Turning CO2 to Stone | Hacker News Reader

Turning CO2 to Stone

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244 pointsdevinp164 comments

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.

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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.

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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

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.

Edit: this should say $1720 per year.

> when trees die they release CO2

is that really true? If a tree died, i would assume the carbon is either buried, or otherwise remain solid, unless it's burnt.

Some of it is retained in the decayed remains (eventually soil) but much is released in the decay process.

It's worth noting that the decay process takes about as long as the growth process for some trees. For example, a Douglas Fir might spend 600 years alive, and then be a Nurse Log for another 600 --- see http://www2.kuow.org/program.php?id=26100

The CO2 is released when (and if) the tree rots.

Sure, but before then it's stored. And if trees are constantly creating new biomass, you've perpetually buffered an amount of carbon equal to (annual production x time variable). The first variable is limited by the thermodynamics of sunlight, so do what you can to approach that limit. Then the main target of innovation becomes, what forest management techniques can maximize that time variable?

By default about half of a tree's absorbed carbon is injected into the ground to build soil, as root mass and root exudates. Plus trees drop mulch -- mainly leaves. Soil carbon is only released when the soil is destroyed or eroded away. So... don't do that. :)

Dead plant matter used to become coal. Dead plant matter today decomposes:

"Based on a genetic analysis of mushroom fungi, it was proposed that large quantities of wood were buried during [the Carboniferous] period because animals and decomposing bacteria had not yet evolved enzymes that could effectively digest the resistant phenolic lignin polymers and waxy suberin polymers. They suggest that fungi that could break those substances down effectively only became dominant towards the end of the period, making subsequent coal formation much rarer."

https://en.m.wikipedia.org/wiki/Carboniferous See Rocks and Coal

Imagining a forest where dead trees never decompose is quite a mindbender. Certainly a better explanation for the presence of fossil fuels though than just a handwavey mention of geological timeframes.

That depends on how the tree decays. There is a lot of coal near the surface of the western US because prairie grass burned yearly in every dry month (winter when it was too cold to grow - they may still be as much rain/snow!). This yearly burning didn't get warm enough to burn all the carbon and so the rest got deposited as charcoal.

Moral of the story: you should start regular forest/grass fires to turn the stored carbon into charcoal. A biologist can give you a number of other reasons why this is good for the forest as well: common knowledge about forest fires is almost completely false.

This is reverse process of digging coal and sucking oil out of the earth. The problem is that we are now releasing it several orders of magnitude faster than it was put down. The Carboniferous period was a 60,000,000 years long and we will use them in much less than 600 years.

This is something that isn't often mentioned, but from what I understand this is actually kind of a one time deal with fossil fuels. I was under the assumption that the Earth is not likely to have another carboniferous period.

The implication being that we have one good shot at solving civilisation. It just gets more difficult when we start to run out of fossil fuels.

One of the reasons we don't see anything going on out there when we look up could very well be that most civilisations never properly make it off their planets.

Can anyone else comment on this that might have better information than me?

I think for this era, fungi and other consumers of decaying matter could not break down the cellulose walls of plant matter. Since then they did. It is interesting to imagine a species gaining sentience on a planet where there was no coal or oil to power from a wood-burning society of iron to steel and plastics.

I believe it was the lignin specifically which wouldn't decay in the Carboniferous period, leading to most of the fossil fuels around.

I don't think that fossil fuel is the only way to bootstrap up to a high-energy, high-complexity civilization. Hydroelectric generation also yields the sort of dependable, concentrated energy source you need for industrial development, and it was first built with 19th century technology. The necessary 19th century precursor technologies (steel, concrete, wire...) could be manufactured with wood instead of coal. Reservoir-backed hydroelectric dams can also serve, effectively, as a giant battery when you start trying to introduce more abundant but less steady energy sources like wind and solar.

The global potential of energy from hydroelectricity is only a small fraction of our current fossil-based consumption, though. And while wind and solar have potential resources far past fossil power, they can't expand as fast as fossils did historically. So the Fermi Paradox aspect might be that civilizations without fossils and without the self-control to limit reproduction are hobbled by cycles of Malthusian collapse. Or perhaps space-capable civilizations that didn't fall into the Malthusian boom-bust trap while still confined to one planet also don't go crazy with growth once they escape their gravity well, so they're out there but not leaving evidence dramatic enough to be seen by our current telescopes.

