Annex I countries: The group of 37 developed countries with commitments to reduce GHGs under the Kyoto Protocol.

Biofuel: Fuel produced from biomass.

Carbon intensity: A metric of a product’s impact on the environment, measured in terms of total emissions produced in units such as gCO2eq/MJ.

Carbon offsets: Accounting representations (usually certificates) of CO2eq volumes removed from the Earth’s atmosphere by a number of methods, often tradable on ETSs.

Carbon offsetting: A mechanism allowing entities to pay for CO2 emissions reduction projects carried out by other entities and claim the CO2 emissions reductions themselves. 

eFuels: The blanket term for a range of synthetically produced fuels using hydrogen produced via electrolysis and renewable power.

JET A-1: The principal fuel used in passenger and freight aircraft today, described by ASTM standard 1655 and with a flashpoint of 38°C and freezing point of -47°C. The variant Jet A, used principally in the USA, has a higher freezing point of -40°C. Another variant, Jet B, has an even lower freezing point (-60°C) but higher volatility. JP-5 and JP-8 are military variants designed for use in a variety of vehicles. All are kerosene-type fuels.

Kyoto Protocol: An international treaty extending the 1992 United Nations Framework Convention on Climate Change, which committed States to reducing GHGs based on the scientific consensus that global warming is occurring. Superseded by the Paris Agreement in 2015.

Paris Agreement: Successor to the Kyoto Protocol, the Paris Agreement is an international treaty on climate change, adopted in 2015 and in effect today, containing binding commitments to reduce GHGs and combat climate change. Also known as the Paris Accords.

Synthetic fuels or synfuels: Hydrocarbon fuels produced through chemical processes combining carbon monoxide and hydrogen (also known as syngas).