Carbon Removal Technologies

In general, the cost of mining, milling and grinding 1 ton of rock in large-scale mining, has been calculated to be about $7/ton. Applied to olivine, it proposed that it would be about $12/ton.

The good news is that for the initial olivine, we will attempt to utilize "tailing" piles, which are the removed rock from existing mines. It turns out that diamonds, nickel, chromite, and other commodities are found in olivine-rich rocks. And to get to them, they have to dig up massive amounts of olivine that just sits on the site in piles as "waste."

Those tailings piles are also where some of the real-world calculations for olivine dissolution rates come from. They even determined that some mines hosted in olivine-rich rocks actually more than offset their own CO2 emissions in this unintentional way.

The ideal set up for a beach project would be right on the coast (in a tropical area as temperature affects the speed of weathering), near the end of a railway that runs from an abandoned mine with tons of tailings piles.

If the trees were to burn, all of that carbon you worked so hard to sequester would be released, so it is not foolproof and decades of sequestration can be rolled back in hours. Whereas once the olivine grains are on the beach, it is going into the seafloor in a pretty much irreversible chemical reaction.

As for the rate of olivine weathering, it is the fastest of any major rock-forming silicate mineral and is further accelerated by the abrasions of rock, and by microbes. The rate of sequestration depends on the size of the particles, and how much is spread per each beach. Many of the calculations affirming the data have been measured from static piles of olivine tailings (pilings of rock that sit as "waste" in mines sites.) Those rates alone are impressive, but we are looking to utilize the beaches to further increase the rate of weathering to at least 20 microns per year. At that rate, a grain of olivine with a diameter of 100 microns will dissolve in around 5 years.

"Our experiments show that olivine grains when kept in motion weather fast because continuous mutual impacts remove reaction-inhibiting silica from the surface and tiny µm-size slivers are produced allowing a fast chemical reaction. The application of olivine and other (ultra)mafic minerals like serpentine in high-energy shallow marine environments can make a significant contribution in the fight against climate change. The counteracting effect on ocean acidification is immediate."

Here is the basic reaction:

Mg2SiO4 + 4 CO2 + 4 H2O −→ 2 Mg^2+ + 4HCO3^- + H4SiO4

CO2 is consumed, and Mg2+, Fe2+, H4SiO4 and HCO3^- are produced.

This paper has the best calculations and a lab experiment demonstrating the rate. https://climitigation.org/wp-content/uploads/2017/10/Rolling...

This one is good as well and discusses the tailing pilings and importance of microbes alone in possibly accelerating the rate up to 4,000x https://climitigation.org/wp-content/uploads/2017/10/Olivine...

Most of the ocean though is experiencing catastrophic increases in ph and need some sort of anti-acid, which is what is amazing about the reaction from olivine. It almost sounds too good to be true, but the resulting solution from the reaction is alkaline. Its addition to the water actually deacidifies the ocean in the local area.

Further, one of the breakdown products in the reaction is silicate, which is a limiting factor for diatoms. Diatoms are particularly hit hard by climate change and are important in the base of the food chain. Diatoms provide food for the entire ecosystem from fish and birds. Diatoms themselves may also actually be responsible for moving significant amounts of biomass to the deep ocean as they sink (further reducing CO2). They also compete with dinoflagellates, which are the cause of red tides and could be useful in stemming their increased occurrence by counterbalancing their rapidly increasing populations.

That said, you are right that the addition of olivine should be carefully considered, especially for specific areas. We know already to avoid areas that are adapted to acid conditions, such as peatlands, because increased alkalinity could accelerate the breakdown of peat and speedup methane release.

Given that you need to do this once every 25-40 years (maturity cycle of the tree), is doing it with drones really that big a win?

We are not planning to do any new mining for the first allotments of olivine though, as there are literally "tons" of piles of olivine-rich rock sitting as "tailings" on the property of old mines.

This already excavated rock was mined in the pursuit of the mineral deposits below it and are considered "waste" by these mines. Kind of like buying a used car instead of having a new one created, that rock's CO2 is already accounted for. So, in this case, we do not have to mine it, only transport (ideally in an efficient manner like a train) and then mill it and spread it on the beach.