You can't really mine for high tech materials without fossil fuels. Hydroelectric won't help when what you need is to extract ore from a mountain.

Electrically driven mining equipment:

http://www.hitachiconstruction.com/about/media-press-release...

http://www.oemoffhighway.com/article/11224086/electrificatio...

If you just mean that it's impractical to build the electrical grid out to a remote mining site, that's true. In the present day remote mining sites typically use diesel fueled generators, now being supplemented with photovoltaic arrays in sunny regions. If you imagine a world with approximately-1940-level technology (so PV is not yet an option) and no fossil fuel, then you'd need to use something like biodiesel or ethanol instead of fossil-derived diesel.

> If you just mean that it's impractical to build the electrical grid out to a remote mining site

Yes, that was the general issue. We do a lot of mining in remote sites that don't have hydro power or any realistic way to get it there. You could use biofuels, but it's hard to imagine bootstrapping a technical society to the point that that becomes feasible without prior use of fossil fuels.

If you have a suitable river not too far away you actually can mine using hydromechanical power. [1] Turning it into electricity loses a lot, but transmission is of course easier

[1] http://www.lowtechmagazine.com/2013/01/mechanical-transmissi...

I do think it's an important idea that fossil fuels should be seen as a stepping stone. They're not useful forever, but using them for too long is bad for all of us, and not being able to use them without a comparable alternative is an equally awful situation.

> I was under the assumption that the Earth is not likely to have another carboniferous period.

Well, we are busy recycling that one. All that carbon in the atmosphere will likely eventually precipitate out. On a geological timescale oil is renewable; it's simply that humans don't live that long. I suppose the cockroach civilization 60 megayears hence will be able to power their vehicles that way.

Or, you could be one of the few who believes the abiotic theory of oil production. I'm not one of them!

A sibling comment points out that back in the carboniferous period, no organisms had enzymes to break down wood. Nowadays, dead wood rots, releasing co2 back into the atmosphere.

This reminds me of earthquakes that in retrospect might be caused by oil drilling, just to name one example.

> 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.

You misunderstand the purpose of trees. They're basically solar powered, organic carbon sequestration devices that happen to run for free. If we ever run out of space to plant trees, we can just cut some down, reduce it down to charcoal and bury it back into the ground which conveniently leaves a readily accessible fossil fuel source for our ancestors in the case of civilizational collapse.

But we're still a long way away from running out of room to plant trees. We're still desperately trying to plant enough trees to stop the encroaching of the Sahara and there's vague, futuristic plans to try and turn the entire Sahara into a forest. Similarly, China is desperately planting trees to stop the encroachment of the Gobi.

Great perspective. I wasn't aware of the Gobi problem either

Reducing trees to charcoal is not cost effective. It releases a ton of carbon dioxide by itself anyway. But it also doesn't make sense that we would plant trees, turn them into charcoal, and then bury that. This is insanely expensive and by the time you've got charcoal, you might as well burn that, too, rather than burying it and then digging up more coal to burn.

The whole reason we had the second stage of the Industrial Revolution is that if you use trees instead of mining then you're limited in energy by the acreage you can devote to trees and that goes down with extra farming as the population increases. To simplify horribly that's why the Ming iron industry with it's chain suspension bridges and so forth collapsed.

If you're removing carbon from the air by burying trees then you'll only be able to sustain the energy intensity of civilization in the Britain of 1800, plus what we can get with renewables. What this new form of capture gives us is the ability to get rid of excess carbon without using huge amounts of arable land to do it.

I mean, we have nukes / nuclear power plants.

There are plenty of high-power ways to make energy without carbon. The question is if enough of the population can accept it.

> That's why we can't "just plant trees": we'd have to be continuously planting new trees.

Yes, that's the point. Plant trees, cut them down when mature and plant new ones. Use the harvested trees to make cross laminated timber and other engineered wood products and use these to replace concrete and steel (which also release CO2 during production). As long as the timber doesn't burn or rot the carbon is stored permanently.

Too for bad that for people in some poorer contries $478 is like many times their yearly income. But then again, their carbon footprint is most likely negligible.

Why not just let nature do it's job? If too much CO2 will kill us, then it's a self regulating system. It happened before with the Azolla event. You get fewer humans, more plants, everything else gets a chance to die off or recover, maybe a new species takes over.

Why bother with carbon sequestration?

