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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.
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(Score: 1, Insightful) by Anonymous Coward on Monday August 20 2018, @05:31PM (4 children)
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
Yeah, might be easier to start injecting sulfur compounds [technologyreview.com] into the upper atmosphere.
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 2) by Zinho on Monday August 20 2018, @06:37PM (2 children)
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.
"Space Exploration is not endless circles in low earth orbit." -Buzz Aldrin
(Score: 1, Insightful) by Anonymous Coward on Monday August 20 2018, @08:19PM (1 child)
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.
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
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?