What Makes Carbon Removal Durable? The Science Behind Durable CDR Projects

The climate crisis demands more than just emissions reductions. Even as companies plan toward their net-zero target year, residual GHG emissions will persist across nearly every sector.

This reality puts durable carbon removal into the spotlight as a critical tool for achieving net zero and, eventually, a future where we can reverse decades of emissions.

But not all carbon removal technologies deliver the same long-term climate impact. The key difference lies in durability (often used interchangeable with ‘permanence’) — how long removed CO2 stays out of the environment and how confident we can be in that claim. 

For companies navigating the voluntary carbon market and aligning with science based targets initiative (SBTi) guidelines, understanding durability is essential for credible climate action.

Why Durability Is the North Star for Carbon Removal

Carbon removal serves two climate functions.

First, it neutralizes stubborn residual emissions that remain after decarbonization efforts. The vast majority of companies contribute to unavoidable emissions via activities like cement production, aviation, or agriculture that require genuine removal for net zero alignment.

Second, durable removals enable the transition from net zero to net-negative emissions. This phase is necessary to limit global warming, and eventually, draw down atmospheric CO2 concentrations that have accumulated over decades of consistent industrial activity.

But here's the thing: durability in carbon removal is necessary to achieve these goals. Otherwise, the removed greenhouse gas emissions will leak back into the atmosphere and re-contribute to peak warming.

For corporate buyers, durability translates into two straightforward questions: "How long will removed CO2 stay out of the atmosphere?" and "How confident can we be in that claim?" These questions connect directly to business priorities like net zero alignment, auditability, and reputational resilience.

Tools like Sylvera help corporate buyers answer these questions with confidence, leading to more reliable carbon credits that deliver lasting results, not temporary fixes.

What We Mean by "Durable CDR"

Durability exists on a spectrum; it’s not as binary permanent or temporary storage.

Generally speaking, durable carbon removal refers to storage lasting centuries to millennia, while shorter-lived approaches store carbon for years to decades.

This distinction matters because different storage timescales serve different purposes. For example, durable solutions with permanent geologic storage are ideal for long-term climate goals. Meanwhile, shorter-lived approaches like nature based solutions can provide valuable interim benefits while companies transition operations and scale up access to more permanent storage strategies.

The key lies in risk-adjusted thinking. Even within durable pathways, storage confidence varies based on site-specific conditions, monitoring capabilities, and governance structures. For example, direct air carbon capture and storage (DACCS) plants offer millennial-scale storage potential, but actual durability depends on a variety of factors, from plant location to methodology.

The Durability Ladder: Comparing Storage Pathways

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Which storage pathway is the most durable? More importantly, which projects produce the right carbon offsets for your organization? Here, we compare popular carbon removal options.

• Geologic storage through direct air capture or BECCS offers the highest durability when properly sited and monitored. CO2 injected into suitable subsurface formations can remain stored for millennia. The primary risks center on location and long-term monitoring obligations.
• Mineralization and enhanced weathering approaches chemically bind CO2 into stable carbonate minerals. Once formed, these carbonates offer exceptional permanence. However, the kinetics of these reactions vary by context, and measurement approaches continue to evolve.
• Biochar creates relatively stable carbon pools when high-quality feedstock undergoes proper pyrolysis and is applied to suitable soils. Durability depends heavily on feedstock selection, pyrolysis conditions, and soil characteristics. But well-designed biochar systems can store carbon for centuries while delivering valuable co-benefits, such as enhanced soil health.
• Biomass pools, like forests and agricultural soils, can be valuable in the fight against climate change. However, they face shorter average residence times and require careful accounting for reversal risks. They also need buffer mechanisms to maintain credibility over time.

Five Pillars that Make CDR Durable (and Investable)

How do you evaluate durability before investing in carbon credits? Take a look at the five pillars below, which determine whether carbon removal projects can deliver on their durability promises.

1. Storage Physics and Site Integrity

The chosen storage mechanism drives inherent reversal risk.

Geologic storage relies on caprock integrity—impermeable rock layers that prevent CO2 migration back to the surface. Enhanced rock weathering depends on reaction kinetics and mineral stability. Product-bound carbon storage requires an understanding of degradation pathways and end-of-life management.

Corporate buyers should look for projects that demonstrate thorough site characterization, appropriate storage mechanism selection, and strong integrity assessment protocols. This due diligence should happen before project implementation, not after carbon credits hit the market.

Proper due diligence for emerging projects in this space is necessary, such as with Sylvera's Pre-Issuance Ratings. Use the tool to learn about a project's expected rating at issuance, how and when credits will be delivered, and revenue potential.

2. Measurement, Reporting, and Verification (MRV) That Stands Up to Scrutiny

Robust MRV systems provide the foundation for credible durability claims.

Direct measurement approaches generally offer higher confidence than modeled inference, though both can play an important role depending on the pathway and context.

For geologic storage, use comprehensive monitoring networks that detect potential leakage and verify injection volumes. For enhanced rock weathering, track reaction progress and account for natural variability.

For nature-based removal approaches, there’s the need for high-fidelity biomass data that avoids systematic bias. (Note: Sylvera's extensive use of terrestrial LiDAR technology, and the enormous amount of ground-truth data we've collected, enables us to give highly accurate Ratings for nature-based projects.)

Regardless of pathway, uncertainty treatment is crucial. Projects should explicitly quantify and communicate uncertainty ranges rather than presenting point estimates as definitive facts. Leakage accounting is also important, as it ensures claimed removals represent real atmospheric benefits.