Because people don't want to die in the ensuing conflicts over limited resources that climate change is going to bring? Because shrugging one's shoulders at the thought of widespread environmental collapse, starving populations, and the breakdown of ten thousand years of civilization is a horrible thought? Because as the droughts and famines kick in, the people that suffer the most and the most immediately for the first dozen years will be the poor and those in underdeveloped countries, while Silicon Valley programmers sip their Soylent and write comments on Hacker News like this one?

Jesus, grow some empathy.

If the world's population continues to grow exponentially it's going to happen anyway with or without expensive carbon sequestration and silly offset schemes that never work.

Rather than store carbon in solid form, which in fact plants (rainforest and such) already do anyway without the unecessary expense, why not close coal fired power stations and build nuclear? They're safer and the waste is negligible compared to coal and can be further reduced (breeder reactors, thorium cycle etc.). Burning coal also throws heavy metals (Mercury and Arsenic to name a few) and SO2/SO3 into the air. Carbon dioxide is the least of coal's problems because it can be fixed by plants or turn into bricks with additional expense.

Trees aren't a one-time deal.

They will just release their carbon content back when they are burned or transformed in any other way that only the mineral content is left. Otherwise, paper still contains carbon. Coal (buried, not burned) contains carbon. Furniture, houses, anything you make with wood will be a way of storing carbon.

You just also need to supply water and solar light. They will grow. Simple and efficient.

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.

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...

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?

I thought algae was far more efficient than plants?

It is, but where would you get the nutrients needed to grow the algae at a scale needed to offset global climate change?

How about (farm) waste water runoff?

This has been suggested before. Scale is still hard. I read an article in the UC Davis algae magazine (http://www.algaeindustrymagazine.com/department/education/we...) a while ago that talked about flooding a fairly large acre (hectare) parcel with water, growing a layer of algae on it, then burying the algae. (process flood, algae mat grows, drain/evaporate, and plow it all under, then repeat.) The algae decomposition process releases methane (worse than CO2).

> The algae decomposition process releases methane (worse than CO2).

Under what conditions does this happen?

only if we cannot capture methane. If we can capture it, we can run it through an engine and get the energy back. Most landfills are already doing this: it adds some extra profit to the bottom line.

I have no idea if this stores any carbon anymore though.

There is research being done on iron seeding/fertilization of barren ocean waters [0]. In such places, iron is the limiting factor for algae growth.

[0] https://en.wikipedia.org/wiki/Iron_fertilization

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.

Biochar is a possible method to permanently store the CO2 captured from plant matter.

Playing devil's advocate here, water vapor is an incredibly powerful greenhouse gas, even more so than CO2.

I was hoping that someone would mention biochar. Heating your house using the leftover heat from the process of creating biochar could be carbon negative.

I agree there's potential in its use, but what I'm afraid of is 1) the high nutrient requirements needed to grow the biochar at a scale useful to offset global warming, and 2) Biochar is basically coal, which could be burned and converted into CO2 again.

Bury it back. We seem to have huge cavities from used-up coal mines. We could refill them.

I have a new answer for the Fermi paradox. Any sufficiently advanced civilization will develop an extreme "leave no trace" view for ecological reasons.

They refill coal mines, plant trees where there were once cities, and silence radio emissions so that everything appears to be in its "natural" state.

"Any sufficiently advanced civilization is indistinguishable from nature."

Love it!

>the high nutrient requirements needed to grow the biochar

We seem to have forgotten that natural forests are incredibly productive, and don't need artificial fertilizer. So we have a proof-of-concept. How do they do it, and how can we emulate those processes?

Spoiler alert: soil (along with the root action of plants) is essentially a flat biological nanomachine that breaks down solid rock and fixes nitrogen, manufacturing fertilizer in-situ. https://www.youtube.com/watch?v=x2H60ritjag

Of course the logical way to do this is not to create some vast new land use category ("carbon forests" or similar), but to transition our largest current land use category -- agriculture -- from a carbon-releasing to a carbon-sequestering mode. It also helps to increase biomass per hectare in suburbs, by transitioning our current low-carbon-density lawns over to a biome that buffers substantial amounts of carbon.

This is the fundamental insight behind Permaculture btw, which has been working on figuring out exactly what this looks like. It's a hard problem yes, but one with existential importance for humanity.

>Biochar is basically coal, which could be burned and converted into CO2 again.

...so don't do that. :) It's it obvious that burning coal also needs to stop for effective climate mitigation?

