Tabitha Whiting
Tabitha WhitingContent Marketer
Carbon offsetting and removal: a glossary of terms
Carbon offsetting and removal: a glossary of terms
There's lots of terminology to get your head around when it comes to climate change and carbon offsetting – so we've put together this carbon offsetting and removal glossary to help.
April 11, 2022


Carbon offsetting and removal can be a complex topic – including the language used.

What's the difference between carbon neutral and net zero? What does permanence mean in the context of carbon offsetting? And why the hell do we measure carbon emissions as tCO2e? There's a lot to get your head around, but language should never be a barrier in your climate journey – so we've put together a glossary of terms to bring all that terminology into one convenient place.

We'd recommend bookmarking this one to keep it safe for when you need it again!


Additionality: a project has resulted in emissions reductions or removals in addition to what would have occurred in the absence of the project. For more detail, go to our blog: Additionality in carbon offsetting, explained.

Afforestation: planting new forests on land which has historically not been forest.


Biochar: a carbon-rich material similar to charcoal, but produced by a specific method of heating biomass waste in a low oxygen environment. It is then applied to soil where the carbon will be safely stored, whilst also improving the quality of the soil for plant growth.

Bio-oil sequestration: waste biomass (typically from agriculture) is converted into a stable, carbon-rich liquid known as 'bio-oil'. The bio-oil is then injected deep underground, permanently storing the carbon.

Blue carbon: the carbon captured by living organisms in coastal (e.g., mangroves, salt marshes, seagrasses) and marine ecosystems, stored in biomass and sediments.


Carbon capture: a process in which CO2 from industrial and energy-related sources is separated (captured), conditioned, and compressed. It is then stored safely, known as carbon capture and storage, or used to create products such as sparkling water or building materials, known as carbon capture and usage.

Carbon credit: a unit used to represent emissions removal or reduction/avoidance, sold by carbon projects to carbon buyers as a way to compensate for emissions produced elsewhere. 1 carbon credit is equal to 1 tonne of CO2e reduction or removal.

Carbon drawdown: used as a synonym for carbon removal or CDR.

Carbon emissions: carbon dioxide that enters the atmosphere. This happens naturally through biological processes like respiration but are also caused by human activities, especially the burning of fossil fuels to generate energy. Carbon dioxide is one of several greenhouse gases that contribute to the greenhouse effect by absorbing infrared radiation, trapping heat and causing global warming.

Carbon footprint: the total amount of greenhouse gas (GHG) emissions produced by the actions of an individual, product, organisation or country, used as a measure of their climate change impact.

Carbon market: a market where carbon credits can be bought and sold, creating a system where countries, businesses etc can be financially incentivised to reduce their carbon emissions through putting emission limits in place.

Carbon negative: a state in which a company, individual, or country is responsible for a negative amount of carbon emissions i.e. less than zero. This means that they are offsetting more carbon emissions than they create via carbon removal or emissions avoidance projects.

Carbon neutral: where the total amount of greenhouse gas (GHG) emissions produced is offset in its entirety by either carbon removal or emissions avoidance, offsetting the impact. The term is usually used in association with products or businesses. NB: this is different to net zero, where offsets need to actively remove carbon from the atmosphere.

Carbon offset projects: projects designed with the purpose of carbon removal or emissions reduction. They use carbon offset credits as a financing mechanism: once verified by a carbon standard the project issues carbon credits equivalent to the amount of carbon the project will remove or avoid, which can then be purchased by individuals or businesses who want to offset their own emissions.

Carbon offsetting: compensating for carbon emissions by financing projects that claim to make an equivalent reduction in carbon emissions. 

Carbon registry: online systems to track carbon credits being issued to project developers and purchased by buyers. This includes retiring credits once purchased to avoid the risk of double counting; a certificate will usually be sent to the buyer as proof of retirement.

Carbon removal or Carbon Dioxide Removal (CDR): physically removing existing carbon from the atmosphere and storing it. This happens in nature (forests, soils, oceans) but it can also be achieved by technological solutions e.g. Direct Air Capture. 

