Glossary

Defining the terms that appear regularly in our work

Clarity is crucial in a jargon-heavy industry like carbon removal. This glossary aims to provide a shared set of definitions for the language we use. Many of these definitions are Isometric’s own. Others are based on the CDR Primer's glossary, which reflects the consensus of dozens of industry experts. Of these, some have been simplified for ease of reference. Symbols below each definition indicate their source. Where we have adopted a definition from another source, we specify this explicitly..

Activity

The steps of a supplier’s removal process that result in carbon fluxes. The carbon flux associated with an activity is a component of the supplier’s protocol.

Additionality

An evaluation of the likelihood that an intervention—for example, a CDR project—causes a climate benefit above and beyond what would have happened in a no-intervention baseline scenario.

Anthropogenic carbon emissions

The increase in carbon dioxide from storage reservoirs to the atmosphere that results from human activities, such as burning fossil fuels or deforestation.

Avoided emissions

Greenhouse gas emissions that would occur in a no-intervention baseline scenario, but which do not occur as a result of intervention.

Baseline

A set of data describing pre-intervention or control conditions to be used as a reference scenario for comparison.

Buyer

An entity (usually a corporation, but can also be an individual or a government entity) that purchases CDR, often with the purpose of retiring CDR credits to make a carbon neutral or net-negative claim.

Carbon accounting

The act of quantifying carbon dioxide and other greenhouse gas emissions throughout a process or product's life cycle, or those associated with an individual, organization, company or polity.

Carbon credit

A uniquely identifiable certificate issued by a registry such as Isometric that gives the owner of the credit the right to account for 1 net metric tonne of verified carbon dioxide equivalent removal.

Carbon dioxide removal (CDR)

Activities that remove carbon dioxide from the atmosphere and store it in geological, terrestrial or ocean reservoirs—or in durable products. CDR includes the enhancement of biological or geochemical sinks and direct air capture (DAC) and storage, but excludes natural carbon dioxide uptake not directly caused by human intervention. Isometric also refers to CDR as “carbon removal.”

Carbon flux

The amount of carbon exchanged between two or more carbon reservoirs over a period of time.

Carbon intensity

The amount of carbon or carbon-equivalent emissions related to the unit production of a service or good, including individual activities (such as transportation) for a given process. Carbon intensity for a good is typically measured over its entire life cycle. Carbon intensity can also be referred to as an emissions intensity or an emissions factor.

Carbon reservoir

A physical place or system in which carbon is stored, such as in the biosphere, atmosphere or oceans. Two or more carbon reservoirs can exchange carbon fluxes.

Carbon uptake

The flux of carbon from the atmosphere to another carbon reservoir, such as the biosphere or oceans.

Component

Each of the carbon fluxes for a given CDR process that, together, form the basis of a modular protocol. Carbon fluxes associated with activities, counterfactuals and losses are all considered components.

Counterfactual

A quantification of what would have happened in the absence of a particular intervention, i.e. assuming the baseline conditions. In CDR, this involves both the potential emissions that would have occurred if a supplier did not engage in their CDR process, as well as those that occurred because a supplier's CDR process changed the existing supply and demand dynamics in a given sector.

Delivery

The outcome of a supplier apportioning removals into orders to fulfill their buyers’ purchases. A removal can only be delivered after it has been verified.

Direct emissions

Emissions that are produced by a specific CDR process and are directly controllable.

Durability

The amount of time the carbon removed by an intervention—for example, a CDR project—is expected to reside in a given carbon reservoir, taking into account both physical risks and socioeconomic constructs such as contracts to protect the reservoir in question. The word “permanence” is often used to describe removals of high durability.

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Greenhouse gas (GHG)

Those gaseous constituents of the atmosphere, both natural and anthropogenic (human-caused), that absorb and emit radiation at specific wavelengths within the spectrum of terrestrial radiation emitted by the Earth’s surface, by the atmosphere itself and by clouds. This property causes the greenhouse effect, whereby heat is trapped in Earth’s atmosphere.