In this application, density matters. Biochar is extremely low density, and high in surface area, which makes it an ideal soil amendment which buffers rainwater and provides microbial habitat (not to mention raw carbon for building into soil biomass). By contrast actual coal is nearly worthless in this application.

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?

In most soils the carbon is eventually released by the decay process (through decompositor organisms), though some generally stays sequestered (witness terra preta for instance). Some soils like peats and taiga are strong sinks as they prevent complete decay of organic material, and thus release of the carbon (until they're burned away).

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.

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.

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).

Yes plants die. But don't they also multiply automatically? Doesn't that address the issue?

Sure, but space is the limited resource over which they compete. Smaller plants that can't draw enough resources die or succumb to pests. It's much like animals that have a large number of offspring given their high mortality rate.

Wood can be preserved for centuries, and be very useful as a construction material during that time.

Or you can sink it in the Baltic, where nothing consumes it.

>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

Is it? Let's do the math.

Absorbing the 350 teratonnes of human emitted carbon[1] over the 8.4 billion hectares of Earth's non-tundra / non-desert land surface area[2] works out to... 42 tonnes per hectare. If we can green deserts[3] that drops to 30 tonnes.

That's 30-40 trees per hectare, at 1 tonne per tree.[4] Or 3 kg per square meter of soil carbon, the equivalent of 25-35 cm of topsoil. More likely some combination of the two. Soil carbon is stored up to 40 meters down by deep rooted plants.[5]

Most of our land management is via agriculture, so agriculture seems to be the only lever long enough to make a dent. Practically this implies transitioning from soil destroying tillage to soil building cover crops, long-distance imported fertilizer to in-situ fertility produced by soil organisms, and ecologically unstable monocultures to resiliant polyculture, agroforestry, and rotational grazing systems.

The "gotcha" question is not whether we can replace our existing agriculture with these systems. The question is whether we can replace our existing agriculture with itself. Any unsustainable system is, by definition, not a viable replacement for itself.

[1] http://petrolog.typepad.com/climate_change/2010/01/cumulativ....

[2] http://cnx.org/contents/TWFXbERo@1/The-main-biomes

[3] https://www.youtube.com/watch?v=2xcZS7arcgk

[4] http://cabiblog.typepad.com/hand_picked/2011/06/ever-wondere....

[5] http://www.soilquality.org.au/factsheets/organic-carbon

Note that big farmers have already replaced "soil destroying tillage" with "soil building cover crops". Farm news is full of stories about early adopters 10 years ago bragging about how they are now building soil organic matter with a corresponding reduced need for fertilizer. The big farmers recognize the impact this has on the bottom line. Your mid sized farmers see that extra $10/acre in fertilizer as a cost of business and don't realize they could reduce it.

Unfortunately "long-distance imported fertilizer to in-situ fertility produced by soil organisms" cannot work if food is exported off of the farm. Every gram of food taken off the farm includes some micro-nutrients - various minerals that are required for life that have been removed from the soil and taken elsewhere.

Agreed, we're making a lot of progress on this front!

>Unfortunately "long-distance imported fertilizer to in-situ fertility produced by soil organisms" cannot work if food is exported off of the farm.

It's not like there's a shortage of rocks (where soil bacteria and deep rooted plants harvest and dissolve micronutrients) or air (the source of carbon, as well as nitrogen fixed by rhizobium bacteria in root nodules). Soil tests only look at dissolved nutrients, not those yet to be released from the minerals in rock, which range in size from bedrock to clay. This is detailed in the video I linked.

But it certainly helps if you recycle human waste into fertilizer, rather than just releasing those nutrients into waterways (and ultimately, the ocean) or landfills. The key is to close the fertility loop while also interrupting the fecal-oral route. Thermophilic composting or biogas digesters can do this on a small scale, and systems like those used by Milorganite can do this on a city scale.

Plants don't usually store CO2 long term. You have to do something with them after they grow, or else they decompose and put the CO2 right back into the air.

You mean like eat them?

Cutting them will indirectly release the carbon. Making plants into building materials or cabinetry keeps the carbon locked.

Though even cutting it to firewood has zero sum long-term CO2 balance as long as the forest itself sustains.

s/cutting/eating/ ?

No, eating a plant turns it into CO2. Our / animals' bodies burn the sugars (which were the store of C) into co2 and energy, using the original o2 produced by the plant to convert that co2 into those sugars.

