxide emissions vary widely from state-to-state and from day-to-day. The national average is about 1.3 pounds of carbon dioxide for every kilowatt-hour of electricity used in your home."

Not bad. If it really works, you can redirect 10 to 15% of your electricity to achieve Carbon neutrality.

I have seen a number of proposals before...

[Chrisq]

I have seen a number of proposals before that make the very basic mistake of using a material to absorb C02 that gives of C02 during manufacturer. Until I see details I will take this with a pinch of salt.

If I had a penny every time someone says "just absorb it all with lime" I would be able to afford a chocolate bar. Besides which, looking at emissions per kw/h [npcil.nic.in] you had better not use coal or oil to power this, and even with Gas produced electricity the benefit is marginal.

Re:it this

[compro01]

Only a lot more efficient. An average tree will use roughly 22kg of CO2 per year. These things are estimated to remove 20 tonnes per year per square metre, so it's in excess of 1000 times more effective. Even after you factor in the CO2 produced to provide the power needed for these things, you're still likely coming out way ahead.

Re:Natural device?

[citizen_senior]

Just wonder how much do we have to wait for a fart capture device (cow farts are actually a major source of trouble)

This has already been done in Holland - no waiting required, therefor - a university study group has work in progress on the subject of cow farts. There are groups of cows standing around with cylinders strapped to their backs in order to (forgive the word) fuel this study. Saw it on /.

Re:Storage Issue

[Anonymous Coward]

Simple enough. Just bubble it up through the ocean.

The ocean is a natural "Carbon sink"-- EG, the minerals (salts) dissolved in the ocean form carbonate mineral complexes when they are exposed to dissolved CO2. This is how all that loverly limestone forms on the bottom of the ocean.

Places with access to "very very deep" ocean trenches are the ideal locations for CO2 sequestering facilities, since the CO2 can be pumped underneath several kilometers of ocean water, and pushed through a bubbler. Most of the CO2 will become dissolved into the ocean water, and precipitate out as limestone and related minerals, and lie harmlessly on the ocean floor.

Re:Natural Gas Processing Plants?

[rukcus]

Energy generation can't be measured in total emissions, but rather by emissions per unit energy produced.

Coal: 1160 g of CO2/kWh
Gas: 400 g of CO2/kWh
PV Solar: 120 g of CO2/kWh (manufacturing)
Nuclear: 55 g of CO2/kWh
Biomass: -4 kg of CO2/kWh

Of course, nuclear has its own special disposal requirements, but it is less polluting in terms of green house gases.

Source: Wiertzstraat, Wise, Coming Clean: How Clean Is Nuclear Energy? Stichting GroenLinks in EU; Brussels, Belgium. Oct 2000.

Re:Natural Gas Processing Plants?

[Viol8]

When you burn gas you get less CO2 for the same energy output than you do from coal because part of the reaction is reacting the hydrogen in the gas with oxygen which produces water so gas plants arn't quite so bad for the enviroment.

CH4 + 2O2 -> CO2 + 2H20

Coal however is almost 100% carbon (apart from some minor impurities).

Re:Storage Issue

[logicnazi]

Hmm, but while you are at it you will hugely acidify the ocean. The chemicals that react with the CO2 only enter the ocean so fast.

The deep ocean trenches may be deep enough to simply liquefy the CO2 so it simply pools on the bottom. This may be more promising. Still not as good as geological storage, however.

Cow Farts... wrong end!

[Enter the Shoggoth]

Actually, it's a common misconception that "cow emissions" are from cow's farting, it's actually the way a ruminant will burp during the processing of a cud that produces large volumes of methane (which is of course more troubling than CO2 emissions)

They won't be making a pile of cash out of trees.

Can't resist:

1) Identify a possible source of trouble 2) Invent a fix, no matter how convoluted it is 3) Patent it and market it 4) Profit

Just wonder how much do we have to wait for a fart capture device (cow farts are actually a major source of trouble)

Re:Storage Issue

[Half-pint HAL]

Apart from the surface, the sea has a pretty stable 2 degree (Celsius) temperature, thanks to the inversion point of water. (Ice floats, but ice always forms on the surface -- it doesn't form at the bottom then float up. Water below 2 degrees is less dense than water above 2, so there's this funky convection thing going on that stops the bottom of the sea freezing.

As for pressure, we're talking about very very deep down in the sea, where a human would be pancakified very very quickly.

In these conditions, CO2 will liquify, if the volume is too great for the surrounding water to dissolve.

HAL.

Re:Natural device?

