Glossary

 

Carbon dioxide removal is becoming an important part of climate policy, carbon markets, and net-zero discussions. This glossary is a simple guide to the key concepts behind carbon dioxide removal. It is designed for readers who want to understand the basic vocabulary before reading reports, policy documents, or market updates on CDR. This page will be updated regularly as new terms, technologies, and policy discussions emerge.

Core Concepts

Carbon Dioxide Removal (CDR)

Human activities that remove CO₂ from the atmosphere and store it durably in geological, terrestrial, ocean reservoirs, or products.

Emissions Reductions

Actions that reduce new greenhouse gas emissions released into the atmosphere. CDR does not replace emissions reductions; it complements them.

Net Zero CO₂ Emissions

A state in which CO₂ emissions are balanced by CO₂ removals, so net CO₂ emissions equal zero.

Gross CO₂ Emissions

The total amount of CO₂ released to the atmosphere before subtracting removals.

Gross CO₂ Removals

The total amount of CO₂ removed from the atmosphere before being netted against emissions.

Residual Emissions

Emissions that remain difficult to eliminate even after deep decarbonization. These are typically balanced by carbon dioxide removal at net zero.

Paris Temperature Goal

The long-term goal of the Paris Agreement to hold global warming to well below 2°C and pursue efforts to limit it to 1.5°C.

Conventional CDR

More established and widely deployed CDR methods, often related to forests, land, soils, and wood products.

Novel CDR

Emerging CDR approaches that are currently deployed at smaller scales and are generally less mature, such as BECCS, DACCS, biochar, and enhanced weathering.

CDR Gap

The gap between the amount of CDR currently pledged or deployed and the amount needed in Paris-compatible climate scenarios.

Durability

The ability of stored carbon to remain out of the atmosphere over time. The more durable the storage, the more reliable the climate benefit.

Additionality

Whether a removal or reduction happens only because of a specific policy, project, or carbon credit mechanism, rather than occurring anyway.

Monitoring, Reporting and Verification (MRV)

The system used to measure, document, and independently verify carbon removals or emissions reductions. MRV is essential for credibility and quality assurance.

Carbon Credit

A tradable certificate that usually represents one tonne of CO₂ or CO₂-equivalent reduced, avoided, or removed.

Offset

A reduction, avoided emission, or carbon removal used to compensate for emissions produced elsewhere.

Carbon Capture and Storage (CCS)

The process of capturing CO₂, compressing it, transporting it, and storing it in geological formations. When the CO₂ comes from fossil sources, CCS is generally considered emissions reduction rather than CDR.

Carbon Capture and Utilisation (CCU)

The capture of CO₂ for use in products. It only counts as carbon dioxide removal if the CO₂ comes from the atmosphere and is stored durably.

Overshoot Pathway

A climate pathway in which global warming temporarily exceeds a target such as 1.5°C and later falls back below it through stronger mitigation and carbon removal.

CDR Methods

Direct Air Capture (DAC)

A chemical process that captures CO₂ directly from ambient air. The captured CO₂ can then be stored or used in products.

Direct Air Carbon Capture and Storage (DACCS)

A CDR method that captures CO₂ directly from the air and stores it permanently in geological formations.

Bioenergy with Carbon Capture and Storage (BECCS)

A method that captures biogenic CO₂ from bioenergy processes and stores it geologically.

Biochar

A stable, carbon-rich material produced by heating biomass in low-oxygen conditions. It can improve soils and store carbon for long periods.

Enhanced Weathering

A method that accelerates the natural weathering of silicate or carbonate rocks to increase CO₂ removal from the atmosphere.

Afforestation

The establishment of forests on land that was not previously forested, increasing carbon storage in vegetation and soils.

Reforestation

The re-establishment of forests on land that was previously forested but later cleared or degraded.

Forest Management

The management of existing forests in ways that increase long-term average carbon stocks.

Soil Carbon Sequestration

The storage of carbon in soils through changes in agricultural or land management practices that increase soil organic carbon.

Peatland and Coastal Wetland Restoration

The restoration of peatlands, salt marshes, mangroves, and seagrass ecosystems to increase or protect long-term carbon storage.

Durable Wood Products

Long-lived wood products such as lumber, panels, and engineered wood that store carbon outside the forest for extended periods.

Mineral Products

Solid carbonate materials made using atmospheric CO₂, including products such as aggregates, asphalt, cement, and concrete.

Direct Ocean Carbon Capture and Storage (DOCCS)

A process that captures CO₂ directly from seawater and stores it geologically. To count as CDR, it must increase ocean uptake of atmospheric CO₂.

Alkalinity Enhancement of Water Bodies

The addition of alkaline minerals or their dissolved products to oceans, rivers, or lakes to enhance CO₂ uptake and storage.

Biomass Burial

The burial of biomass in soils, disused mines, or other land-based sites to extend the storage of carbon.

Biomass Sinking

The sinking of terrestrial or marine biomass into the ocean. To count as CDR, the carbon must reach deep ocean storage with durable sequestration potential.

Ocean Fertilisation

The addition of nutrients to the upper ocean to stimulate biological activity and promote additional CO₂ uptake and sequestration.

Reference
[1] Singleton, S. & Edwards, M. The State of Carbon Dioxide Removal - 3rd Edition (2026). https://doi.org/10.17605/OSF.IO/ZRD65 (2026) doi: 10.17605/OSF.IO/ZRD65.