Green Sharp Sand Beaches As A Carbon Drawdown Technology?

Sign up for daily news updates from CleanTechnica on email. Or follow us on Google News

---

Carbon capture, direct air capture, and carbon direct removal are back in the hype cycle again, so yet again I’m looking at solutions that are technically interesting, if not remotely likely to scale. Under the microscope today is Vesta Earth, which is exploring olivine weathering as a beach sand supplementation scheme.

I’ve looked at multiple mineral weathering drawdown approaches. None of them to date stand up to scrutiny when you start asking probing questions:

• Where is the mineral?
• Where can it be spread?
• How will the mineral get there?
• How finely does the mineral have to be crushed to most effectively absorb CO2?
• How much CO2 does it absorb on a mass to mass ratio basis?
• How much energy does it take to crush the mineral to that fineness?
• How long does it take for the weathering to occur?
• What is the carbon debt of the above?
• What is the cost of the above?
• Are there any co-benefits?
• Are there implications for ecosystems where the mineral is spread?
• Will it have other impacts that make it non-viable?
• What could we do with the money instead?

So, to Vesta Earth. As noted, its solution is olivine weathering. What’s olivine? It’s a common mineral, magnesium iron silicate. It’s very abundant in the earth’s crust. Very pure forms of it are crystalline and used to make the semi-precious gems called peridot. Most of it is just a big mix of various forms of igneous rocks and minerals, that is to say cooled lava.

Underground, it just sits there like any other rock. Bring it up into the atmosphere, however, and it starts reacting with carbon dioxide to make magnesium carbonate. It does that in water too. If you’ve been reading my recent series on ocean geoengineering, you might remember that Planetary Technologies also ends up with magnesium carbonate, but gets there by adding milk of magnesia — magnesium hydroxide — to ocean waters. One ton of finely crushed olivine, down to the level of sand or below, can absorb a ton of CO2.

Olivine weathering is one of the go-to approaches because olivine is so common and because of this reaction. A couple of papers I reviewed point to a Nature journal publication of CO2 Disposal by Means of Silicates by Walter Seifritz in 1990 as the first mention of mineralization as a carbon drawdown solution. It’s unclear to me why a Norwegian nuclear scientist whose career was mostly devoted to nuclear explosives for military and civilian use ended up being the first to propose mineralization for carbon drawdown, but reality is often weird. The proposal turns out to be a brief letter of around 250 words that suggests calcium silicate and a chemical reactor for enhanced weathering.

And so an academic industry was born, and 34 years later there’s still exactly zero commercialized mineralization, although there are certainly startups getting venture capital money to do silly variants of it, for example Heirloom’s Rube Goldberg circulating trays of quicklime slurries funded by Breakthrough Energy Ventures.

What else is olivine? Well, it’s green. I can’t tell if it’s an attractive green or just a distinctive green, being colorblind, but the grand total of four beaches in the world that are olivine heavy are tourist attractions because it’s unusual. I’d share pictures I’ve looked at, but none are permitted for republication and so I had ChatGPT create a variant. It looks vaguely like Papakōlea Beach in Hawaiʻi, where apparently locals have a habit of blocking the single road in and shaking down visitors for shuttle fees.

Vesta Earth’s primary idea is to mine olivine, grind it into sand, and add it to beaches that are being washed away by storms and tides, now enhanced by sea level rise and bigger storms. It hopes to do that in conjunction with communities around the world in the coming years and decades.

It’s going to run into a specific roadblock. Communities like their beaches the color and softness that they are. Beaches that look like ground up beer and soda bottles will be a tough sell. Further, the hardness and sharpness of freshly ground olivine will have a distinctly different feel than many common beach sands. Florida’s sands are soft and white because they are silica quartz ovals and ground sea shells. Olivine would be a tough sell.

Communities restore beaches because of the economic value of beaches. For example, one study I read found that about 50% of Florida’s economy was tied to its beaches. New sand to replenish beaches is a big business. Degrading the quality of the beaches would probably not be saleable and beaches with no economic value don’t get replenished.