It's more meaningful to reason about co2 storage in terms of area dedicated to plants, than the plants themselves.

> Plants don't usually store CO2 long term.

That's not true, a stable mature forest is a long-term carbon store, the release from decomposition being offset by capture by new growth.

And depending on the underlying soils it may be a net sink until it's clear cut and burned away (e.g. peat swamps as in south-east asian islands).

The point is that a stable forest neither absorbs nor emits net carbon, so if we want to reduce/reverse the rate at which carbon in the atmosphere is growing we need an ongoing net carbon sink. Solid C02 storage can potentially provide this.

> The point is that a stable fotest neither absorbs nor emits net carbon so if we want to reduce/reverse the rate at which carbon in the atmosphere is growing we need an ongoing net carbon sink. Solid C02 storage can potentially provide this.

Growing forests are carbon sinks, until the forest stops growing (and it becomes a carbon store)...

Yes of course, but unlike solid storage, there isn't nearly enough feasible areas to grow forest for a long-term solution.

I would (non sarcastically) like to see the numbers behind that.

Human carbon emissions are currently about 10 billion tons annually (10 Gt/yr), which equates to about 40 Gt/yr of C02.

http://www.wri.org/blog/2013/11/carbon-dioxide-emissions-fos...

Total carbon stored worldwide in biomass, dead wood, and soil is about 640 Gt.

ftp://ftp.fao.org/docrep/fao/010/i0105e/i0105e04.pdf

Of the 550 Gt of carbon humans induced into the atmosphere since 1870, 390 Gt was emitted directly (through burning, cement production, etc), and only 160 Gt was through deforestation and other land use change.

I think the statement you replied to was referring to each individual plant: the forest can capture carbon for thousands of years potentially, but each tree captures carbon for not much more than its lifetime.

> I think the statement you replied to was referring to each individual plant

That's a nonsensical argument and quite literally missing the forest for the tree.

Peat is a great long-term storage for atmospheric carbon [1].

[1] http://www.ipcc.ie/a-to-z-peatlands/peatland-action-plan/cli...

We pull almost all of the CO2 we burn from coal and oil, which were basically underground carbon reserves. To replace all of that CO2 with plant matter would take an immense amount of nutrients, which have to come from somewhere. Then there's the chance that the plant matter will turn to coal or oil again, meaning it may be used again. By turning the CO2 directly into carbonate, you both remove the need for nutrients and turn the CO2 into a form that is both incredibly stable and not useful for any energy purposes, lessening the chance that it will make its way back into the atmosphere.

Exactly. We have pulled an unnatural amount of "usable carbon" to the surface, which, even if it becomes a part of a natural, stable, cycle, will leave us with a higher net amount of CO2 in the atmosphere. We can only go back to "natural" CO2 levels through unnatural means, unless we are willing to measure time on a geological time scale (the millions of years it will take to replace oil reserves from the swamps of today). So until then, we would still be dealing with an acidic ocean and a greenhouse atmosphere.

>We can only go back to "natural" CO2 levels through unnatural means

Ok, but let's be careful not to exclude the middle here. "We got here by mining (an industrial activity), therefore we can't use plants in any part of a carbon sequestration chain (even one that also involves industrial activity)." Trying to use this argument as a blanket ban on plants becomes little more than an appeal to sympathetic magic.

The only thing that matters is how much CO2 a technique can buffer (annual production x time constant), not whether or not it uses plants at any stage. Plants already have enormous annual production, but for economic/thermodynamic reasons it's hard for purely factory-based techniques to achieve sufficient scale. It becomes a money sink both up-front and operationally, respectively because A) factories are expensive, and B) hard thermodynamic constraints mean that it's at a fundamental competitive disadvantage compared to any typical [reminder: energy consuming] factory.

> therefore we can't use plants in any part of a carbon sequestration chain (even one that also involves industrial activity)

Not sure where your logic is coming from here. I am not saying we shouldn't use plants, but I am saying that even if we let forests retake "all the land," the stable CO2 level would be a bit higher than pre-industrialization, and it would stay that way for a long time until dead plant matter returned significant amounts of carbon to the deeper parts of the crust.

Therefore, using other methods like the one in the article are necessary if we want to reduce CO2 levels.

