
Turning CO2 to Stone - devinp
http://sciencebulletin.org/archives/6839.html
======
owenversteeg
I was curious, so I did the math.

Total worldwide carbon production is 38.2 billion tons per year. Cost to
sequester a ton of carbon is between $30 and $150, depending on who you ask
and how you do it. Let's assume a middle of the road price of $90/ton. That's
$3.438 trillion a year, or about $478 per person. This is roughly equal to the
US yearly federal spending, or 3% of the world GDP.

If you somehow pooled together all the world's billionaires and got them to
contribute their annual income (roughly $600 billion a year, averaging the
past 7 years) to the effort, you could eliminate roughly 20% of carbon
produced in the world every year.

\-------------------------

Suddenly, it becomes crystal clear why finding new sequestration methods is
incredibly important: if you can get the cost from $160 to $10 per ton, then
suddenly all you'd need would be a coalition of half the world's billionaires
to stop the main cause of global warming.

Additionally, it's important that people realize that CO2 production is in
tons of CO2 per year. Tree offsets are a one-time deal, since when trees die
they release CO2, and when new ones are born they absorb that CO2 again. After
they've been planted, forests are generally carbon neutral. That's why we
can't "just plant trees": we'd have to be continuously planting new trees. The
Earth is only 8% arable land, much of which already has stuff on it, or is
undesirable for one reason or another. We'd run out of space pretty fast.
Trees are good for other reasons: preventing climate change (different from
global warming), preserving species diversity, being nice to look at, etc etc.

\-------------------------

Mostly off-topic: when I was looking at estimates of land size, apparently the
amount the US has shrunk from 2007 to 2015 (14,000 km2; went from 9,161,120
km2 to 9,147,420 km2) [0] is roughly equivalent to half the area of the
Netherlands. Wow.

[0]
[http://data.worldbank.org/indicator/AG.LND.TOTL.K2](http://data.worldbank.org/indicator/AG.LND.TOTL.K2)

~~~
semi-extrinsic
You also have to remember the costs of capturing CO2, which is best done at
the points of emission, and transporting the CO2 to the (usually far away)
storage site.

OTOH, the total cost (not just for sequestration) is about $100, maybe a bit
more, in most estimates.

For reference, a gallon of gas produces 20 pounds of CO2, so $100/ton equals
$1/gallon of gasoline. That's roughly what you'd have to increase gasoline
price by to fund CO2 capture, transport and storage. (This neglects that the
capture part is neigh-on impossible.)

For electricity, to compensate for the average US CO2 emissions per kWh (~1.2
lbs/kWh), you'd have to increase the price by about 6 cents per kWh.

To do CCS for both gasoline and electricity consumption, the average US family
would have to pay (order of magnitude) 1000 x $1 + 12000 x $0.06 = $1720. That
would compensate for about half the family's CO2 emissions. The remaining half
is dominated by emissions from the food we eat, the stuff we buy and from
having fun.

~~~
semi-extrinsic
Edit: this should say $1720 per year.

------
philipkglass
The net reaction goes like this: CaSiO3 + CO2 -> CaCO3 + SiO2. Note that the
products, silicon dioxide and calcium carbonate, are thermodynamically stable
solids.

Crucially, the _activation energy_ for the weathering of silicates to
carbonates is low in the presence of water and carbon dioxide. Low enough that
it happens spontaneously in nature on exposed rock surfaces. That means that
the energy inputs required to reduce atmospheric CO2 via silicate weathering
are _much_ lower than a "combustion in reverse" process to turn gaseous CO2
into synthetic coal and bury it.

The other crucial issue is that the _kinetics_ of silicate weathering are
tremendously hindered in nature. A freshly fractured basalt surface weathers
rapidly for a year or two and then develops a cation-depleted micron scale
"rind" that drastically slows the weathering reactions with the rest of the
bulk rock.

One way to accelerate the kinetics of silicate weathering is to use more
concentrated materials, like the Iceland injection process: nearly pure CO2
plus water will react much faster than natural surface waters exposed to
hundreds-of-ppm CO2 in the atmosphere. That works ok if you have a rich stream
of CO2 like directly from a power plant's stacks. It won't work for dealing
with CO2 already emitted to the atmosphere unless you add a complicated and
energetically expensive pre-concentration stage to turn 400 ppm of atmospheric
CO2 into a 950,000 ppm CO2 stream you can inject.

