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posted by martyb on Monday August 20 2018, @10:07AM   Printer-friendly
from the sequestration++ dept.

This Lab-Made Mineral Just Became a Key Candidate For Reducing CO2 in The Atmosphere

Scientists just worked out a way of rapidly producing a mineral capable of storing carbon dioxide (CO2) - giving us a potentially exciting option for dealing with our increasingly overcooked planet. Magnesite, which is a type of magnesium carbonate, forms when magnesium combines with carbonic acid - CO2 dissolved in water. If we can produce this mineral at a massive scale, it could safely store large amounts of carbon dioxide we simply don't need in our planet's atmosphere.

[...] Being able to make the mineral in the lab could be a major step forward in terms of how effective carbon sequestration might eventually be. "Using microspheres means that we were able to speed up magnesite formation by orders of magnitude," says [Ian] Power. "This process takes place at room temperature, meaning that magnesite production is extremely energy efficient."

[...] With a tonne of naturally-occurring magnesite able to capture around half a tonne of CO2, we're going to need a lot of magnesite, and somewhere to put it all as well. As with other carbon capture processes, it's not yet clear whether this will successfully scale up as much as it needs to. That said, these new discoveries mean lab-made magnesite could one day be helpful – it puts the mineral on the table as an option for further investigation.

Abstract.

Related: Negative Emission Strategy: Active Carbon Capture
Carbon Capture From Air Closer to Commercial Viability


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  • (Score: 2) by takyon on Monday August 20 2018, @04:46PM (8 children)

    by takyon (881) <reversethis-{gro ... s} {ta} {noykat}> on Monday August 20 2018, @04:46PM (#723818) Journal

    ^^ Note that you can get it from desalinization, which gets you some other useful products. You don't have to dig it up.

    The money might be worth spending *if* the process does decrease CO2 overall and you put a high value on lowering that number.

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  • (Score: 1, Insightful) by Anonymous Coward on Monday August 20 2018, @05:31PM (4 children)

    by Anonymous Coward on Monday August 20 2018, @05:31PM (#723838)

    ^^ Note that you can get it from desalinization, which gets you some other useful products. You don't have to dig it up.

    Magnesium is present in seawater at concentrations of about one part per thousand. So you can get about one tonne of magnesium from one thousand tonnes of seawater.

    Estimating from standard atomic weights gives that magnesite is about ⅓ magnesium by mass. So to get one tonne of magnesite you could get the required magnesium from about ⅓ kt of seawater.

    TFA says one tonne of magnesite will sequester about half a tonne of CO₂ (assuming you can produce it with zero carbon dioxide emissions). This is consistent with the atomic weight estimates.

    To get enough magnesium from seawater, then, to produce the 8 billion tonnes of magnesite [soylentnews.org] per year required to offset human breathing, you must process about 3 trillion tonnes of seawater per year. That's on the same order of magnitude as the global freshwater water usage by humans.

    So if we were to replace literally all modern human uses of freshwater aquifers and essentially all other natural sources of freshwater with desalination, and do it all with zero carbon emissions, then maybe we'd be processing enough seawater just to produce enough raw material for this carbon sequestering process from seawater to offset human breathing

    • (Score: 2) by takyon on Monday August 20 2018, @06:33PM

      by takyon (881) <reversethis-{gro ... s} {ta} {noykat}> on Monday August 20 2018, @06:33PM (#723862) Journal

      Yeah, might be easier to start injecting sulfur compounds [technologyreview.com] into the upper atmosphere.

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    • (Score: 2) by Zinho on Monday August 20 2018, @06:37PM (2 children)

      by Zinho (759) on Monday August 20 2018, @06:37PM (#723865)

      To get enough magnesium from seawater, then, to produce the 8 billion tonnes of magnesite [soylentnews.org] per year required to offset human breathing, you must process about 3 trillion tonnes of seawater per year. That's on the same order of magnitude as the global freshwater water usage by humans.

      That's good news, then! Our friends at El Reg have done the math, and it already looks favorable economically to replace natural water sources with desalination in places like California [theregister.co.uk] and London. [theregister.co.uk] What's holding us back is the sad fact that the energy used to do so would lead to release of CO2. If replacing our drinking water offsets our CO2 use, then we're into two-birds-one-stone territory.

      Naturally, it would be better to run the desalination from a zero-emission source like solar, wind, hydro, or (please $DIETY, let it be soon) fusion. Of course, once fusion is an option, we're back to fritsd's argument [soylentnews.org] that the CO2 problem is solved at that point anyhow.

      Still, I'm happy that desalination is within an order of magnitude for producing the magnesium we'd need; my first reaction to this article was, "who is going to need all that magnesite?" With the prospect of sourcing the raw material from a process we kinda need anyhow, combined with a market for the waste product as building material, there's hope that the economic loop might close and make this a reality. I've seem much worse proposals for methods to save the earth from CO2.

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      • (Score: 1, Insightful) by Anonymous Coward on Monday August 20 2018, @08:19PM (1 child)

        by Anonymous Coward on Monday August 20 2018, @08:19PM (#723894)

        Our friends at El Reg have done the math, and it already looks favorable economically to replace natural water sources with desalination in places like California [theregister.co.uk]

        El Reg used an 11 trillion US gallon figure (about 40 billion tonnes) from NASA and go with that. The NASA number, if you go to the source, is actually the amount of water required to replenish the aquifers to normal levels (not the actual consumption of the state). However, this figure coincidentally turns out to be pretty close to the yearly freshwater usage of the state [usgs.gov]. They use a 7kWh figure per tonne as the energy required by the reverse osmosis process. So that means it will take about 300 TWh to desalinate that 40 billion tonnes. Over the year that's about 35GW.