>let forests retake "all the land,"

I agree, a hands-off approach is insufficient. We would need to actively manage those forests (which is just as unnatural an activity btw), using intelligent design to improve upon the carbon density possible solely from blind natural processes.

Big industrial thermodynamic sinks don't scale (and imo never will), simply because they can't economically compete with conventional energy consuming factories. An approach is needed that sequesters carbon while also producing sufficiently valuable goods to society (ie probably not rocks). Food is one possibility, and can avoid carbon futility since in perennial systems the annual food yield is a small percentage of the total carbon stored in the biome.

Plant nutrients are minerals, primarily nitrogen, potassium and phosphorus, in the base form of inorganic compounds or salts. When a plant dies it decomposes and the minerals are released and "recycled". Certainly that's how fossil carbon got to be stored in the first place (by growth of plants) so obviously the availability of nutrients in soils was naturally adequate to support the deposition of carbon.

Carbonates are among the most common minerals on earth, particularly as calcium carbonate in its many forms. Calcium carbonate is slightly soluble in water and subject to degradation in acidic environments. While hardly an impervious carbon dioxide store, that's a benefit in that its easy degradation makes it an extremely useful mineral supporting essential infrastructure industries.

IOW sequestering carbon as carbonates doesn't imply the CO2 is inaccessible but simply not reduced to an elemental or hydrocarbon form readily usable as an energy source. It's a trade-off between storage in an easier/quicker non-energy form or a protracted/difficult-to-implement energy-source form. Worth considering that in geological time the carbonate vs. carbon storage pools will probably "even out" since both are clearly mutable.

Reforestation is good in regions that used to have forests. But using rocks might also work in ardi regions where freshwater is a limited resource (I assume they can just use salt water to pump CO2 into the rocks).

And you can't just plant forests everywhere, for example china experiences issues with its Green Wall, where the trees soak up so much water that it causes the ground water level to fall.

For $15/US resident/year (on average), you could sequester all the carbon you produce that year by having 150 trees planted in return for your donation: http://shindyapin.tumblr.com/post/141034501197/climate-chang...

REVISION: If true, seems like it would feasible for the US, but unclear how regions like Africa & Asian would do the same. Any ideas?

Below is the original comment with correction for accounting error.

_________

$15 per person per US person[2] per year does not sound like a lot, but in sum per year it's a massive amount of money; amount would be $4,847,228,805.

For example, per person using the 2014 net collections[1] of the US's net tax collections divided by the population estimate for July 2016[2], the US revenue per person is $8,000.

[1] ($2,690,755,432) https://www.irs.gov/uac/soi-tax-stats-collections-and-refund...

[2] (323,148,587) http://www.census.gov/popclock/

On the spreadsheet, money amounts are in thousands of dollars.

The US tax charts are reported in thousands, so 2.6 trillion / 323 million = 8k per person, not 8

Thanks, missed the "Money amounts are in thousands of dollars" - corrected the comment above.

Your first link, the numbers are in thousands of dollars so the correct amount is $2,690,755,432,000 nearly 3 trillion dollars.

Thanks, corrected the error.

What do taxes have to do with it? What I'm saying in my blog post is if you want to do something about your personal CO2 emissions and you live in the US, you could donate $15/year to sequester all of them (if you don't live in the US, you would probably need to donate less than $15 to sequester all your CO2 for that year, but you would have to do the calculation yourself).

Edited my comment to reflect this accounting error, revisit the comment to see the correction and related revision.

At the point you're spending billions in sum in a country for a reoccurring & necessary theoricially non-profit service, it would make more sense to do this via the government; yes, I get it's not a requirement, assumes government is functions efficiently, etc.

It might theoretically make more sense to do it via the government, but you can do this right now without waiting for the government.

If that's all it would cost, I would gladly donate $45. $15 for myself and $30 for my parents.

Agree, in the context of the annual budget of the US, seems like this is possible at scale, but feels like this is too simple of an answer; looking into it.

This is the second year I've been donating $100 for my family of six, and a bit more on top of that. (Sorry if this comes off as bragging; my intent is to show that I am putting my money where my mouth is.)

Just realized your username, checked site for updates, and posted the most recent update here, "AutoMicroFarm: My YC Results, AutoMicroFarm Product Development, Moving Forward"

https://news.ycombinator.com/item?id=13457660

Thanks for posting an update - if the titles not right, just post a comment and I'll update it.

Thanks saycheese! I posted that blog post to HN myself a few days ago, but it did not get any traction. :)

Please do research into whatever organization you choose to use.