The other way to improve the kinetics of silicate weathering is to generate a
lot more surface area: crush bulk stone into particles 100 microns or finer.
Then there's a lot of fast-reacting extra surface area that can react with CO2
at ambient concentrations. And even the slow weathering to the center of the
particle will take maybe a century rather than multiple millennia. (If a
century sounds unacceptably slow, I would venture that you have not fully
internalized the vast timescales that unaided nature would take to restore the
pre-industrial CO2 equilibrium.)

Putting crushed stone particles in near-shore ocean environments may further
accelerate weathering by ensuring that natural wave action keeps abrading the
rind from particles. Crushed stone rich in magnesium and calcium silicates can
also be applied to acid sulfate soils in tropical agriculture. Raising the pH
of acid soils increases agricultural productivity by preventing low-pH
aluminum toxicity to plants and, unlike sweetening soil with limestone, it
sequesters some carbon at the same time. The crushed stone accelerated
weathering approach can offset all sorts of CO2 emissions: point or
distributed sources, local or distant sources, present or past sources.
Finally, it restores the historical pH balance of the oceans as well as
getting rid of excess radiative forcing from CO2.

The amounts of stone required to offset historical emissions are vast, but any
solution will be vast because the scale of the problem itself is vast. In
terms of scalability, simplicity, energetics, and flexibility, I think that
accelerated silicate weathering is the best shot at long term restoration of
oceanic and atmospheric CO2 concentrations to the pre-industrial baseline.

~~~
wycx
You can see a similar reaction in action when you work with MgO. When
preparing starting materials for high P high T experiments on basaltic liquids
we typically make mechanical mixtures of simple oxides. MgO is the usual
magnesium source, and we always have to calcine the MgO before weighing, as it
always takes on CO2 whilst sitting around in the jar. If you put some freshly
calcined MgO on some weighing paper on a balance, you can sit there and watch
the mass increase as it reacts with CO2 from the air. Alas, too much silica on
earth for periclase rocks...

------
VeejayRampay
It's nice that we're looking to alternative ways to capture and store
atmospheric CO2, but at time it also does look like we're working too hard to
replicate a system that does that already (and has for a long time): plants.

Or does it mean that the time of planting trees and preserving forests is over
now and we have to do it another (most often less efficient) way?

~~~
Daishiman
The problem with plants is that they do not sequester CO2 permanently; plants
grow, die, and decompose, releasing carbon back into the atmosphere. Trees
certainly work as a buffer in the sense that carbon in plants is carbon not in
the atmosphere, but the amount you could hold is tiny in comparison to the
amount that must be sequestered back in order to make a meaningful change in
atmospheric and oceanic CO2 composition.

Nonetheless, plants have important benefits, since they alter the local
climate by changing the albedo and perspirating. Perspiration of plants in
jungles helps to create clouds and regulate humidity, and would help to
counteract some of the negative effects of climate change.

~~~
ced
Isn't soil basically just decomposed organic matter, i.e. a big carbon store?
What fraction of a plant's carbon goes into the soil vs. into the air?

~~~
ph0rque
By burying a plant, you could consciously make that fraction very close to 1.
This is a way to fertilize the soil for future plants, and is called
hugelkultur.

~~~
bunderbunder
Hugelkulture doesn't involve burying the plants very deeply though - I suspect
that it's shallow enough that CO2 that's released during decomposition can
easily make it back to the surface.

Most the CO2 from fossil fuels comes from ancient bogs, where plants were
prevented from decomposing for long enough that they could eventually turn
into materials like coal and petroleum. In essence, they were a result of
taking plant matter _out_ of the biosphere, which is sort of the opposite of
hugelkultur's goal.

~~~
ph0rque
Hugelkultur is intended primarily to act as a long-term (5-20 year)
fertilization and water absorption mechanism, so that other plants planted on
top of the mound grow better.

In that context, you will have a net-positive CO2 absorption (or, a net-
negative CO2 release into the atmosphere).

