Glossary of Terms

BIOFUELS Fuel made from plant material, such as wood, straw, and ethanol from plant matter.


BIOGENIC CO₂e EMISSIONS CO₂e emissions from the combustion or biodegradation of biomass. Biogenic gas (biogas) Methane that is produced from a biomass resource, such as animal waste, agricultural waste, landfill gas, municipal waste, or digester gas.


BIOMASS Any material or fuel produced by biological processes of living organisms, including organic non-fossil material of biological origin (e.g., plant material), biofuels (e.g., liquid fuels produced from biomass feedstocks), biogenic gas (e.g., landfill gas), and biogenic waste (e.g., municipal solid waste from biogenic sources).


CARBON, C An element with relative atomic mass of 12. Its principal forms are graphite, diamond, and buckminsterfullerene. Carbon is the main component of particulate matter (PM) and particulate number (PN) emissions from internal combustion engines running on hydrocarbon fuels. This is also referred to as ‘soot’. Confusingly reference is made to ‘carbon’ when the meaning is carbon dioxide (CO₂) or carbon dioxide equivalent (CO₂e) e.g. carbon intensity, carbon neutral, zero carbon – vide infra.


CARBON MONOXIDE, CO It is one of the two oxides of carbon. It is toxic. It is common in domestic gaseous fuel as it reacts with oxygen in air to form carbon dioxide.


CARBON DIOXIDE, CO₂ A naturally occurring gas, is also a product of burning hydrocarbon fossil fuels (such as oil, gas, and coal), of burning biomass, of land-use changes (LUC) and of industrial processes (e.g., cement production). It is the principal anthropogenic greenhouse gas (GHG) that affects the Earth’s radiative balance. It is the reference gas against which other GHGs are measured and therefore has a global warming potential (GWP) of 1. (Current list, AR5 issued by the Intergovernmental Panel on Climate Change, IPCC). 

Carbon dioxide is essential for photosynthesis, a process responsible for all vegetative growth processes. Photosynthesis requires water, light and CO₂ and occurs in the green leaves (specifically at the chlorophyll molecule). The by-product of photosynthesis are oxygen and water.


CO₂ EQUIVALENT (CO₂e) The universal unit of measurement to indicate the global warming potential (GWP) of each greenhouse gas, expressed in terms of the GWP of one unit of carbon dioxide. It is used to evaluate releasing (or avoiding releasing) different greenhouse gases against a common basis.


CO₂ EQUIVALENT (CO₂-eq) EMISSION The amount of carbon dioxide (CO₂) emission that would cause the same integrated radiative forcing or temperature change, over a given time horizon, as an emitted amount of a greenhouse gas (GHG) or a mixture of GHGs. 


CARBON OFFSETTING Carbon emissions generated through an activity (like flying) can be calculated, and then the equivalent amount “paid off” via a scheme which removes carbon from the atmosphere (such as tree planting). To work, the "carbon removal" scheme or project must be in addition to existing schemes.

NET ZERO CARBON EMISSIONS removing as many emissions as we produce. Net zero does not mean they are going to reduce greenhouse gas emissions to actual zero, it means they are going to reduce their emissions a lot (or just a bit) and fund an offsetting project to deal with their remaining emissions.  It is a bit like paying someone to stay sober so you can drink for both of you.

Net zero GHG emissions can be confused with net-zero carbon emissions, but when accurately used, means all greenhouse gas emissions decline to zero, as opposed to just carbon dioxide. This is the same concept as net zero carbon emissions but conveys a net zero emissions target for CO₂ and all non-CO₂ gases. 

CARBON NEUTRALITY means annual zero net anthropogenic (human caused or influenced) CO₂ emissions by a certain date.

By definition, carbon neutrality means every ton of anthropogenic CO₂ emitted is compensated with an equivalent amount of CO₂ removed (e.g. via carbon sequestration), but this term has been used differently on occasion.

DOUBLE COUNTING Two or more reporting companies claiming the same emissions or reductions in the same scope, or a single company reporting the same emissions in multiple scopes.


