Two Sides of Carbon Removal: Engineered or Nature-Based?

Two Sides of Carbon Removal: Engineered or Nature-Based?

Carbon removal (or carbon dioxide removal - CDR) is increasingly discussed in climate strategies. IPCC scenarios show that achieving the 1.5°C target requires carbon removal alongside emission reductions. As the topic becomes more popular, concepts also get mixed up.

On one side, there are nature-based approaches. On the other, engineering-based approaches. Both are based on the idea of "pulling carbon from the atmosphere and storing it for a long time." The difference lies in how this is done and how risks are managed.

Difference between carbon removal and carbon reduction

Let's first clarify the basic distinction. Carbon reduction (emission reduction) is prevented emissions. For example, replacing fossil fuels with renewable energy. Carbon removal is the extraction and storage of CO2 that already exists in the atmosphere.

This distinction is important because they serve different roles. Reduction is needed to stop emissions. Removal is needed to offset residual emissions that cannot be reduced and to clean up past accumulation.

Nature-based carbon removal

Nature-based approaches use ecosystems' carbon capture capacity. CO2 is captured through photosynthesis and stored in biomass or soil.

Key methods

Afforestation and forest restoration: Creating new forests or restoring degraded forests. Trees store carbon as they grow. It is widespread and relatively low-cost.

Soil carbon: Increasing carbon accumulation in soil through agricultural practices (cover crops, minimum tillage, organic matter addition). This is an important opportunity for the agricultural sector.

Blue carbon: Carbon capture capacity of coastal ecosystems such as mangrove forests, seagrasses, and salt marshes. These ecosystems can store more carbon per unit area than terrestrial forests.

Advantages

• Relatively low cost (in the range of 5-50 USD per ton)
• Biodiversity conservation and enhancement
• Community livelihoods and social benefits
• Existing knowledge and experience base
• Fast scaling potential

Risks and challenges

Permanence uncertainty: Stored carbon can return to the atmosphere through forest fires, disease, pests, or land use change. There is an expectation of permanence in the 10-100 year range, but no guarantee.

Monitoring and verification challenges: Carbon accumulation is measured indirectly. A combination of satellite imagery, field samples, and modeling is used. The margin of uncertainty can be high.

Leakage risk: While conservation is done in one area, deforestation may shift to another area. Net impact is reduced.

Additionality question: Would the trees have been planted even without the project? This question is difficult to answer.

Engineered carbon removal

Engineering-based approaches capture carbon with technological systems and store it long-term. Storage typically occurs in geological formations or stable mineral forms.

Key methods

Direct Air Capture (DAC): Capturing CO2 directly from the atmosphere. CO2 is separated from the air flow using chemical or physical methods. Captured CO2 is injected into geological formations or converted into products.

Biochar: Converting biomass to a stable carbon form by heating in an oxygen-free environment (pyrolysis). Biochar can remain in soil for hundreds of years and can improve soil fertility.

Enhanced weathering: Grinding silicate rocks (like basite) and spreading them on agricultural land. This accelerates the natural weathering process. It reacts with CO2 to form stable carbonate forms.

Bioenergy with carbon capture and storage (BECCS): Capturing CO2 produced during biomass combustion and storing it geologically.

Ocean-based methods: Approaches such as increasing ocean alkalinity or ocean-based biomass production are still in the research stage.

Advantages

• High permanence (100-10,000 years, depending on method)
• Measurability and verifiability
• Independence from land use (for DAC)
• Geographic flexibility

Risks and challenges

High cost: 300-1000+ USD per ton for DAC. Cost is expected to decrease as technology matures, but it will take time.

Energy intensity: DAC requires significant amounts of energy. If the energy is not clean, net carbon benefit decreases.

Scale limitations: Current capacities are very small. Reaching gigaton scale will take years.

Comparison criteria

Permanence (durability)

• Nature-based: 10-100 years (condition-dependent, reversal risk exists)
• Engineered: 100-10,000 years (with geological storage)

MRV (monitoring, reporting, verification)

• Nature-based: Combination of satellite, field measurement, modeling. Uncertainty can be high.
• Engineered: Direct measurement, sensors, mass balance. Uncertainty is low.

Cost

• Nature-based: In the range of 5-50 USD per ton
• Engineered: In the range of 100-1000+ USD per ton

Co-benefits

• Nature-based: Biodiversity, water regulation, livelihoods
• Engineered: Limited co-benefits (except biochar)

Portfolio approach

There is no single right answer. Many experts and organizations recommend a portfolio approach:

• Achieve scale with nature-based solutions in the short term
• Achieve permanence with engineering-based solutions in the long term
• Combine different methods for risk diversification

The choice should align with the company's climate strategy, risk appetite, budget, and stakeholder expectations.

Oxford Principles and corporate claim guidance

The Oxford Principles for Net Zero Aligned Carbon Offsetting provides fundamental principles for high-quality carbon removal:

1. Prioritize reduction: First reduce emissions, then use removal as an offset
2. Shift to permanence: Move portfolio from short-term storage to long-term storage
3. Environmental integrity: Demand mechanisms that prevent reversal and strong MRV
4. Support net zero transition: Contribute to scaling removal capacity

Things to consider in corporate claims: "Carbon neutral" or "net zero" claims are directly related to the quality of credits used. These claims become more credible when real carbon removal, not just emission reduction, is used. Companies should clearly state whether the credits they use are removal or avoidance.

Purchasing criteria

When purchasing carbon removal credits, pay attention to:

1. Methodology: Which standard was used? (Verra, Gold Standard, Puro.earth, etc.)
2. Permanence: How is storage duration and reversal risk managed?
3. Additionality: Would the project have happened without credit revenue?
4. MRV: How is monitoring and verification done?
5. Third-party verification: Is there independent verification?

Conclusion

Carbon removal is not a problem that can be solved with a single method. Nature and engineering-based approaches complement each other. Nature-based solutions can scale today and offer co-benefits but carry permanence risk. Engineering-based solutions provide high permanence but are costly and still small-scale.

What matters is making informed choices knowing the strengths and weaknesses of each method and managing risks with a portfolio approach.