------
Gravityloss
We have a great method of storing carbon. It is also technologically simple,
very stable, and, would you believe it, completely free! It is called coal. It
was already stored in the ground millions of years ago. We just have to not
dig it up and burn it.

Also related: oil, peat.

~~~
yeukhon
No you don't. Those were the results of millions of years. Don't dig it up?
Okay, find alternate engery source which can support the way we live today. I
am all for reduction (I believe in climate change), but what you said came out
very aggressive and counter productive. So noz

~~~
Gravityloss
It's literally very ineffective to keep burning coal, dilute the CO2 to the
atmosphere and then fantasize about collecting the 400 ppm ambient later.

It would be easier to replace as much coal as possible with other forms of
energy as soon as possible.

~~~
yeukhon
What makes you think people aren't trying hard enough? It's the fact we
haven't come up with an alternative clean source of energy able to sustain the
rate of our current consumption. None of the green energy we know of can do
that right now (be it too costly, or just not enough power generated).

~~~
Gravityloss
It doesn't have to be a 100% solution at first. The CO2 problem is cumulative.
Every ton of coal left unburned is helpful. The earlier those nukes, windmills
or solar panels go up, the more coal they displace.

We just had an article on HN where Wyoming banned renewables.

------
jjawssd
Would be very interesting to see nuclear energy sources harnessed to split
carbon dioxide into oxygen and carbon or generated into liquid fuels.

I can't wait to see nuclear power plants selling oil and gasoline.

~~~
pjc50
I believe the US Navy already have pilot plants for doing this on nuclear-
powered aircraft carriers. It's too expensive for land use but much better
than shipping across potentially hostile waters.

(Gasoline on US bases in Afghanistan ended up costing something more than
$100/USgal, due to being taken overland several thousand miles through
Pakistan under armed escort due to occasional Taliban attack.)

------
teddyg1
Not mentioned in these comments is the actual method they cite in capturing
the solid CO2. The method involves bubbling CO2 through water and hydrogen
sulfide, which is incredibly toxic. Not sure if there's a better way to do it,
but their current process is both economically infeasible and dangerous.

~~~
Dylan16807
I don't think 'incredibly toxic' is the best word for a smell most people are
familiar with.

Industry uses toxic chemicals all the time. It's not a big deal. This is a
chemical that's relatively easy to notice and where prolonged non-acute
exposure doesn't have known harms. It's better than most.

------
chris_va
Just a reminder that the Iceland study result was unexpected, and while it is
great that the media is publicizing the results, it would be nice to get
additional confirmations before getting really excited.

Having said that, I'm still kind of excited. The basalt flood in Eastern
Washington alone is in theory large enough to sequester hundreds of years of
US emissions.

------
stcredzero
The best way to reduce emissions of CO2, is to develop sources of energy that
are more economical than fossil fuels. If we had the huge surpluses of carbon
emissions free energy implied by fusion, we'd be able to slash energy-related
carbon emissions to a small fraction of the current level, while also
drastically reducing the need to extract hydrocarbons as a chemical
feedstocks. Fusion is probably even capable of providing enough energy to
sequester excess carbon, beyond emissions.

~~~
hvidgaard
Fusion energy is not free. The cost of building a reactor alone puts the price
in the same range as fission. But it's safer, and we have an abundance of fuel
for it. So build it to handle base loads, use wind/solar where it makes sense,
and use excess production to some meaningful task.

~~~
stcredzero
_The cost of building a reactor alone puts the price in the same range as
fission. But it 's safer, and we have an abundance of fuel for it._

