Open-System Carbon Removal: Harmonizing MRV for Trust and Transparency

Can we trust that every carbon credit sold represents real, durable climate benefit? That question brought together more than forty scientists, policymakers, registry leaders, buyers, suppliers, NGOs, and verifiers at the University of Pennsylvania’s Kleinman Center for Energy Policy on September 29, 2025.

The workshop began with a clear charge: not to seek consensus, but to map where the field currently stands on measurement, reporting, and verification (MRV) for carbon removal—and to identify the major scientific, accounting, and policy questions that must be answered to move forward. Yet by the end of the day, surprising alignment by the majority of the attendees had emerged on principles needed to build trust, especially in open-system removal technologies such as ERW, OAE, and biochar.

Collaboration Across Perspectives

Six breakout tables—each mixing registries, project developers, buyers, NGOs, academics, national lab researchers, and a few government and third-party verifiers—worked through presentations and discussion prompts and then reported back to the full group. Despite the different perspectives, the process revealed a strong spirit of collaboration and areas of clear agreement.

Where We Found Agreement

• Simplicity with Guardrails: Clear, robust rules are needed from the outset—getting the system right early matters because it’s harder to change later. At the same time, simplicity and legibility can support learning and participation, as long as rules include strong safeguards and periodic reviews to avoid gaming, as we saw with past offset programs.
• Existing Standards Are Not Enough: Greenhouse gas (GHG) accounting and life-cycle assessment (LCA) standards—such as ISO 14064 and ISO 14044—provide useful foundations but fall short of what is needed for carbon-removal pathways, especially open-system approaches. Methodologies developed by registries and other standards developers—like Isometric, Puro, and Absolute Climate—provide better guidance, although they are still evolving. A central limitation of current GHG and LCA guidance is that system boundaries are not well defined, allowing different market participants to draw them in ways that can change or even inflate claimed benefits. In carbon removal, where boundaries determine whether a process is net negative, that flexibility introduces inconsistency across registries and markets, particularly when open systems intersect with sectors such as bioenergy. Several participants highlighted the value of a clear accounting framework, with the net-flux approach noted as one example of how a wide system boundary could support consistent uncertainty quantification and communication.
• Data Is a Bottleneck—and a Solution: Early projects are “commercial” in the sense that buyers are making purchase commitments, registries have methodologies, and projects are progressing through verification toward delivery. Yet the underlying science is still evolving. Participants emphasized the urgent need to share performance data widely—including negative results—to strengthen the scientific foundation and improve future project design. Smarter use and transparent sharing of existing data can accelerate learning and prevent repetition of known dead-ends. At the same time, research on landscape- and global-scale uncertainty—beyond the scope of individual projects—is critically needed, along with new funding mechanisms to support it.
• Critical and Relevant Data: Participants discussed how current MRV efforts already generate vast amounts of data—particularly for soil and geochemical processes, where sampling intensity is extraordinarily high to meet existing methodologies. In the future, the community will need to determine which data streams truly drive confidence in results, and where simplification may be possible without sacrificing rigor. For now, the priority is to build the evidence base that will allow those distinctions to be made. Over time, agreeing on which parameters are most relevant for each pathway—and standardizing how they are measured—will enable scaling and comparability across projects. Participants also emphasized that consistent LCA accounting methods are essential to ensure results are comparable across registries and regions.
• Uncertainty at All Scales of Analysis: Both life-cycle assessment and integrated assessment models must incorporate uncertainty ranges explicitly. Uncertainty should be treated as a first-class element of MRV—quantified, disclosed, and explicitly factored into crediting—so buyers understand the level of confidence they are purchasing. At the same time, participants emphasized that projects must continue to move forward, because real-world deployment is how uncertainty is reduced. Learning through implementation and data collection is essential to improving methods over time.
• Scaling and MRV Efficiency: MRV for open systems is both a scientific and an engineering challenge. Scientific questions remain around what to measure and how to capture variability across sites and timescales. At the same time, scaling will depend on better engineering of data systems. Computational tools—such as application programming interfaces (APIs) that connect registries to verifiers; extract-transform-load (ETL) pipelines that automate data cleaning and integration; and common data architectures—are now bigger bottlenecks than physical sensing. Streamlining data flow and verification through automation can dramatically reduce costs and improve consistency. As projects scale, the per-ton cost of MRV should fall, and rules should evolve alongside these technological advances.
• Buyers, Registries, and the Future of Transparency: Buyers have played a catalytic role in the early stages of the CDR market, helping set expectations for data sharing and clear communication. However, buyers are not well positioned to define the long-term rules of the market. Their incentives may diverge from those of suppliers, registries, and civil society, particularly as verification frameworks mature. In practice, registries in this emerging market often serve multiple functions—developing and maintaining methodologies, coordinating third-party validation and verification, and ensuring the transparent tracking of issued credits. These integrated roles position them at the center of efforts to build trust and accountability. Suppliers, meanwhile, must balance transparency with the need to attract capital and talent to scale durable, low-cost removal. Over time, registries—and eventually an independent standards body — will need to take the lead in establishing and enforcing consistent transparency requirements across the market.

