Glossary

Welcome to our glossary. A categorized reference list to learn about some of the terminology used in sustainability. Terms are categorized by relevant topic below and you can always contact us for more information about a topic or term.

Carbon Offsetting

Carbon Offset/Credit: used interchangeably, a tradeable, verified credit for mitigating 1 metric ton (mt) of CO2 by paying someone else to avoid 1mt of CO2-equivalents elsewhere.

Carbon Dioxide (CO2) and Carbon Dioxide Equivalent(CO2e): CO2 is one of the most abundant greenhouse gases (GHG) in the atmosphere. CO2 is a by-product of industrial processes, burning fossil fuels, and land use changes. CO2e is a unit of measurement used to compare the relative climate impact of different greenhouse gases.

Offset Project: Infrastructure created to produce a carbon offset.

Carbon Offset Standard: An established set of rules that exist to ensure offsets meet stringent requirements to ensure transparency and credibility. Most used in the voluntary market include American Carbon Registry (ACR), Climate Action Reserve (CAR), Gold Standard (GS), Verified Carbon Standard (VCS).

Registry: Public registry and entity that guarantees carbon offset credits are not double counted, and tracks carbon offset production, ownership, and retirement. Registries are usually stakeholders in methodology development and are often synonymous with Standards.

Protocol/Methodology: Methodologies established by Standards and used to verify an offset project and create an offset. They cover accounting and monitoring, reporting, verification and certification rules. An outline of procedures to determine project eligibility, additionality, baseline and project emissions for a project type.

Double Counting: When two entities attempt to claim the same carbon emission reduction.

Project Developers: Entity that produces the Offset Project.

Vintage: Carbon credits are like wine, they have a specific vintage - the year the offset was mitigated and verified.

Comprehensive Carbon Offsetting: Factoring in non-carbon emissions and impacts into a carbon offsetting program using Radiative Forcing Indices to convert their impact into CO2e amounts.

Radiative Forcing Index: A measure of the impact of a GHG or other emission on the natural warming equilibrium of the earth relative to CO2. Allows for conversion of the climate impact of non-CO2 impacts to CO2e amounts.

Sustainable Aviation Fuel

Fossil Jet Fuel: Jet fuel certified under ASTM D1655 typically denoted as JetA that is produced from the refinement of oil (a fossil fuel).

Sustainable Aviation Fuel (SAF): Jet fuel that comes from non-fossil sources that are also classified as sustainable feedstocks. Allowing the production of jet fuel certified under ASTM D7566 (Certification pathway for synthesized fuels). By blending the SAF with fossil jet fuel up to 50-50, it can be certified under the same certification as fossil (D1655) and becomes a drop-in sustainable solution.

Feedstock: The underlying source of the fuel to be refined into jet fuel. For typical jet fuel, the feedstock would be petroleum. For SAF, feedstocks are typically wasted cooking oil or municipal waster. In order to be sustainable, feedstocks must not compete with arable land (ie. cannot be grown on land that could be used for growing food or forests) or edible feedstocks (ie. corn).

Blend: The mix of SAF to JetA . No more than 50% SAF is mixed with JetA today. 30/70 means 30% SAF and 70% JetA in the fuel.

Drop-In Fuels: A completely interchangeable and compatible with conventional jet fuel when blended with conventional jet fuel. No modifications are needed to storage, fueling equipment, nor engines to use a drop-in fuel.

Book-and-Claim: Jet operators can purchase SAF for use at an airport where it is physically unavailable and still receive a credit for its reductions while it is put into the fuel supply elsewhere. Book and claim works very similar to carbon offsetting where a reduction is recorded and verified in one place, traded, and claimed by another user.

SAFc: A Sustainable Aviation Fuel Credit (SAFc) is measured as one “neat” (undiluted) gallon of SAF. It is like a carbon offset and used under the book and claim system.

Other

Nitrogen Oxides: Typically depicted as NOx, Nitrogen Oxides are a family of poisonous, highly reactive gases. These gases form when fuel is burned at high temperatures. NOx pollution is emitted by automobiles, trucks, and various non-road vehicles (e.g., construction equipment, boats, etc.), as well as industrial sources such as power plants, industrial boilers, cement kilns, and turbines. NOx often appears as a brownish gas. (EPA)

Contrail-Induced Cirrus Cloudiness: Contrails are linear clouds trailing an aircraft that are created from ice forming around particulate emissions from the engines of an aircraft in the right temperature and humidity environment. They can persist for hours to days and can combine with other contrails or grow themselves into larger cirrus (high altitude, wispy) clouds. Their impact is not perfectly understood, but research suggests their net warming impact is nearly double that impact of CO2 emissions.

Whole Aircraft Sustainability: Looking at non-emissions impacts from flying, including everything from on-board waste products to construction materials used in manufacturing the airframe and aircraft interior.