Busy weeks - We are preparing several new EW experiments

During spring and early summer 2025 we are preparing new and updated experiments that will help us understand enhanced weathering better.

(Re-) Loading the XXL Lysimeters

Three years ago, in May 2022, we built our XXL Lysimeter experiment. 20 large 300-liter water buckets were converted into lysimeters using the in-situ soil. We used four basalt treatment amounts (0, 100, 200, and 400 t/ha of basalt) with 4 replicas each. In a 5th variation we used the same rock, but further crushed to a fine dust (<25 µm), at a rate of 200 t/ha, on 4 more pots. Since inception, over a period of now more than a 1000 days, we took water samples and then drained the remaining water from the tanks, initially every 2 weeks, then every 4 weeks and most recently every 3 months. The samples were analyzed for over 40 parameters.

Unfortunately we found out that this rock/soil combination just doesn’t do notable CDR (we call it the “cation eating monster soil”), at least not when measured using leachate alkalinity over a time of 3 years.

So we decided to continue this experiment only with 5 pots (one for each of the 4 treatments plus one control), kill 15 of the 20 pots and refill the pots with different rock/soil combinations. During the dismantling of the pots we took a lot of soil samples so we can possibly find out what happened in the soil which resulted in no CDR - even over this long time.

For the new pots we are using a soil from the Cologne/Germany area (400 km away, provided by our friends at AEROC) which looks promising from the analysis data. Most pots with treaments were treated with 40 t/ha of a superfine Greenland rock dust (provided by Rock Flour Company, thank you!) which features grain sizes in the single digit microns. This dust has been milled down over thousands of years by the glaciers of Greenland. Three other rock dusts have also been used. Finally we also placed alkalinity sensors from Everest Carbon for MRV into the pots, more on that later.

Here is a video of what happened last Saturday:

Here is a time lapse video of the whole day:

(Re-) Building the world’s largest greenhouse experiment for EW

After dismantling 80% of our 2023/2024 greenhouse experiment (reduction from 400 to 80 pots, the remaining ones will run for 1-2 more years) we are going to prepare our next experiment, twice the size!

We are planning to do more than 600 pots, but with an updated layout-strategy, based on the results from the previous experiment. We are significantly shifting our approach. Rather than extensively replicating a smaller number of soil-rock combinations (as we did 2023/2024), we have chosen to deliberately prioritize testing a broader diversity of combinations, each with fewer replicates. This strategic pivot aims to maximize the number of soil types and rock amendments assessed, responding to our earlier findings that highlighted the dramatic variability in CDR outcomes depending on specific soil-rock interactions (see “Why we are ditching most replicates in favor of having more variations”).

So a week ago we prepared the first 22 soils for our new greenhouse experiment for enhanced weathering. These soils are from all over Germany, Denmark and Ireland and from various european countries. About 15 more soils from all over the world (from Australia, India, Africa, and the Americas) are expected to arrive over the summer and will also be used in the greenhouse (if everything works out fine with the logistics).

On one day we sieved and thereby homogenized more than 10 tons of soil in total. From each soil we took various samples, some of them will be sent to a lab immediately for analysis, other samples will be stored in case more analyses are needed in the future. Our goal was to homogenize the soils and to remove stones, roots, etc, so when we create pot experiments each of the pots will contain pretty much the same soil.

We worked almost from dusk til dawn. Here is a video documentary:

The next work package is to build the hundreds of new experiment pots. That will be fun (and strenuous). Stay tuned for more details coming in the coming weeks.