Carbon Drawdown Initiative Innovates On A Lab Test Speeding Up CDR Research

Enhanced rock weathering is one of the most promising carbon dioxide removal techniques, but in practice, finding the right rock for the right soil has been a slow, painstaking process. Now, Carbon Drawdown Initiative says it has found very promising results in its research to slash testing times from 200+ days to just 48 hours.

The Problem: Slow, Costly Testing In The Field

In field and greenhouse trials, the team at Carbon Drawdown repeatedly saw that the same crushed rock applied to different soils can produce wildly different results — from strong carbon dioxide removal (CDR) effects to total flops. The main performance metric is the increase in alkalinity in water draining from the soil (leachate).

In their 2023–2024 greenhouse experiment with 400 pots, it typically took 200–250 days to detect whether a given rock–soil combination was working, and sometimes over a year to be sure. In real-world field trials, timelines are even longer. That means months of work, expensive monitoring, and, in some cases, spreading rock dust with zero climate benefit.

The Breakthrough: A 48-Hour “Shaker Test”

The new approach is surprisingly simple. Instead of waiting months, the team puts 30 grams of rock, 80 g of soil, and 150 g of distilled water into an Erlenmeyer flask and places it on a laboratory shaker for 48 hours. Throughout the test, they measure electrical conductivity (EC), which turns out to be a reliable proxy for the alkalinity changes that signal CDR activity.

In just three weeks, the researchers “replayed” 30 different soil–rock pairings from their 700-day greenhouse trial and saw that short-term EC results closely matched long-term alkalinity outcomes.

“With this data, we would have known in advance that some rock/soil combinations would do little or no CDR,” the team notes. “In the greenhouse, it took over 200 days to tell the difference between flops and hits.”

Why It Matters For CDR Projects

In EW projects, being on the left side of the graph — where alkalinity doesn’t increase — means wasted time, money, and carbon accounting. By identifying poor-performing combinations before large-scale deployment, project developers could avoid unproductive work and improve climate impact.

While results can depend heavily on the specific type of rock dust used, the relationship between the long-term greenhouse data and short-term lab results was qualitatively stable for a given rock type.

Still A Mystery — But Promising

The team admits they don’t fully understand why the method works so well. Hypotheses include:

• The water-rich slurry accelerates reactions.
• Continuous shaking may break up coatings on rock particles, speeding dissolution.
• The test may mimic some of the decisive processes in soils, just on a compressed timescale.

Regardless of the exact mechanism, the method’s potential is clear: a few hundred grams of material and two days in the lab could guide decisions that previously took a year of work.

The Bottom Line

If further testing confirms this approach across a wide range of soils, it could become a standard pre-screening tool for EW projects, saving time and money, and ensuring that rock applications deliver meaningful carbon removal. Find the full report here (PDF).