Communities can’t afford beach replenishment on their own so have to cobble together federal, state, county, and municipal money to get beaches replenished. This might be in Vesta’s interest if they can link funding for carbon drawdown, but it runs into other challenges.

Beach erosion, by the way, is one of the several economic hits coming for especially southern Florida, as I noted years ago. Beach erosion is increasing, high tides are increasing to the point of regularly flooding buildings and infrastructure near the water, and storm surges from hurricanes are getting bigger as hurricanes widen and increasingly intensify. But the source of southern Florida’s fresh water, the Biscayne Aquifer that’s fed by the Everglades, is deeply at risk. The Everglades are much more likely to become brackish due to sea level rise per studies that adjusted seaside elevations from legacy radar data sets with machine learning a few years ago. And the Aquifer is surrounded by Superfund sites and sprawling suburban septic tanks. Meanwhile, clear sky flooding, where salt water bubbles up from the ground, is a regular occurrence many parts of southern Florida due to the porous limestone underpinnings.

‌

Fresh water is going to get a lot more expensive. Many municipalities won’t be able to cobble together funding for beaches, so tourism will dry up. Real estate in many places will have to be abandoned. It’s a recipe for economic disaster, one which the state is doing its best to pretend isn’t happening. This is unlikely to be a place where replacing the white, soft sand of tourist-attracting beaches with hard, sharp, green sand will be a thing.

And that’s an affluent place where lots of money is being spent on beach replenishment.

So there’s a gap between the solution and acceptance of the solution. This doesn’t mean that some communities in the world won’t decide that green beaches are a great differentiator and consider annual olivine replenishment.

But then you start running into the other problems with this model, and to be clear, Vesta Earth clearly understands them and is looking at them seriously.

As noted, olivine is just cooled lava that is rich in magnesium iron silicate. It’s not pure magnesium iron silicate but comes with a wide variety of other minerals. All of them are things which will change the chemistry of the local ecosystems in some manner or other. Mining rocks in one place, grinding them up and dumping them on beaches has to be done with care in order to avoid significantly imbalancing the local ecosystem or even poisoning it.

And weathering requires spreading. Make a bunch of olivine sand and dump it in a big pile and the olivine in the middle of the pile won’t weather at all quickly.

Not that weathering is a quick process regardless. Grains below a millimeter, in the range of beach sand, will weather to 70% over 100 years. Olivine is also heavier than normal sand, so it tends to stay behind when other sands are washed away, making beaches more and more green over time, even if they start out mixed.

This suggests you can’t keep dumping olivine on the same beaches year after year, but would have to spread them across further and further expanses away from previous spots in order to allow weathering of the first spread minerals and to not disrupt ecosystems with primary or trace elements in the minerals.

Other ocean engineering processes at least have the benefit of being capable of being located on current and tide heavy areas where the ocean does the distribution, more than not, although that requires care too. The lower tendency for olivine sand to be washed away diminishes the value of that.

Vesta Earth is an olivine weathering proposal that has minor merit, but it’s unlikely that we’ll be seeing green beaches spreading around the world. Vesta has found some funding. It received a grant of $1.6 million and was seeking Series A funding. It’s a non-profit that appears to mostly be a community of academics that have been studying olivine weathering for decades and are hoping to get more research money out of it. Their science page is a litany of the ecological concerns and the research that they are doing with it. And unlike the magnesium hydroxide startup, it actually would be carbon positive.

Even then, they only think they’ll manage to scale to 10 to 100 million tons of carbon drawdown, about 0.25% of a single year’s current carbon dioxide emissions.

As I like to note, there’s an amazing nanotechnology carbon-capture solution. It comes in a tiny, dirt cheap package. Strew hundreds of them across open ground and a few find moist, mineral-rich soil. They use internally stored energy to send threads questing down and up. They make little solar panels above ground and mine for water and minerals below ground. They suck carbon out of the air and sequester in minerals over time. They spread by themselves if unchecked.

We call them trees and plants. Afforestation, reforestation, rewilding, wetland restoration, and low tillage agriculture are much more scalable wedges than thousands of green beaches. But no carbon drawdown solutions are scalable for the 2050 targets. That requires avoiding emissions by electrifying everything and making electricity low carbon.