Earth's Natural Carbon Removal Process: How the Long Term Carbon Cycle Removes CO2

Earth’s natural long-term carbon cycle removes carbon dioxide (CO2) from the atmosphere through weathering, a chemical reaction that occurs between volcanic rock, CO2, and water.

The cycle, which normally takes millions of years, involves rain interacting with CO2 and breaking down rocks, which are then transported by rivers into the ocean for use in shells and corals.

Without this carbonate-silicate cycle of water interacting with volcanic rocks to remove CO2 from the atmosphere, Earth would look like Venus.

A vivid example of the process of CO2 turning into rock is visible in the White Cliffs of Dover, which are made up of the calcium carbonate shells of algae which sank to the seafloor and built up over millions of years.1)

This same process of the long-term carbonate silicate cycle has lead to 99.9% of all carbon on earth being stored in solid form as rock, in sediment, limestone (CaCO3), or dolomite (green box).2)

The amount of carbon in the atmosphere as CO2 is only .00095% of the total carbon on Earth (red box). Our climate change problems are being caused by the approximate 1/3 increase in this amount since pre-industrial times.

Total yearly global CO2 emissions are now 40-100 times greater than the amount of CO2 the carbon cycle typically converts into carbonate rocks in a year.3)

At certain times in geological history, when tectonic forces have exposed large quantities of volcanic rock in humid, tropical latitudes, it has greatly increased the rate of CO2 removal from the atmosphere.

Accelerated Rock Weathering Can Work To Remove CO2 Levels On a Global Scale

Observe how after volcanic rocks (orange), are exposed near the equator (green), ice extent then increases (blue). See: 450 Ma, 360 Ma, and 30 Ma

The Last 3 Ice Ages Were Influenced By Increased Volcanic Rock Weathering Near the Equator

Over geological timescales, CO2 levels and the temperature of the climate are regulated through the exposure and weathering of volcanic rock, especially near the equator. Weathering has a stabilizing effect, so as the planet gets hotter from increased CO2, weathering rates increase and CO2 is more rapidly removed. For this reason, weathering is referred to as the “global thermostat.”4)5)

A paper published in the April 20196) issue of Science, adds to the accepted body of evidence that the last 3 ice ages were caused by the exposure and weathering of volcanic rock near the humid tropics.

The accompanying gif and graphs show how volcanic rock exposed near the equator correlates with increases in planetary ice cover.

Starting around 50 million years ago (Ma), as the Himalayan Plateau begins to rise, so too does ice cover. Observe how, as volcanic rock (orange) becomes present near the equator (green), ice coverage begins to increase (blue).

On geological timescales, nearly all of the weatherable rock on Earth that is exposed has already weathered and built up a coating on it that inhibits the weathering reaction. Other forces such as landslides, glacier melt, etc can expose new weatherable rock, but if it is stationary, the weathering reaction will slow down soon thereafter.

Project Vesta seeks to mimic Earth’s natural carbon cycle, but to combine and accelerate the steps where CO2 is removed from the atmosphere.

We plan to efficiently mine, mill, and transport large quantities of the highly-abundant and fastest weathering rock: Olivine.

Then we will place it on the shores of warm, high-energy beaches where wave motion will grind the rock into finer pieces and continually remove the coating that normally builds up on the surface and slows the reaction.

Last updated on April 22, 2020
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