Can we actually measure the CO₂ removed by enhanced rock weathering?
Yes, but it's not as simple as sticking a probe in the ground. The key is that ERW works by dissolving crushed silicate rock, which releases alkalinity into soil water; this alkalinity eventually reaches rivers and the ocean, where it locks away CO₂ for thousands of years. The most direct way to measure this is to track the alkalinity leaving the field site. A large-scale field trial on an oil palm plantation in Malaysia did exactly that: over three years, they measured alkalinity in stream water from treated and untreated catchments. In one of three plot pairs, the treated catchment showed about 1 tonne more CO₂ removed per hectare per year than its untreated neighbor [4]. That's a real, measurable difference—proof that verification can work in the field.
But the same study also found that two of the three plot pairs showed no significant difference between treated and untreated catchments, because the background weathering of carbonate fertilizers was already high [4]. This means that to get an accurate signal, you need a good baseline—ideally a paired untreated plot—and you need to account for other sources of alkalinity. A 2022 modeling study of river chemistry supports this: it found that rivers can carry the dissolved products of ERW without re-releasing CO₂, so transport isn't a bottleneck, but the authors stress that real-world kinetics and added emissions from mining and spreading rock must be factored in [6].
Why can't we just use carbon isotopes to verify ERW?
Carbon isotopes—specifically the ratio of carbon-13 to carbon-12 (δ¹³C) and radiocarbon (¹⁴C)—have been used to prove that newly formed carbonate minerals came from atmospheric CO₂. But a 2023 study that ran year-long wet-dry cycle experiments on several rock types found that these isotopic signals can be deceptive. For example, when brucite and wollastonite reacted with CO₂, the δ¹³C values actually decreased, which is the opposite of what you'd expect if atmospheric CO₂ was being incorporated [1]. The authors explain this as a kinetic fractionation effect caused by the carbonation reaction being limited by CO₂ supply. In other words, the isotope signal got scrambled.
The same study found that radiocarbon (¹⁴C) did show modern carbon being incorporated into the rock powders—up to +0.55 F¹⁴C for brucite and +0.53 F¹⁴C for wollastonite—which is strong evidence of atmospheric CO₂ capture [1]. But for kimberlite residues, the radiocarbon signal was much weaker (+0.27 F¹⁴C) and was attributed to CO₂ exchange rather than net sequestration. The bottom line: isotopes can help, but they are not a standalone verification tool. They need to be combined with other measurements like total inorganic carbon (TIC) and mineral quantification.
What new tools make ERV verification market-ready?
The biggest recent advance is a novel in-situ sensor that measures alkalinity efflux directly and continuously in soil leachates, transmitting data via the Internet of Things (IoT) [3]. This sensor, described in a 2025 paper, provides real-time, high-resolution data on how much alkalinity is leaving the field after a rain event, which is exactly what carbon markets need for transparent monitoring, reporting, and verification (MRV). The author claims it significantly reduces measurement costs and improves scalability, which could be a game-changer for ERW projects seeking carbon credits.
Beyond sensors, a 2025 perspective paper argues that life cycle assessment (LCA) can strengthen MRV protocols by providing holistic emission factors, accounting for co-benefits like reduced fertilizer use, and addressing uncertainty [2]. This is echoed by a 2026 study from the UK's GGR-D Programme, which proposes a harmonized accounting framework across six CDR methods, including ERW, and notes that data gaps exist mainly for non-carbon metrics (e.g., biodiversity impacts) rather than for the core carbon removal itself [5]. Together, these developments suggest that the verification toolbox is expanding rapidly, moving from academic experiments toward practical, market-ready solutions.
About These Sources
This answer is built on 6 peer-reviewed studies — published from 2022 to 2026, 3 from 2024 or later, 3 in Q1 journals, collectively cited 136 times — selected as the most relevant from 8 studies that passed quality screening, drawn from 31 papers retrieved from a database of over 500 million.
Sources used in this answer
Impact of wet-dry cycles on enhanced rock weathering of brucite, wollastonite, serpentinite and kimberlite: Implications for carbon verification
In year-long wet-dry cycle experiments, brucite and wollastonite showed substantial carbonation (TIC increased from 1.22% to 5.98% and 0.22% to 1.01%, respectively), but δ¹³C values decreased due to kinetic fractionation, showing that stable isotopes alone can mislead; radiocarbon (¹⁴C) confirmed modern CO₂ capture in brucite (+0.55 F¹⁴C) and wollastonite (+0.53 F¹⁴C), but not in kimberlite.
Life Cycle Assessment in the Monitoring, Reporting, and Verification of Land-Based Carbon Dioxide Removal: Gaps and Opportunities
A perspective comparing LCA studies and MRV protocols for four land-based CDR methods (including ERW) finds that LCA can support MRV by providing insights into baselines, additionality, uncertainty, and co-benefits, but recommends future research prioritize timing, permanence, and dynamic modeling.
In-Situ Alkalinity Efflux Monitoring: A Novel Sensor for ERW Applications
A novel in-situ alkalinity-efflux sensor provides real-time, continuous monitoring of alkalinity in soil leachates via IoT, offering high temporal resolution data that reduces MRV costs and improves scalability for ERW carbon credit markets.
Quantification of CO2 removal in a large-scale enhanced weathering field trial on an oil palm plantation in Sabah, Malaysia
In a 3-year field trial on an oil palm plantation in Malaysia, one of three treated catchments showed ~1 tCO₂ ha⁻¹ higher removal via alkalinity export than its paired reference catchment, but two plots showed no difference; soil carbonate increased by ~0.03 wt% CaCO₃ in the top 30 cm of treated soils.
Toward Credible Carbon Dioxide Removal: Harmonized Accounting and Data Gaps Across Six CDR Approaches
Drawing on five years of UK GGR-D Programme research, a harmonized MRV framework for six CDR approaches (including ERW) finds that data coverage is uneven, particularly for non-carbon metrics, posing risks for sustainability assessments and carbon market credibility.
River chemistry constraints on the carbon capture potential of surficial enhanced rock weathering
A conceptual model of river/stream carbonate chemistry estimates global riverine carbon transport potential for accelerated silicate weathering at 7.1–21.3 GtCO₂ yr⁻¹, concluding that river transport is unlikely to be a primary bottleneck for ERW, but future research on reaction kinetics and added emissions is needed.