[Markspark]

The scrubber uses Sodiumhydroxide and Calciumhydroxide that are circulated and regenerated in the process. The power demand comes from separating the CO2 from the CaCO3 back into Ca(OH)2.
But you are correct in the fact that this would require maintenance, since there's no such thing as maintenance free pumps.
However i still feel if this could be a good solution, if it's cost and energy efficient, and being financed by carbon-taxing, and last but not least, F/OSH (free/opensource hardware).

Some points to consider

[Ambitwistor]

First, this isn't a new idea. Artificial air capture of CO2 has been proposed for some time; a noted proponent of this idea is Klaus Lackner [columbia.edu]. I don't think this new group has made a huge breakthrough in the technology. The basic problem is that it's (a) expensive, and (b) you have to put the carbon somewhere.

As for (a), it's currently cheaper to just capture the CO2 at large point sources like coal plants. On the other hand, that only gets some of the emissions. While coal plants are the most serious source of CO2 right now, adding capture to power plants doesn't capture emissions from cars and other small sources. Still, right now it's easier to just make more fuel efficient cars than try to capture the CO2 they emit.

As for (b), the sequestration problem is shared by any carbon capture technology (air capture or not). The main solutions are to pump it into geological formations in land or under the sea, or to convert it to solid form. The latter is relatively expensive and energy intensive. Storing it in the deep ocean is difficult to do on a large scale. On land there are serious limitations on how fast you can pump CO2 into a formation without pressure fractures and leaks, and even then there is a wide variety of formations whose ability to store CO2 varies dramatically. It requires careful siting, monitoring, etc. and you still have to worry about leaks, not to mention all the legal problems with people worrying about the CO2 acidifying the groundwater and leeching out heavy metals.

That being said, I think this technology definitely needs a lot of R&D aimed at it, because though expensive and difficult, it's a fallback position to reduce CO2 levels if energy efficiency and alternative energy measures don't do enough of a job.

Better article available

[IcyHando'Death]

More details from http://www.cbc.ca/technology/story/2008/09/30/carbon.html [www.cbc.ca]

The tower acts as a scrubber, with sodium hydroxide, also known as caustic soda, reacting with air blown into its base. A metal honeycomb system inside the tower slows down the flow of caustic soda, allowing it to efficiently scrub CO2.

While Keith said the technology isn't new -- it's been used since the 1950s in industrial processes that call for carbon dioxide-free air -- he believes his team has surmounted one of the two biggest obstacles to CO2 capture.

For the system to be effective, it must remove more carbon dioxide from the air than it emits as a byproduct of the energy used to run the scrubber. This summer's experiment showed that can be done, said Keith.

He estimates that if the electricity used to run the ambient air scrubber were to come from a coal-fired power plant -- a heavy emitter of CO2 -- he could capture 10 times more CO2 than the coal plant emitted.

Re:Natural device?

[psychosol]

Its True! Trees do remove CO2 from the air! The problem starts, and this is where there is much misunderstanding, with what happens to the carbon in the long term. A tree will absorb a large amount of CO2 during its lifetime, but when after its lifetime, that carbon is released again as the tree decays, or is burned as fuel, etc. The point of CCS is to place the captured carbon in a state that it can be stored for the long term (1000's of years). The problem isn't so much that we are performing processes that release CO2 into the atmosphere, but that the CO2 we are releasing is "new", as in it used to be sequestered underground in a stable form, and now it is being added to our atmosphere. That is why bio-diesel, even if it wasn't less harmful than oil-based diesel, is still an advantage because the CO2 it releases was taken from our atmosphere to begin with, making it close to carbon-neutral. The point is to stop ADDING CO2 to our atmosphere, and start removing and storing it for the long term.

Re:Better article available

[IcyHando'Death]

The tower acts as a scrubber, with sodium hydroxide, also known as caustic soda, reacting with air blown into its base. A metal honeycomb system inside the tower slows down the flow of caustic soda, allowing it to efficiently scrub CO2.

So this answers the question that first occurred to me: in what form is the CO2 stored? For the non-chemists:

CO2 + NaOH ==> NaHCO3 (Sodium BiCarbonate, or baking soda)

NaHCO3 + NaOH ==> H2O + Na2CO3 (Sodium Carbonate, or washing soda)

Look out Arm & Hammer, there's stiff competition on the horizon.

Re:Natural device?

[WalksOnDirt]

If we're serious about reducing the carbon dioxide level by growing trees, we'll have to cut them down and store the wood somewhere where it won't decay. We will also have to replenish the trace elements taken from the soil by those trees so we can grow more. This could work to slowly remove the excess carbon dioxide we've released, but I don't think it would be feasible to keep up with our current rate of emissions.

Re:Natural device?

[Merls the Sneaky]

Actually methane from bovines is expelled in the form of burps, very little methane is farted out.

Re:Natural device?

[blueg3]

They don't respirate as much CO2 as they take up. The carbon from the difference is used to build more tree.