The 2nd sentence will eventually put it in a lower price range than fission.

~~~
hvidgaard
The fuel cost of a fission planet is less than 15% of TCO, so it's not going
to be much cheaper, if at all.

------
drallison
Scaling up this technique to make it practical is going to be challenging. And
it is not enough to simply compute the quantity of carbon not emitted; the
full energy-life-cycle of the sequestration needs to be computed as well.

------
grizzles
There is an entrepreneur I follow on Twitter working on this. Press Release:
[http://www.orica.com/News---Media/australian-research-
pilot-...](http://www.orica.com/News---Media/australian-research-pilot-plant-
turns-co2-into-potential-green-construction-materials#.WIUS6vGGNhE)

------
batguano
This made me appreciate how much a few degrees C of climate change matter:

[http://xkcd.com/1732/](http://xkcd.com/1732/)

When the world climate was 4.3 degrees Celsius colder, Boston was covered
under a mile-high sheet of ice.

------
pasbesoin
I haven't read this, but do people forget basic chemistry? We burn fossil
fuels because the process is exothermic -- we extract usable energy from it.

Lithification of CO2 (to make up a word?) is, as far as I know, endothermic.
It takes energy to accomplish. On the surface, tending towards counter-
productive. Burn fossil fuels to lithify CO2 from burning fossil fuels. Or
ramp up nuclear, with all its problems, for the same.

Fusion, sure -- but we are not there, yet.

Unless we look at the sun -- solar and wind. (The largest fusion reactor we
are going to have -- up in the sky.)

"Alternative", next-generation, "renewable" energy might allow us to divert
part of its potential excess supply to lithification of CO2. At the
"tailpipe/smokestack" of conventional production, or even, if we can figure
out effective capture, out of the sky.

You want CO2 dealt with, you're going to need to find a way to package it into
a stable solid state.

By the way, we already have one worldwide, extant system for lithification of
CO2. Based upon solar energy. Photosynthesizing flora.

Trouble is, we are outracing its natural counterbalance while simultaneously
reducing and eliminating the flora required for it.

~~~
ComputerGuru
This process of trapping CO2 in stone is very, very different from converting
CO2 to artificial coal and does not require the same magnitudes of energy (or
anywhere near them).

~~~
pasbesoin
Sorry if I wasn't clear. I wasn't referring to trapping CO2. I don't regard it
as long term capture, whereas "stonification" \-- actually making the stuff
part of a mineral we know has long-term persistence -- is.

------
sytelus
On a very off-topic note, I wanted to know how human beings can colonize gas
giants like Jupiter and Saturn assuming they somehow have access to huge
amount of energy. One key problem that would be needed to solve is exactly
this: converting gases like CO2 and methane to solids.

~~~
Eric_WVGG
colonize != terraform

Even if you somehow converted the gasses of Saturn into solids, the mass would
result in a level of gravity that would not be survivable. I don't think
there's any possibility for colonizing gas giants that doesn't involve
something like Bespin or Jetsons floating platforms.

------
scentoni
The optimal way of storing carbon is as coal.

~~~
SixSigma
More optimal than diamond?

~~~
truncheon
Somewhat, yes. It seems that graphite is a somewhat more relaxed state than
carbon's diamond crystal allotrope.

Both burn, and can be vaporized with LOX/acetyline torches:

[http://www.popsci.com/sites/popsci.com/files/styles/medium_1...](http://www.popsci.com/sites/popsci.com/files/styles/medium_1x_/public/import/2013/images/2009/08/diamond3.jpg)

But apparently, over long periods of time, and unless coerced, carbon prefers
to be graphite and so, diamonds can decay as such. [0]

[0]
[https://en.wikipedia.org/wiki/Material_properties_of_diamond...](https://en.wikipedia.org/wiki/Material_properties_of_diamond#Thermal_stability)

Hence why graphite is generally more plentiful than diamonds.

~~~
SixSigma
Coal isn't graphite though.

And you're talking about burning, not storage. Coal produces lots of dust and
debris. I'm sure diamond would produce some dust at volumes.

[https://www.quora.com/What-is-the-difference-between-coal-
an...](https://www.quora.com/What-is-the-difference-between-coal-and-graphite)

Anyway, it's fantasy because I'm fairly confident we're not going to turn CO2
into mountains of diamonds in my lifetime!

------
okonomiyaki3000
Question: once this CO2 has been changed into a solid form, will we be able to
burn the solids to produce energy?

~~~
kmm
The resulting carbonate minerals can't be burned because they are already
completely oxidized, the same way you can't burn water (with oxygen).

