4 min read

#40 - Enhanced Rock Weathering cheat sheet

#40 - Enhanced Rock Weathering cheat sheet

What is Rock Weathering?

Centuries after centuries, rain falls on mountains and erodes them. Rock material slowly dissolves in water, a phenomenon called chemical weathering. Here is how it works.

First, atmospheric carbon dioxide dissolves in rainwater, which forms carbonic acid.

  • H2O + CO2 -> H2CO3

When the rain falls and hits the ground, the carbonic acid can turn into bicarbonate, a negative ion.

  • H2CO3 -> H+ + HCO3-

Bicarbonate combines with positive ions contained in the rock, such as Mg2+ or Ca2+, and is caught by runoff water, transported in the waterways, and ends up in the ocean.

The CO2 initially captured in the atmosphere remains trapped in the ocean, permanently stored in solid carbonate minerals or ocean alkalinity for thousands of years. CO2 is therefore locked in a stable form in the long carbon cycle.

This phenomenon has been happening naturally since there's been rain on Earth. It is responsible for regulating the CO2 concentration in the atmosphere.

Enhanced Rock Weathering to fix the climate crisis

Just like photosynthesis, Earth has provided us with a powerful tool to remove CO2 from the atmosphere. However, natural rock weathering occurs at a very slow pace, prompting the need for ways to enhance the process. We don't have the time!

The idea of Enhanced Rock Weathering (ERW) is to spread crushed rock, typically basalt, onto fields to accelerate the process from centuries to just a couple of years.

Milling the rock material into sub-millimetre grain sizes accelerates weathering rates. By reducing basalt to powder, there's increased surface contact with the environment, expediting chemical reactions.

Basalt is a common byproduct of mining, abundantly available around the world, and contains useful minerals for rock weathering and CO2 capture.

ERW also provides tremendous co-benefits for farmers, ultimately increasing crop yields:

  • enhances soil fertility
  • buffers soil acidity
  • reduces NO2 emissions

Selling carbon removals to fund ERW deployment at scale

Enhanced rock weathering is a carbon removal technology; the CO2 removed from the atmosphere can be sold on the carbon markets. The amount varies based on soil type, rock type, and regional weather.

Roughly, 10 tonnes of CO2 per hectare can be sequestered. Implementing ERW globally could potentially sequester up to 2 billion metric tonnes of CO2 annually.

New carbon accounting and monitoring standards have emerged to help developers quantify, certify and ultimately sell carbon credits. Puro.earth and Isometric methodology are paving the way, with buyers showing booming interest.

Enhanced rock weathering carbon removal sales grew 600% last year!

Some challenges revolving around measuring the exact impact of the solution remain:

  • How much CO2 is actually removed?
  • How long is the CO2 locked away?
  • What is the exact impact on crops?

Low barriers to entry for ERW could lead to the rapid emergence of opportunistic companies and low-quality projects, resulting in negative press and damaging the entire sector. Let's not allow this to happen!

Enhanced Rock Weathering Ecosystem Map

Applying alkaline rock dust in fields is cost-effective and utilises existing infrastructure. The technology is deployable now, leading to a proliferation of ERW startups in recent years.

We're currently witnessing the emergence of the ecosystem, with carbon removal quantities still at anecdotal levels, as shown on the leaderboard below (data from CDR.fyi).

The ERW market is primarily driven by off-take agreements.

Only a few thousand tonnes delivered yet but the market is poised for growth!

Thank you for reading!
Colin Rebel
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