Olivine comes from Norway, which uses hydro power. The energy in extracting and crushing is around 4kg CO2/ton. Pulverizing is around 30-50kgCO2/ton rock. Majority of transport is on water (ocean, river), which is low emissions. In the end, for every ton of rock around 850kg of CO2 are removed.

For basalt, it's around 200kg net, so the supply chains have to be shorter.

I checked my math with the DOE's experts, and it checks out.

Source for the numbers?

Yes, further details would be very illuminating !

Sibelco's Aheim mine essentially supplies a large part of the world's olivine today. It is located in a Fjord with its own port. The transportation distance is very small.

See their website here: https://www.sibelco.com/en/150-years/aheim

"The proximity of Aheim’s mine, processing facility and shipping terminal enables Sibelco to run a highly efficient operation with minimal transport or double-handling of materials. Quarried olivine is moved via conveyor belt through a 4km tunnel to the processing plant where it is crushed, dried and screened into different grades."

When transporting mostly by ship, olivine ERW efficiency can remain >90% even with 1000+ kilometers of sea transit.

See this working paper: Environmental life cycle assessment of CO2 sequestration through enhanced weathering of olivine https://legacy.projectvesta.org/wp-content/uploads/2019/06/E...