Update: Our three main enhanced weathering experiments

Over the past three years we have run three enhanced weathering experiments in fields and in a greenhouse in which we are using various monitoring approaches to assess the carbon dioxide removal effects. Here is an overview of these experiments.

XXL Lysimeter Project

In May 2022 we set up 20 large 300-liter water buckets converted into lysimeters using the in-situ soil. We used four basalt treatment amounts (0, 100, 200, and 400 t/ha of Eifelgold basalt, grain size up to 2,000 µm, EW potential approx. 450 kg CO₂ per ton of rock) 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 700 days, we took water samples 18 times 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. Our data contain 376 leachate analyses and more than 3 Mio sensor measurements including EC, pH, humidity and temperature of soil and tanks as well as environmental data from a professional weather station.

Alfalfa Experiment in Greece

Our EW field experiment in Larissa/Greece started in June 2022 and features local agricultural soil combined with Greek olivine rich rock dust in 3 variations with 5 replicates each: untreated controls, 50 t/ha and 100 t/ha rock dust. We installed 5 macrorhizons in each replicate, allowing soil pore water collection every 2-6 weeks. Three out of every 5 replicates also contain a lysimeter for the collection of leachate water. Our data contain analyses of 317 pore water samples and 134 leachate water samples as well as more than 1 million sensor measurements.

Greenhouse Experiment

Since January 2023 we have been running a greenhouse experiment. We have up to 400 experiment pots with up to 100 variations of 17 soils and 14 feedstock materials, including soil from the same field and the same Eifelgold basalt that was used in the XXL lysimeters. Leachate and soil samples are analyzed monthly or quarterly and we monitor soil pCO₂ and CO₂ efflux using electronic sensors. Our data cover about 4,000 leachate analyses, a few million sensor measurements and a large CO2 efflux dataset from our fluxmeter robot army. Please refer to our blog article/paper “Insights from monitoring leachate alkalinity, pCO₂ and CO₂ efflux of 400 weathering experiments over one year” for more information.

Dirk Paessler