        The total electricity generation of the United States in 2017 [eia.gov] was 4000 TWh. About 65% of that was generated by burning fossil fuels, so the nuclear and renewable portion of that is just 1400 TWh.

        So we're talking about about 10% of the entire electrical generation capability of the entire United States, to desalinate the water used by California alone. Or about 50% of the entire country's non-fossil-fuel-burning electrical generation capability, just to desalinate the water used by California alone.

        The biggest nuclear plant in the United States [eia.gov] has 3 reactors and has a peak generation of about 4GW. In principle I suppose we could build ten of these in California and use them to run a massive reverse osmosis capability to desalinate that 40 billion tonnes per year. So it appears possible but I doubt it is economical. I think El Reg's conclusion that it is economical is due to their comparison with the state's total energy consumption figure; which includes non-electrical uses and the lion's share of which is transportation (mostly burning fossil fuels... and also that energy is not really in a form usable for desalination purposes), and the assumption that diverting such a massive amount of electrical energy to desalination will have zero impact on prices.

        And that's just 1% of the 3 trillion tonnes of saltwater needed to extract the 3 billion tonnes of magnesium to produce 8 billion tonnes of magnesite to sequester the 4 billion tonnes of carbon dioxide from humans breathing alone.

        Still, I'm happy that desalination is within an order of magnitude for producing the magnesium we'd need;

        There is a secondary problem. Magnesium is essential for life on Earth. About 70% of the global freshwater usage is in agriculture, and you need to add the magnesium back to the water (you could alternately add it to the soil) after desalination or it's going to eventually kill the crops you irrigate with it. You probably don't need to use all of it, though, as freshwater typically has much lower concentrations than seawater.

        Also, it's unclear to me if the reverse osmosis process normally used for desalination can even be used to extract elemental magnesium from seawater, so a different (perhaps more energy hungry) process might be needed.

        • (Score: 0) by Anonymous Coward on Monday August 20 2018, @09:58PM

          by Anonymous Coward on Monday August 20 2018, @09:58PM (#723937)

          Also, it's unclear to me if the reverse osmosis process normally used for desalination can even be used to extract elemental magnesium from seawater, so a different (perhaps more energy hungry) process might be needed.

          Apparently there is just one company ("US Magnesium") remaining in North America producing "primary" magnesium (that is material which is not recovered from existing products). They actually do extract it from water from the Great Salt Lake in Utah (which has a much higher concentration of magnesium than seawater, about 5 parts per thousand) using an electrolytic process.

          Unfortunately the US government's annual reports [usgs.gov] do not disclose the US production amounts. It was about 10% of global production in 2008 but China's production has roughly quadrupled since then, and the US production is probably proportionally less.

          I can't find a good figure of the total energy usage of the process used but I expect it is quite large as it involves very high temperatures and evaporation of large amounts of water. Apparently they have 300km² of evaporation ponds [usu.edu] which apparently represents the world's single largest industrial use of solar energy (well, at least when that was written a decade ago). Neat eh?

  • (Score: 2) by fritsd on Tuesday August 21 2018, @03:37PM (1 child)

    by fritsd (4586) on Tuesday August 21 2018, @03:37PM (#724222) Journal

    Magnesium is cheap though:

    Once upon a time I was lucky to be on vacation in Bolzano (Nort hItaly).

    When I woke up the next morning at dawn, those humongous pink mountains we saw to the north, were the Dolomiti.

    Those are made of mostly 50-50 Calcium and Magnesium carbonate AFAIK (I don't believe they coated just the visible outside with the stuff).

    • (Score: 0) by Anonymous Coward on Tuesday August 21 2018, @10:24PM

      by Anonymous Coward on Tuesday August 21 2018, @10:24PM (#724416)

      Magnesium is cheap though

      The going rate of elemental magnesium, direct from China on eBay, seems to be about 40 USD/kg. I wouldn't call that cheap; it's relatively expensive for a common metal (and one of the most abundant elements on Earth), presumably due in a large part to the high energy cost of extraction [soylentnews.org]—at 0.15 USD / kWh that'd be about 15USD/kg in extraction energy costs alone.

  • (Score: 2) by fritsd on Tuesday August 21 2018, @05:02PM

    by fritsd (4586) on Tuesday August 21 2018, @05:02PM (#724261) Journal

    The money might be worth spending *if* the process does decrease CO2 overall and you put a high value on lowering that number.

    Yes that's very true :-) we don't yet know the full cost of *not* decreasing CO2, but this summer vacation I was well pissed off that it was 35°C! And I'm not even a barley stalk! (essential for brewing beer, which you can't drink anymore when it's 35°C anyway. and apparently when it's >=35°C for longer time the barley yield goes down "disastrously")

    But this process competes with other Carbon sequestration processes, some of which may be cheaper, is my sincere hope.

    I read (a little bit) about biochar: biochar [wikipedia.org]
    - plant cheap and fast-growing trees
    - let the trees do all the work of the Carbon sequestration as if their lives depend on it, and wait 20 years (repeat every year, of course)
    - pyrolyze (i.e. burn but with only the oxidizers of the tree itself, sealed off from air) the wood. This should give enough energy that you only need to set the wood on fire, so it costs little.
    - take the gases to burn to heat something else, and drain the tar to make turpentine or something else useful. A large part of the original sequestered CO2 stays in the form of biochar.
    - the charcoal can be stuck underground, it improves the soil and gets consumed only very slowly, so it can delay the worst of Climate Change over a period of 1000 years or so.

    As long as forest fires are rare this should work? Has anyone done the maths? (Not me).