Dirk Paessler

Remy 0.9 is out 🐀 — my open-source plugin that lets Claude work in shared Google Docs now writes native suggestions: real Accept/Reject buttons, even on comment-only links. Not one character changes without a human click. AI drafts, you decide. github.com/dirkpaessler/remy

This last part of our XXL Lysimeter Experiment is about plumbing, and it's not glamorous: keeping measurements trustworthy over years is harder than the chemistry itself. Our on-site rain gauge under-caught by nearly half against the official station. Anchor to an official reference, always.

None of this argues against in-situ MRV. It argues for engineering it properly: anchor your gauges, over-provision your sensors, report coverage honestly.

This last part of our XXL Lysimeter Experiment is about plumbing, and it's not glamorous: keeping measurements trustworthy over years is harder than the chemistry itself. Our on-site rain gauge under-caught by nearly half against the official station. Anchor to an official reference, always.

A soil-CO₂ sensor sounds like the ultimate shortcut. Weathering consumes CO₂, so bury a probe and read carbon removal straight out of the ground. Part 5 of our XXL Lysimeter Experiment shows why that's not how it works, and what these sensors are actually good for instead.

And the basalt dose barely moves any of it. Every treatment overlaps control, the same verdict every other instrument in this series has returned. Soil-CO₂ sensors won't count your carbon. But they're a genuine window into the soil as a living system, and that's worth building.

A soil-CO₂ sensor sounds like the ultimate shortcut. Weathering consumes CO₂, so bury a probe and read carbon removal straight out of the ground. Part 5 of our XXL Lysimeter Experiment shows why that's not how it works, and what these sensors are actually good for instead.

Here's the catch. Soil CO₂ strongly predicts leachate pH, but only weakly tracks the alkalinity that actually leaves the pot. The gas is the cause at the top of the chain.

A soil-CO₂ sensor sounds like the ultimate shortcut. Weathering consumes CO₂, so bury a probe and read carbon removal straight out of the ground. Part 5 of our XXL Lysimeter Experiment shows why that's not how it works, and what these sensors are actually good for instead.

We logged soil CO₂ daily in all 20 pots for four years. Soil CO₂ ran 5 to 20 times higher than outside air, breathing hard in summer and collapsing in winter. Two things throttle that breath: warmth drives it up, but past about 18°C the soil dries out and the breath falls despite the heat.

Alkalinity is the number we actually care about, and it's slow and expensive: pump the leachate, ship it to a lab, titrate. Part 4 of our XXL Lysimeter Experiment asks a more practical question: can a sensor buried in the soil, logging continuously, stand in for that lab work?

Next: we test whether soil CO₂ itself carries a weathering fingerprint.

Alkalinity is the number we actually care about, and it's slow and expensive: pump the leachate, ship it to a lab, titrate. Part 4 of our XXL Lysimeter Experiment asks a more practical question: can a sensor buried in the soil, logging continuously, stand in for that lab work?

One caveat we're stating plainly: this calibration is specific to our soil and climate. It won't transfer cleanly to another site without re-anchoring against real leachate samples there.

Alkalinity is the number we actually care about, and it's slow and expensive: pump the leachate, ship it to a lab, titrate. Part 4 of our XXL Lysimeter Experiment asks a more practical question: can a sensor buried in the soil, logging continuously, stand in for that lab work?

Since leachate EC is already a strong proxy for lab alkalinity, the buried probe reaches alkalinity through that chain.

Alkalinity is the number we actually care about, and it's slow and expensive: pump the leachate, ship it to a lab, titrate. Part 4 of our XXL Lysimeter Experiment asks a more practical question: can a sensor buried in the soil, logging continuously, stand in for that lab work?

Part 2 of our XXL Lysimeter Experiment left the leachate data flat. Part 3 turns to the buried sensors, and the picture changes.

Takeaway: cheap, continuous sensors carry real signals about weathering flux between expensive lab tests.

Part 2 of our XXL Lysimeter Experiment left the leachate data flat. Part 3 turns to the buried sensors, and the picture changes.

It holds in every pot, control included. This is the soil's seasons at work, not the basalt.

Part 2 of our XXL Lysimeter Experiment left the leachate data flat. Part 3 turns to the buried sensors, and the picture changes.

Does more basalt mean more CO₂ removal? Our XXL Lysimeter Experiment says: not so fast. The intuition is a straight line. Spread twice as much rock, remove twice as much carbon. Over 1,400 days of our XXL Lysimeter Experiment, that line does not hold.

This isn't an argument against enhanced weathering. It's an argument against assuming dose-response instead of measuring it. Any MRV approach that credits "more rock, more CDR" without a real control on the real soil is crediting a guess.

Does more basalt mean more CO₂ removal? Our XXL Lysimeter Experiment says: not so fast. The intuition is a straight line. Spread twice as much rock, remove twice as much carbon. Over 1,400 days of our XXL Lysimeter Experiment, that line does not hold.

The baseline is large, and part of it isn't weathering at all. It includes a disturbance flush from when the soil was first built and soaked. Four replicate pots isn't much statistical power. A modest but real effect could easily hide inside these error bars.

Does more basalt mean more CO₂ removal? Our XXL Lysimeter Experiment says: not so fast. The intuition is a straight line. Spread twice as much rock, remove twice as much carbon. Over 1,400 days of our XXL Lysimeter Experiment, that line does not hold.

Every treatment's error bars overlap the control. Whatever the basalt is doing here, it's smaller than the pot-to-pot noise of the soil itself.

Does more basalt mean more CO₂ removal? Our XXL Lysimeter Experiment says: not so fast. The intuition is a straight line. Spread twice as much rock, remove twice as much carbon. Over 1,400 days of our XXL Lysimeter Experiment, that line does not hold.

1,400 days. Four winters. Twenty pots of basalt-amended soil. That's our XXL Lysimeter Experiment, and the treated pots removed no more CO₂ than the untreated controls.

Turns out we picked the wrong soil-feedstock pairing for this site. A parallel greenhouse trial confirmed it. The upside: our buried sensors found something better. Daily CO₂ data showing how the soil "breathes" a seasonal cycle that drives the whole weathering process.

1,400 days. Four winters. Twenty pots of basalt-amended soil. That's our XXL Lysimeter Experiment, and the treated pots removed no more CO₂ than the untreated controls.

We ran one of the longest, most detailed enhanced-weathering field experiments out there: daily sensor logs, monthly water chemistry, four replicates per treatment.

Enhanced rock weathering has a problem that doesn't get talked about enough. It's not the science. The science works. It's that finding the right fields is slow and expensive, and verifying that the rock did its job can eat up nearly half of total project costs.

The result is ERW projects that are cheaper to start, cheaper to verify, and easier to finance. AEROC doesn't compete with project developers. It makes them more effective. That's the kind of infrastructure the ERW industry needs right now.

Enhanced rock weathering has a problem that doesn't get talked about enough. It's not the science. The science works. It's that finding the right fields is slow and expensive, and verifying that the rock did its job can eat up nearly half of total project costs.