Issues Still on the Table

• What to Measure, and Where: Open systems remain scientifically complex, and many fundamental questions persist about their overall effectiveness. While measurement capabilities are advancing rapidly, the core challenge is that we are still prioritizing which processes are most fundamental to durable carbon removal, based on the best available science—an understanding that will continue to evolve with ongoing research. In enhanced rock weathering, for instance, the science must account not only for carbon removed in soils but also for what is retained in transport through hydrological pathways into rivers and oceans. For ocean alkalinity enhancement, uncertainties remain around biological and geochemical feedbacks that could alter removal efficiency. These scientific gaps make it difficult to define the right indicators for commercial MRV. Designing scalable, simple, and credible MRV systems will therefore depend on advancing our understanding of these coupled Earth system processes and developing practical methods to measure them at relevant scales.
• Stacking vs. Double Counting: Participants distinguished between stacking appropriate claims (e.g., a company credit and a national credit for the same activity) and prohibited double counting that inflates environmental impact. Clearer rules are needed to prevent confusion.
• Global vs. Regional Standards: While global harmonization is desirable for trading and trust, rushing to align methods while also accommodating regions with varying capacity could bake in suboptimal rules. Measurement techniques may justifiably differ by context, but the burden of proof—the level of evidence required to demonstrate removal and quantify uncertainty—should remain consistent across regions and methodologies.

Looking Ahead

What began as a meeting to “map the questions” ended up demonstrating how much agreement already exists and pointing to paths forward. Participants coalesced around shared priorities: extending rigorous standards for open systems, expanding transparent datasets, embedding uncertainty into models at all scales of analysis, and leveraging buyer influence to push for transparency.

The next steps will include a jointly authored perspective piece, open data-sharing initiatives, and a follow-up convening in 2026 to track progress. The message was clear: we are not starting from scratch. By building on shared principles of transparency, consistent accounting methods, robust data, explicit uncertainty, and buyer-driven accountability, the MRV community can ensure that open-system carbon removal delivers the real and durable climate benefits the world urgently needs.

Authors:

Jen Wilcox¹²³, Roger Aines⁴, Giana Amador⁵, Candelaria Bergero⁶, Brian Buma⁷, Hao Cai⁸, Rodrigo Castro⁹, Greg Cooney¹, Audrey Denvir², Susan Fancy¹⁰, Steve Hamburg⁷, Tim Hansen¹¹, Zeke Hausfather¹², Jon Hawkings¹, Jing He³, Ella Holme³, Priyanka Hooghan¹³, Rory Jacobson¹⁴, Rudy Kahsar¹⁵, Anu Khan¹⁶, Ashwin Kishen¹⁷, Wenqin Li⁴, Abby Lunstrum¹, Kimberley Mayfield⁴, Samantha McBride¹, Peter Minor¹⁸, Likhwa Ndlovu¹, Simon Pang⁴, Shrey Patel¹, Edward Sanders¹⁹, Rebecca Sanders-DeMott²⁰, Michael Shell³, Lucia Simonelli¹⁶, Aline Uwase¹, Aaron Weiskittel²¹, Adam Wolf²²

¹ University of Pennsylvania

² World Resources Institute

³ Isometric

⁴ Lawrence Livermore National Lab

⁵ Carbon Removal Alliance

⁶ University of Wisconsin

⁷ Environmental Defense Fund

⁸ Argonne National Lab

⁹ Puro

¹⁰ University of Michigan Global CO2 Initiative

¹¹ 350 Solutions

¹² Stripe

¹³ Carbon to Sea

¹⁴ Carbon Direct

¹⁵ RMI

¹⁶ Carbon Removal Standards Initiative

¹⁷ Terradot

¹⁸ Absolute Climate

¹⁹ Equatic

²⁰ Clean Air Task Force

²¹ University of Maine

²² Eion Carbon