Carbon sink: a reservoir that absorbs and stores carbon emissions. Usually refers to natural environments such as forests, oceans, and soil.

Carbon standard: there’s currently no government set standard for projects in the voluntary carbon market, so standards are being set by trusted, independent standards. The major such as Gold Standard, Verified Carbon Standard (Verra), and Puro.Earth.

Co-benefits: important positive implications of carbon offset projects that go beyond carbon, to have other social and environmental impacts e.g. biodiversity or job creation.

Compliance market: a carbon marketplace governed by law, stating that companies (typically high-emitters like airlines and oil and gas) have a cap on the amount of greenhouse gases they are allowed to emit each year, and have to buy carbon credits if they go over this.


Deforestation: the act of clearing a forest. Typically done to harvest wood as a resource, and/or to clear land for some other economic use e.g. as a palm oil plantation.

Direct air capture (DAC): the process of capturing CO2 directly from the atmosphere. Chemicals are used which bind with the CO2 in the air, and the CO2 is then separated to produce a stream of concentrated CO2. This CO2 can then be stored or used in an end product (such as construction) – known as direct air capture and storage (DACS).

Double counting or double claiming or double issuing: when a carbon credit is used more than once, even though this would not further reduce or avoid emissions. When projects are certified their carbon credits will be issued and retired in a carbon registry, preventing double counting from being a risk.


Emissions reduction or emissions avoidance: future emissions from fossil fuels are avoided or reduced through a project e.g. building a solar farm close to a city which is currently powered by a fossil fuel plant will result in less carbon emissions in the future. 

Enhanced weathering: the speeding up of rock weathering or mineralisation as a way of removing and storing carbon. Rocks are ground up into small particles, increasing surface area and removing CO2 from the atmosphere more quickly.

Ex-ante credits: carbon credits representing carbon removal or emissions avoidance that will take place in the future e.g. purchase of credits to finance the planting of a forest, where removal will take place once trees grow and sequester carbon.

Ex-post credits: carbon credits representing carbon removal or emissions avoidance that has already taken place and has been measured.


Forest conservation: protecting a forest from being cut down, typically through incentivising landowners via income from carbon credits

Forest management: implementing practices for the stewardship of forests. In carbon removal, this refers specifically to land management practices which result in increased carbon storage within forests.

Forestry carbon projects: there are a range of different ways that forests are used to avoid emissions and remove carbon from the atmosphere, which can be grouped together as forestry carbon projects. This includes afforestation, forest conservation, forest management, and reforestation. NB: forestry carbon offset projects are different to tree planting projects.


Greenhouse gas emissions: a gas that contributes to the greenhouse effect by absorbing infrared radiation, trapping heat and causing global warming. The primary greenhouse gases are water vapour (H2O), carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and ozone (O3).

Greenwashing: a company or product making itself appear to be environmentally friendly without having done the work to meaningfully reduce its environmental impact. Carbon offsetting can be seen as greenwashing when companies support low-quality projects, are not also reducing their emissions, or approach sustainability as a marketing or PR exercise.


High-quality projects: trusted carbon offset projects that show permanent, additional, and measurable carbon removal or emissions avoidance. They’re often verified (or in the process of being), although this isn’t always the case. They’re also more expensive, as they reflect the true cost of carbon removal/avoidance. Read more in our blog on the difference between high and low quality offset projects.


Leakage: when a reduction in carbon emissions in one area simply shifts activity producing emissions elsewhere, reducing or negating the decrease in emissions e.g. a forest conservation project results in deforestation being avoided, but the company responsible for deforestation moves to a neighbouring forest and cuts down trees there.

Long-lived carbon storage: methods that store carbon for hundreds or thousands of years, which have a low risk of being reversed e.g. mineralisation.

Low-quality projects: carbon offset projects which are not verified and have no proof of permanent, additional, and measurable carbon removal or emissions avoidance. They are typically cheap to purchase but have little or no climate impact – leaving those who buy them at risk of being perceived as greenwashing.