3. Risk Management and Reversal Coverage

Even durable pathways face reversal risk over long time horizons. As such, effective risk management combines multiple solutions based on pathway-specific needs and risk profiles.

Buffer pools work well for nature-based approaches where statistical analysis can estimate expected reversal rates across project portfolios. Insurance products can cover specific risks like geological events or operational failures. Contractual guarantees shift reversal liability to project developers or operators. And long-term liability assignment keeps responsible parties accountable.

The trick is to match risk management tools to actual risk drivers, rather than applying one-size-fits-all approaches across diverse carbon removal technologies.

4. Governance and Counterparty Resilience

Durable storage requires durable institutions.

Operator maturity, financial resilience, and operational capabilities determine whether projects can maintain performance across decades—or centuries—of monitoring and management.

This includes adequate funding mechanisms for operations and maintenance throughout the storage lifetime, clear monitoring obligations with enforcement mechanisms, and financial reserves or escrow arrangements that ensure continuity, even if the original operator exits the market.

Companies should evaluate track records, financial health, delivery milestones, and alignment with recognized standards when selecting carbon removal partners. Strong governance doesn't ensure success, but weak governance all but guarantees future problems.

5. Economics and Pathway to Scale

Durability commands a price premium in the voluntary carbon market, reflecting both higher technical complexity and lower reversal risk. Understanding cost curves, resource constraints, and scalability factors helps companies plan procurement strategies that balance durability goals and budgets.

For instance, energy and water requirements vary dramatically across carbon removal technologies. And siting constraints limit the scalability of different approaches. These factors influence both near-term availability and long-term cost trajectories for durable carbon removal projects.

Your company should consider how durability premiums evolve over time as technologies mature, economies of scale develop, and policy support expands. Early investments in higher-cost durable solutions can secure access to limited supply, in addition to supporting market developments.

Accounting for Durability Over Time

Traditional carbon accounting strategies treat all removals equally, regardless of storage duration.

This approach oversimplifies the climate value delivered by different pathways and can lead to poor investment decisions. You can avoid this by adjusting your accounting strategy for each project.

Time-adjusted accounting approaches explicitly factor storage duration into credit valuation. For example, removing one ton of CO2 for 20 years delivers different climate value than removing one ton of CO2 for 1,000 years. Various methodologies exist (for example in biochar, see here) for quantifying these differences, from simple discount factors to complex modeling of atmospheric residence times.

Stacking concepts allow companies to combine credits from different pathways while explicitly accounting for their varying durability profiles. This enables said companies to build portfolios that balances immediate needs (covered by shorter-lived approaches) with long-term requirements (addressed through durable solutions). That way, the needs of today and tomorrow are met.

Portfolio Design: Blending Durability, Cost, and Co-Benefits

Most companies benefit from diversified carbon removal portfolios that blend high-durability approaches with shorter-term options. This strategy balances several considerations:

• Risk management: Every portfolio approach has risks. Diversification across pathways, geographies, and operators reduces them while maintaining overall portfolio durability.
• Cost optimization: Durable solutions are often more expensive, especially during the early market development phase. Blending approaches allows companies to meet budget constraints while still investing in permanent solutions that lower net emissions and improve the environment.
• Co-benefits alignment: Different pathways deliver different co-benefits. Examples include biodiversity protection, soil health improvement, or local economic development. Portfolio construction can optimize for these values alongside carbon removal durability.
• Timing flexibility: Markets for different carbon removal technologies mature at different rates. Diversified portfolios enable companies to access available supply while supporting not-yet-mainstream approaches that have longer-term potential.

Sylvera's Market Intelligence helps inform these portfolio decisions by providing insights into price discovery, forward curves, and supply availability across different pathways and time horizons.

What Good Due Diligence Looks Like (A Checklist)

Effective due diligence for durable carbon removal operates at three levels:

Project-level assessment:

• The storage mechanism is appropriate and validated for this specific site
• There is a comprehensive MRV plan that accounts for project uncertainties
• There is long-term operations and maintenance (O&M) funding and planning
• There are risk management tools and sufficient reversal coverage in place
• Liability is clearly spelled out for the full duration of the storage period
• The project aligns with recognized standards and certification programs

Counterparty evaluation:

• The developer has a strong track record
• The developer demonstrates financial resilience
• The developer consistently meets delivery milestones
• The developer is transparent in reporting and communication

Jurisdictional and policy analysis:

• The project aligns with local regulations
• The project helps the company prepare for adhering to Article 6

This comprehensive approach to due diligence will help your company identify the right projects and partners, and produce durable carbon removal credits at scale.

Support Quality CDR Projects

The climate crisis demands immediate action and long-term solutions.

Durable CDR projects might take more time and money to build, but they offer a realistic path to a net-zero future, and have the potential to scale. The question is, how do you assess durability?

As stated above, you need to move beyond simplistic ton-for-ton thinking and toward a nuanced evaluation of storage mechanisms, risk management approaches, and counterparty capabilities.

By combining strong due diligence with transparent MRV and market intelligence, you can make better carbon investments that improve your company's financial position and combat global warming.

Sylvera has the tools you need to succeed in the Durable CDR market. Our Pre-Issuance Ratings use scientific research to help you identify quality projects to support, while our Ratings help you pinpoint high-integrity credits that have already been issued. Then, our Market Intelligence helps time purchases to make the most of your budget. Book a demo of Sylvera today to learn more.