DECARBONIZATION is framed around decreasing the ratio of carbon dioxide (CO₂) or all greenhouse gas emissions related to primary energy production. While full decarbonization means zero unabated (not captured by carbon sequestration or storage) CO₂ emissions from energy generation and industrial processes, decarbonization doesn’t imply zero emissions, as emissions can be balanced by carbon sequestration if adequate reductions or enhanced carbon sinks exist. To effectively communicate the scale of change needed, the term must be accompanied by a timeframe and rates of decarbonization.

CARBON SEQUESTRATION the long-term storage of carbon in plantssoils, geologic formations, and the ocean. Carbon sequestration occurs both naturally and as a result of anthropogenic activities and typically refers to the storage of carbon that has the immediate potential to become carbon dioxide gas. In response to growing concerns about climate change resulting from increased carbon dioxide concentrations in the atmosphere, considerable interest has been drawn to the possibility of increasing the rate of carbon sequestration through changes in land use and forestry and also through geoengineering techniques such as carbon capture and storage.


CARBON CYCLE Carbon is transported in various forms through the atmosphere, the hydrosphere, and geologic formations. One of the primary pathways for the exchange of carbon dioxide (CO₂) takes place between the atmosphere and the oceans; there a fraction of the CO₂ combines with water, forming carbonic acid (H2CO3) that subsequently loses hydrogen ions (H+) to form bicarbonate (HCO3−) and carbonate (CO32−) ions. Mollusc shells or mineral precipitates that form by the reaction of calcium or other metal ions with carbonate may become buried in geologic strata and eventually release CO₂ through volcanic outgassing. Carbon dioxide also exchanges through photosynthesis in plants and through respiration in animals. Dead and decaying organic matter may ferment and release CO₂ or methane (CH4) or may be incorporated into sedimentary rock, where it is converted to fossil fuels. Burning of hydrocarbon fuels returns CO₂ and water (H₂O) to the atmosphere. The biological and anthropogenic pathways are much faster than the geochemical pathways and, consequently, have a greater impact on the composition and temperature of the atmosphere.

CARBON CAPTURE AND STORAGE Some policy makers, engineers, and scientists seeking to mitigate global warming have proposed new technologies of carbon sequestration. These technologies include a geoengineering proposal called carbon capture and storage (CCS). In CCS processes, carbon dioxide is first separated from other gases contained in industrial emissions. It is then compressed and transported to a location that is isolated from the atmosphere for long-term storage. Suitable storage locations might include geologic formations such as deep saline formations (sedimentary rocks whose pore spaces are saturated with water containing high concentrations of dissolved salts), depleted oil and gas reservoirs, or the deep ocean. Although CCS typically refers to the capture of carbon dioxide directly at the source of emission before it can be released into the atmosphere, it may also include techniques such as the use of scrubbing towers and “artificial trees” to remove carbon dioxide from the surrounding air.

GLOBAL WARMING POTENTIAL A factor describing the radiative forcing impact (degree of harm to the atmosphere) of (GWP) one unit of a given GHG relative to one unit of CO₂.


The HIGH CARBON STOCK (HCS) approach is a methodology that distinguishes forest areas for protection from degraded lands with low carbon and biodiversity values that may be developed. The methodology was developed with the aim to ensure a practical, transparent, robust, and scientifically credible approach that is widely accepted to implement commitments to halt deforestation in the tropics, while ensuring the rights and livelihoods of local peoples are respected.


SUSTAINABLE The concept of sustainable development was described by the World Commission on Environment and Development in its 1987 book Our Common Future.[1] Its definition of "sustainability", now used widely, was, "Sustainable development should meet the needs of the present without compromising the ability of future generations to meet their own needs."[1]

When referring to methods of producing energy, the term "sustainable energy" is often used interchangeably with the term "renewable energy". In general, renewable energy sources such as solarwind, and hydroelectric energy are widely considered to be sustainable. However, particular renewable energy projects, such as the clearing of forests for the production of biofuels, can lead to similar or even worse environmental damage when compared to using fossil fuel energy. There is considerable controversy over whether nuclear energy can be considered sustainable, for example among European Union[4] and Japanese[5] decision makers.