Captain Drawdown’s daily logbook on every CDR story, paper, and expert voice — so you don’t have to read them all.
Two preprints on ocean alkalinity enhancement (OAE) posted to CDRXIV frame the same regulatory problem from opposite ends. One argues the lab evidence base is being generated at doses no real deployment would produce. The other reports a field trial that found no harm. The gap between them is the permitting question: what counts as a “realistic” perturbation when regulators write environmental review protocols for marine CDR?
The lab critique
Bach and co-authors, in Lethal by design? Guiding environmental assessments of ocean alkalinity enhancement toward realistic contextualization of the alkalinity perturbation, argue that OAE ecotoxicology studies routinely dose organisms at alkalinity concentrations that would never occur in an actual deployment plume. The consequence is a literature biased toward “harm found” conclusions that regulators then inherit as the default evidence base. Their fix is to anchor lab exposures to the concentration profiles a real plume would produce.
The field result
Jankowska and co-authors, in Olivine-based marine carbon dioxide removal field trial shows no adverse effects on the benthic community, report on a 2022 marine enhanced rock weathering (ERW, applying crushed silicate rock to accelerate natural CO2 uptake) deployment in Polish coastal waters using olivine. They found no measurable harm to the seafloor community. This is the empirical counterweight to Bach’s critique, and the kind of in-situ evidence that permitting authorities have said they want.
Matched dimensions
- Evidence type. Bach: methodological critique of lab ecotoxicology. Jankowska: single field trial, benthic monitoring.
- Direction of finding. Bach: current protocols overstate harm. Jankowska: no harm detected in the field.
- Dose realism. Bach: argues most published exposures are unrealistically high. Jankowska: dosed at a real deployment concentration by definition.
- Regulatory usability. Bach: reframes how lab inputs should be designed. Jankowska: provides a specific site-specific null result.
- Generalizability. Bach: applies across the OAE literature. Jankowska: one feedstock, one site, one benthic community.
Where they converge
Both papers point at the same missing piece: nobody has forced the modeling, ecotoxicology, and field-trial communities to agree on what plume concentrations a commercial OAE project would actually produce. Work like A framework for understanding efficiency losses of Ocean Alkalinity Enhancement by Lunstrum et al. quantifies how much of a dose becomes durable CO2 uptake. Regional modeling like A comparison of metrics for CO2 uptake efficiency of regional ocean alkalinity enhancement in an Earth system model by Teske, Kemena, and Oschlies defines the uptake side. Both are inputs Bach’s “realistic perturbation” framing needs. Neither is currently wired into the ecotox protocols.
Where they diverge
Bach’s paper is a claim about the whole evidence base. Jankowska’s is one data point. A regulator reading both could reasonably conclude either that the lab literature is systematically pessimistic and needs redesign, or that one benign field result is not enough to overturn precautionary lab defaults. The two papers do not resolve each other. They define the axis a permitting decision has to sit on.
So what
For anyone designing OAE protocols now, whether developers, buyers, or registries, these two preprints are not additive data. They are two different templates for how environmental review would get done. Site-suitability work like Mapping the future of ocean carbon dioxide removal in Australia by Benjamin et al. is already downstream of that unresolved question. You cannot finalize deployment maps without knowing which framing the reviewing body will use for ecotoxicology inputs.
The specific thing worth watching is whether the next round of environmental assessment guidance, from a national regulator or a major crediting registry, cites both papers side by side, and whether it adopts Bach’s realistic-perturbation standard for laboratory inputs or defaults to the fixed-concentration protocols already in circulation. That choice is the one that matters for the near-term OAE permitting pipeline, and it is a choice that has not been made yet.
For readers new to the underlying chemistry, What Is Enhanced Weathering? A Primer covers the land-based analog to what Jankowska’s team tested in the marine setting. The lab-versus-field tension is not unique to OAE, but OAE is where it will get resolved first.
Citations
- Cdrxiv — Lethal by design? Guiding environmental assessments of ocean alkalinity enhancement toward realistic contextualization of the alkalinity perturbation
- Cdrxiv — Olivine-based marine carbon dioxide removal field trial shows no adverse effects on the benthic community
- Cdrxiv — A framework for understanding efficiency losses of Ocean Alkalinity Enhancement
- DOI-resolved paper — A comparison of metrics for CO2 uptake efficiency of regional ocean alkalinity enhancement in an Earth system model
- DOI-resolved paper — Mapping the future of ocean carbon dioxide removal in Australia