Carbonate minerals are a lower energy compound than their reactants, which is
good, because it means the reaction will happen spontaneously without an
energy input from us (which would probably be too large to make it economical)

------
EGreg
What about methane, anyone got stuff for that?? It's much more potent of a
greenhouse gas than CO2.

~~~
mazlix
Just burn it and sell the electricity and freshwater?

Then it becomes 1 CO2.

[http://chemistry.elmhurst.edu/vchembook/511natgascombust.htm...](http://chemistry.elmhurst.edu/vchembook/511natgascombust.html)

~~~
fnj
Plus traces of CO, NOx, carbon particulates, and unburned hydrocarbon.

~~~
pbhjpbhj
Methane is CH4, if you burn in oxygen then you get CO2 (and some CO
potentially as you say) and H2O. Where's the NOx come from?

Can you get particulates burning methane? Long chain hydrocarbons, I can see
how that works; but methane seems like it would disperse too easily, unless
it's liquid/solid methane you're burning or you're doing it in a very low
pressure atmosphere. That's my intuition though, any citations showing
significant particulate yield with methane combustion?

~~~
fnj
Any hydrocarbon fuel burning in atmospheric air produces _some_ NOx,and some
particulate matter. I should also have mentioned SOx, at least considering
that your methane fuel is not going to be chemically pure CH4. Natural gas, in
addition to CH4 as the primary component, contains some ethane and propane,
plus traces of butane, pentane, hexanes, N2, CO2, and sulfur.

I'm not sure what amounts of pollutants one would consider "significant".
Certainly, gas turbines burning methane are comparatively low in pollutants,
but even properly functioning automobile engines are extraordinarily low in
pollutant emission (just for orientation, I don't consider CO2 "pollution").

[http://www.gasturbine.org/images/thegasturbinesolution.pdf](http://www.gasturbine.org/images/thegasturbinesolution.pdf)

[https://www.enbridgegas.com/assets/docs/Gas%20Analysis%20Vic...](https://www.enbridgegas.com/assets/docs/Gas%20Analysis%20Victoria%20Square%20Stn%20No%2050139%20-%20September%202016.pdf)

~~~
pbhjpbhj
Thanks for the reply. I'd guess you're always going to get side combustion of
existing products in the air, you could probably say "methane combustion
produces heavy metals" too in that case as there's a chance that there'll be
an atom of a heavy metal floating around the intake air. But it's needs to be
noted and practical effects considered.

>gas turbines burning methane are comparatively low in pollutants //

Do they ever burn just methane or do they burn natural gas [that's been
somewhat purified]?

I did have a search before posting and found citations claiming natural gas
gave significant particulate reduction, as your second citation mentions, ergo
the question of whether burning methane made any - it seems primarily to be a
factor of burner efficiency, though there's research showing production of
fullerenes and nanotubes that probably feeds in here too.

Looking further I found [1] which gives good info, in particular whilst
gas:oil is 7:2704 in production of particulates by weight that citation notes
that the PM2.5 [small particulates] as opposed to PM10 particulates _may_ be
significantly more damaging due to their penetration further in to the
respitory system.

[1]
[http://www.eia.gov/pub/oil_gas/natural_gas/analysis_publicat...](http://www.eia.gov/pub/oil_gas/natural_gas/analysis_publications/natural_gas_1998_issues_trends/pdf/chapter2.pdf)

------
Jean-Philipe
I heard there's also a way to turn CO2 into wood.

------
sandworm101
Storing co2 under the sea? Imagine what a leaking well will look like: a giant
soda straw injecting c02 directly where it can do the most damage.

Carbon storage may be a stop-gap but, as with "clean coal", is also used as a
pr flag to justify continued fossil fuel expansion. With the price of solar
dropping, that is where we should focus (and fusion).

~~~
philipkglass
The point of this article is that the injected CO2 reacts with the rocks to
create stable solids, so that it _can 't_ leak even if the physical
containment fails after a few years. That is a significant improvement over
e.g. schemes to inject CO2 in depleted oil fields, where physical containment
failure would indeed undo all the benefits of sequestration.

~~~
sandworm101
Except for when the pipe breaks, much like every oil-related accident. Pipes
+ocean +pressure always creates risks.

~~~
_coldfire
Except that we control the flow into the pipe and can turn it off in a minute,
unlike every oil-related accident.