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Life cycle analysis (LCA)

An analysis of the balance of positive and negative emissions associated with a certain process, which includes all of the flows of carbon dioxide and other greenhouse gases, along with other environmental or social impacts of concern. This is also referred to as “life cycle assessment”.

Loss

A type of component that encompasses emissions of previously removed carbon in the removal process. These can occur both after carbon has been removed but before it has been durably stored due to environmental feedbacks, and after storage due to leakage from the reservoir.

Marketplace

An entity that purchases CDR credits for the purpose of selling them to other buyers rather than retiring them.

Monitoring

The measurement of a CDR process and the ongoing impacts of its emissions, specifically with an eye toward whether the removed carbon stays safely and durably stored away.

Negative emissions

When a sink—created or enhanced by humans—removes greenhouse gases from the atmosphere.

Net-negative emissions

When more greenhouse gases are removed from the atmosphere than are emitted into it, by a specific entity or society as a whole, over a given time period.

Net-zero emissions

When the same amount of greenhouse gases are removed from the atmosphere than are emitted into it, by a specific entity or society as a whole, over a given time period.

Order

A set number of tonnes that a buyer purchases from a supplier in a given contract.

Pathway

A collection of CDR processes that have removal and storage mechanisms in common. For instance, Isometric considers enhanced rock weathering to be a pathway. Notably, no two suppliers will perform removal and storage using precisely the same process, due to differences in activities.

Process

The approach that a certain CDR company uses to perform CDR, which is made up of actions by the supplier and their supply chain to remove carbon dioxide. The process describes the supplier activities that have associated carbon fluxes.

Protocol

How to quantitatively assess the net amount of carbon dioxide equivalent removed by a process. In Isometric’s work, a protocol is specific to a supplier’s process and made of modules representing the fluxes involved in the CDR process. A protocol measures the full carbon impact of a process against the baseline of it not occurring.

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Registry

A database that holds information on verifiedCDR based on protocols. Registries issue credits and track their ownership and retirement.

Reporting

A detailed breakdown of a CDR project, which includes both net negativity and durability. Other values such as uncertainty, wider ecosystem impacts and the project’s efficiency might be included as well.

Retirement

The act of confirming the final ownership of a given credit. The beneficiary of this act is the ultimate owner of the tonne of removal and the sole claimant as to its attributes for the purpose of carbon accounting.

Sink

Any process, activity or mechanism that removes a greenhouse gas, a precursor to a greenhouse gas or an aerosol from the atmosphere.

Storage

The addition of carbon dioxide removed from the atmosphere to a reservoir, which serves as its ultimate destination. This is also referred to as “sequestration”.

Supplier

An entity that removes carbon dioxide from the atmosphere so that it can be stored durably and sells this service to buyers.

Tonnes

Metric tons—equivalent to 1,000 kilograms—which is the standard unit for CDR.

Uncertainty

A lack of knowledge of the exact amount of carbon dioxide removed by a particular process, due to factors such as our inability to precisely measure certain physical phenomena or simplified assumptions made in models or life cycle assessments. Uncertainty may be quantified using probability distributions, confidence intervals or variance estimates.

Verification

A process for evaluating a statement of historical data and information to determine if the statement is materially correct and conforms to criteria.
‍ISO 14064-2:2019

Verified removal

The outcome of conducting CDR that follows a specific process, and then of having the removal claim successfully and independently verified.

Voluntary carbon market

Avoided or removed carbon dioxide emissions (quantified as credits) that are exchanged through marketplaces that are not created or utilized for policy compliance. Individuals and companies procure carbon credits through these markets on an entirely voluntary basis. Traditionally, the VCM is made up mostly of avoidance-based credits (also known as “offsets”). The number of removal-based credits in the VCM is increasing as the CDR industry grows.