Mineralisation: occurs when CO2 in the air reacts with minerals to become a carbonate, permanently storing the CO2 in solid form. This happens naturally, also known as ‘rock weathering’. The process can be sped up by rocks being ground up into small particles, increasing surface area and removing CO2 from the atmosphere more quickly – also known as ‘enhanced weathering’.


Net zero: when a company reduces their greenhouse gas (GHG) emissions and neutralises the residual amount using carbon removal, resulting in no net impact. NB: this is different from carbon neutral where the emissions offset can be emissions avoidance or carbon removal.


Oxford Offsetting Principles: the Oxford Principles for Net Zero Aligned Carbon Offsetting – known as the Oxford Offsetting Principles for short – provide a framework for approaching business offsetting in the right way and supporting the growth of the carbon market: balancing immediate action with long-term impact whilst keeping costs feasible and taking into account how purchases should change over time to maintain the maximum possible impact.


Permanence: how durable the carbon benefit from carbon removal or emissions avoidance is, taking into account the risk of reversal. For instance, a forest can burn or be cut down in future years so cannot be viewed as permanent.

Project developers: organisations that design and implement carbon offset projects.


Reforestation: turning land that has previously been a forest but that has been converted to some other use back into forest.

Renewables: projects enabling the generation of renewable energy e.g wind turbines, solar farms, reducing reliance on fossil fuels for energy. 


Scope 1 emissions: direct emissions from owned or controlled sources e.g. company vehicles.

Scope 2 emissions: indirect emissions from the generation of purchased energy e.g. purchased electricity.

Scope 3 emissions: all other indirect emissions that occur in the value chain, including both upstream and downstream emissions e.g. emissions associated with the use of products or services sold or used by an organisation.

Science-based target: a corporate sustainability initiative that meets three criteria: 1) it has a clearly-defined emissions reduction pathway, 2) it has a defined baseline amount and year, as well as target goal date, 3) it’s set in line with the latest climate science needed to meet the goals of the Paris Agreement – as defined the by Science Based Targets Initiative (SBTi).

Sequestration: the process of capturing carbon dioxide from the atmosphere, stabilising it in solid or dissolved form, and storing it safely. Usually refers to natural storage e.g. in seaweed or soil.

Short-lived carbon storage: methods of carbon storage which have a higher risk of being reversed e.g. reforestation.

Soil carbon: soil is made in part by broken down organic matter, so it contains the carbon that these plants or animals absorbed during their lifetime. This means that soil is a valuable carbon store or sink.

Sustainability report: a tool for a company or organisation to voluntarily communicate its performance in relation to environmental impact. Typically these reports lack visibility and accountability as a way to approach business sustainability.


tCO2e: greenhouse gases are typically given as tCO2e – tonnes of carbon dioxide equivalent. The equivalent means that the measurement includes greenhouse gases which aren’t carbon dioxide, converted into equivalent amounts of CO2 based on warming potential e.g. methane which has 28-36 times the global warming potential of CO2, so 1 tonne of methane would count as 28-36 tonnes of CO2e.


Voluntary carbon market (VCM): a market enabling the voluntary purchase of carbon credits by a company or individual. This offers a mechanism for financing projects that reduce emissions or remove carbon from the atmosphere, and a way for companies to take climate action by compensating for their emissions or contributing to carbon projects.


We know there can be a lot to wrap your head around when you’re exploring climate impact and carbon offsetting in a business setting; this isn’t an exhaustive list of all the terminology you might come across! 

That’s also why working with a trusted sustainability partner can be incredibly valuable – at Lune we’ve done the hard work already of becoming experts in how businesses should approach carbon offsetting and removal.

And we’re always happy to chat and answer any questions you may have, no matter what stage of your climate journey you’re at - get in touch.

Subscribe to our monthly newsletter – and get a free copy of our Complete Guide to Offsetting