Some of the carbon offset organizations that plant trees are having a hard time finding people and land to do the work, since cash crop trees tend not to be good carbon collector/stores, poor farmers tend to forego the pay-for-trees to be able to grow cash crops.

I don't know the specific organizations, but I have heard that this can be a complication issue.

Donating to smaller charities tends to go to more specific projects, like these:

https://www.cooleffect.org

https://www.coolearth.org

https://carbonfund.org/projects/

http://www.edenprojects.org

It'd be great if any of these had published progress reports (not to say they don't but I haven't read them). Seems like you could fake one of these pretty easily if you tried.

It doesn't sequester the carbon for very long, though --- the carbon lifecycle of a tree is, what, decades? It consumes carbon when it grows, and then it releases it again when it rots. So it's not really a long term solution.

Its not either or at this point, you need both (as many as possible) solutions. In some regard CO2 storage solutions are better because you can make use of lower priced real estate like ocean floor vs growing plants and forests which take away real estate that can be used for human habitation and agriculture. Also CO2 storage is more stable in time. Like 100 years from now, people might just choose to cut down the forests and just release all that stored carbon back.

We burn oil to produce cheap energy and we get CO2 as a byproduct.

If you want to reverse the process you need some energy, so what would be the point of burning the oil in the first place?

The energy could be from wind, solar -- in fact it might be an ideal use case for those sources if the process can be done intermittently, i.e. whenever the wind is blowing or the sun is shining.

Or you could envision large carbon sequestration plants powered by on-site nuclear.

> Or you could envision large carbon sequestration plants powered by on-site nuclear.

I'm not sure I understand, you're suuggesting that we

1. Burn oil to produce energy (and CO2 as a byproduct)

2. Use the energy to do X

3. Use non-fossil energy to get rid of the CO2 we created during step 1.

When we could just do:

1. Use non-fossil energy to do X

Am I missing something?

0. There's a lot of carbon in the air and we might want to get rid of it.

Yes, I was unclear. We've presumably got 100+ years of industrial carbon emissions to clean up if we want to get back to "pre industrial" atmospheric carbon. Plus ongoing emissions from transportation even if all electrical power is converted to renewable or nuclear.

Transport.

Fossil fuels are incredibly energy-dense and convenient to transport and work with, while renewables aren't. There's plenty of transport systems that are utterly reliant on fossil fuels and couldn't be converted to renewable energy. Carbon sequestering would allow continued use of these while staying carbon-neutral.

That seems like a very circuitous and inefficient way to avoid electrifying transport. Batteries are hard, but they're not that hard (as Tesla's rapid progress is demonstrating).

Land transportation accounts for the majority of liquid fuel use, and much of that can be replaced by battery power assuming that battery costs continue to drop. I'd guess that battery powered airliners and long distance cargo ships will not become practical. Those and other transport applications particularly demanding of energy density account for a large enough residual of liquid fuel use that it's worth thinking about how to avoid fossil emissions from them. Synthetic liquid fuels made from non-fossil energy sources is one way to do it. (Biofuels are an option too, but plants are a lot less energetically efficient than solar farms, so you need a lot more production area for biofuel than synthetic fuel.)

>I'd guess that battery powered airliners and long distance cargo ships will not become practical.

We shall see. For whatever it's worth, Tesla's CEO disagrees. https://www.youtube.com/watch?v=0871VJfvD1c&t=57s

>I think all transport, with the exception of rockets, will go fully electric.

This is the most recent example, but he's been saying this since at least 2013. Surprisingly, he's also made it clear that he thinks this applies to ships and planes too. http://www.digitaltrends.com/cool-tech/elon-musk-electric-ai...

I do not think batteries will ever get a useful enough energy/weight ratio for airplanes. https://en.wikipedia.org/wiki/Energy_density Not only does jet fuel have a much better energy to weight ratio, but you don't have to carry the weight of your spent fuel. A battery powered airplane needs to get all its fuel to altitude while a fuel powered one has much less mass to get up (and stop when you get to the ground).

Ships probably will see batteries as an asset: they can place them in ideal locations for weight distribution/stability.

I think it's hard, yes. But I also think forever is a long time. ;)

You certainly can't get there by taking an existing aircraft, removing the fuel and replacing it with batteries. It's the same fallacy as the gasoline automakers make with electric cars, and it results in a worse vehicle design. The whole system has to be re-imagined from the ground up to exploit the advantages of electric propulsion.

