Project Carbdown Greenhouse: Experiment Extension Week

Last week, exactly 365 days after setting up the first experiments, we have extended our greenhouse experiment with 78 new lysimeter experiments to now close to 400 experiments in total. We are closely following last year’s building recipe, of course.

Again we are using the LUFA 2.2 soil and LUFA 6S soil to which we have added 6 rock dust amendments: basalt, dunite, steel slag (all three are the same as last year), plus three new ones: calcite (“lime” from Müllerkalk), crushed cement (from university FAU Erlangen) and a superfine glacial dust from Greenland (from University of Copenhagen). This brings our setup now to a total of 14 different rock dusts and 18 different soils.

Before we started in the greenhouse we built and programmed 86 soil pCO2 sensors which record the CO2 concentration in the soil at ca. 15 cm depth inside the lysimeters every minute and send the data to our cloud-based analysis pipeline.

In the greenhouse the first step is to homogenize the soil. The LUFA 6S soil has a lot of clay and is very dusty when fully dried.

Then the lysimeters need to be prepared. We are using food-grade buckets which are converted into the upper and the lower part.

On the second day we started to actually build new experiments by mixing soil and amendments into the buckets. For some soils and amendments this is a very dusty job…

This video shows how table 1 filled up with new buckets in the afternoon of the second day:

At the end of day 2, just 1-2 hours after mixing, our pCO2 sensors already picked up notable differences in CO2 concentrations in the soil: we already see a „signal“ from rock dust amendments in the pCO2 sensor data! The pCO2 range goes from 130 ppm (steel slag) over 1200 ppm (control, dunite) to 6250 ppm (with calcite). Soil: LUFA 2.2

Work continued on the 4th day (we needed to wait for some deliveries) when we finalized the experiments. We installed teabags with 5g of rock dust in the new lysimeters (will be pulled out in 1-2 years for analysis), installed the irrigation system and added 3g of grass seeds.

Here is a time lapse video that shows the finishing touches to table 0 (LUFA 2.2 soil) with 7 amendments: irrigation system, tea bags with 5g of rock dust, 3g of grass seeds and finally the fluxmeter army.

A huge thank you goes out to all the people who have helped preparing this effort and all the the helping hands this week!