Several of the design concepts for his proposed supersonic VTOL electric transcontinental commercial jet airplane have already been revealed:

* The plane would fly at high altitude, somewhere around 80,000 ft. Combustion airplanes have a 30-40,000 ft ceiling limited by the need to ingest oxygen. Due to the exponential decay of density with height this dramatically reduces drag, thereby reducing engine power and structural stress. Coincidentally this is also higher than almost all bad weather.

* VTOL is easier since electric motors have a better power:weight ratio than turbine engines. This eliminates constraints due to runway length and width, and means the wing can be more closely optimized for cruising. It also means smaller airports are possible, reducing gate fees.

* The wings also don't need to double as liquid fuel tanks, and don't need to handle different stresses when empty vs full.

* A high mass fraction of batteries compared to combustion aircraft (mid to high 70% range). Energy density at least 400 Wh/kg (which as you point out, is still much lower than kerosene).

* Eliminating the tail section in favor of gimbaling the electric fan, again reducing drag and weight.

* You also get about a 1% drop in weight compared to existing jets due to reduced gravity and centrifugal force.

A good video compilation of quotes is https://www.youtube.com/watch?v=erjdYiwoYAo

Batteries are still a long way from being useful for ships, long-haul trains and trucks, and large aircraft.

If we want to reverse the CO2 we released by burning all these fossil fuels, at some point we'll need to essentially "unburn" them - and yes, that would necessarily involve "paying back" all the energy humanity got from burning these fuels.

We'd only need a large amount of energy if we want to turn it back into a high-energy compound like oil or coal. The method described in the article has CO2 turning into calcium carbonate, which does not need an energy input (in fact, it releases energy in the form of heat)

I've been doing preliminary research on what kind of high-density trees grow reasonably fast in different climates. If the wood has a high enough density it will sink in water without treatment. Wood that has been submerged can take 100s of years to decay. Hence it might be possible to lock away a lot of carbon and give us some breathing room, by repeatedly clear-cutting and reseeding forests and sinking the logs. Even without high-density wood, it might be worth the effort to treat the timber so that it will stay sunken. I did some estimates previously that suggest the amount of land area that would have to be dedicated to this to reduce atmospheric CO2 is not unreasonable.

Why sink when you could dehydrate it in the desert? Rot needs water.

Wonder what that would do to the desert over time. If it could reclaim some desert land it would be wonderful.

Part of the equation is do what makes the most sense locally. So sure, if you are closer to desert, that's the way to go.

If you are close to the desert you probably don't have forests though. Tree need a lot of water, as things get dryer the land transitions to grassland before desert.

Of course mountains are often a factor. There are deserts at the base of forested mountains. The mountain takes all the rain.

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.

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

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.

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).

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.

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.

For a number of reasons that won't happen with existing plants, but the two bigs ones are that the plant economics are based on selling electricity to the grid and the operating cost of a nuclear plant today, makes for very expensive oil and gasoline (an equivalent of $125 - $150 barrel of crude oil prices). However if you built a nuclear plant that was specifically designed for F-T (so for example you used it to bring the F-T reactor up to 1300 degrees) you might be able to get the cost down to something a bit more competitive at the moment. The big advantage of course is that you could build such a plant with a 50 mile (80 km) radius (thus ensuring that even a Chernobyl style disaster would have not have long term effects on anyone outside of the safe zone) build a rail spur or a pipeline to exfiltrate the production.

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.)

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.

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.

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.

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.

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.

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.

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.

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.

There is an entrepreneur I follow on Twitter working on this. Press Release: http://www.orica.com/News---Media/australian-research-pilot-...

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

http://xkcd.com/1732/

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

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.

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).

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.

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.

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.

The optimal way of storing carbon is as coal.

More optimal than diamond?

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...

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...

Hence why graphite is generally more plentiful than diamonds.

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...

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

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

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)

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

Just burn it and sell the electricity and freshwater?

Then it becomes 1 CO2.

http://chemistry.elmhurst.edu/vchembook/511natgascombust.htm...

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

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?

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

https://www.enbridgegas.com/assets/docs/Gas%20Analysis%20Vic...

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...

methane cracking is probably worth mentioning, then you could burn only the H2. The drawback of course that it will produce less energy.

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

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).

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.

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

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

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