Glossary
This is a new industry for many people and the jargon can get complicated. I hope this glossary of carbon free aviation technical terms helps you better understand the industry and the technology that is driving it.
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Z
A
A4E
European Airline Association
Anthropogenic
This describes something which was caused by human activity. In the context of this website, it refers to climate change caused by GHG emissions due to industrial activity and land use change.
ASK
Available Seat Kilometer
ATAG
Air Transport Action Group
AtJ
Alcohol to Jet: a process where alcohol is converted into jet fuel, this is one process for manufacturing SAF
ASTM
American Society of Testing and Materials: regulatory body in the US responsible for certifying the specific type of SAF and the maximum % blend that can be mixed with traditional jet fuel
B
Block Time
Duration of an aircraft flight from the time the aircraft starts moving until the parking park is applied at the destination airport, it includes taxi out, flight and taxi-in time, the phrase refers to the blocks or chocks used to start a parked aircraft from moving and are removed from around the wheels prior to push back and placed once again once the aircraft is parked.
Book and Claim
The Book and Claim System is the cost effective roll out of SAF. To minimize costs, SAF can be produced and dropped into aviation fuel mix at the locations that it is most economical to produce, depending on availability of feedstocks, for example. However, any airline can pay the cost difference for SAF v’s fossil jet fuel and “claim” the carbon offset benefit, even though the fuel was not used in one of its own aircraft.
C
Carbon Budget
This term refers to a concept that there is a maximum amount of additional carbon dioxide that can be released into the atmosphere before a threshold of temperature increase will be crossed. Globally the remaining carbon budget to limit temperature increase to 1.5C with 50% probability is 440GtCO2. If only 230GtCO2 additional carbon dioxide is released the probability of the temperature increase being limited to 1.5C increases to 66%, at 670GtCO2, that probability drops to 33%. The global carbon budgets can be subdivided into national and regional carbon budgets.
CBAM
Carbon Border Adjustment Mechanism: This is a tax applied on goods imported from outside a region with carbon pricing to put importers on a level playing field with producers inside the region who do have to abide by the carbon pricing rules.
CCS
Carbon Capture and Storage. It is process of chemically capturing CO2 (separating it from air) and storing it underground where it will never be released back into the atmosphere. The CO2 is captured at a source of large emissions, for example natural gas wells, coal-fired power plants or cement production plants. The captured CO2 is typically injected it into the same porous underground rock formations from which hydrocarbons are extracted. CCS is often done in conjunction with hydrocarbon extraction as a form of enhanced oil recovery, the carbon that is injected into the rock, pushes out more of the oil or gas that is being mined.
This technology has held huge promise and attracted significant investment for many years. Because of the volume of carbon that it can remove from the atmosphere, and its potential to “clean” industries like coal mining or cement production. However the process has only proven to be economical in limited instances, typically when the captured carbon is used for enhanced oil recovery.
CCUS
Carbon Capture, Utilization and Storage is similar to CCS but with CCUS describes a technology that uses the carbon to
Carbon Leakage
This is a phase used to describe the movement of manufacture from a region where carbon is priced (either directly with a carbon tax or indirectly via an ETS) to a region where producers can emit carbon without any cost. Carbon leakage defeats the purpose of carbon pricing for any footloose industry such as steel production, since the carbon just get emitted in another country. It can be remedied with a carbon border adjustment mechanism (tax) to equalize the cost.
CDM
Clean Development Mechanism
CDR
Carbon Dioxide Removal: activities which take carbon dioxide out of the atmosphere. There are usually two methods considered as CDR: afforestation and CCS.
CER
Certified Emissions Reduction: carbon emission credits purchased in order to offset emission in excess of a company’s permitted carbon limit. This forms type of carbon credit from the balancing mechanism of the EU, Canada and California’s GHG cap and trade system.
CI
Carbon Intensity
COP
Conference of Parties: These are meetings of all signatories (parties) of the United Nations Framework Convention on Climate Change (UNFCC). The first COP was held in Berlin in 1995. This is known as COP01, each subsequent annual. conference in named in numerical sequence. COP03 in Kyoto in 1997 produced the Kyoto Protocol, COP21 in Paris, the Paris Agreement.
CST
Clean Skies for Tomorrow: This is a coalition of over 80 organizations, including airlines, aircraft and engine manufacturers, fuel supplier and airport operators and are working together to scale the production of SAF and decarbonize aviation.
CORSIA
Carbon Offsetting and Reduction Scheme for International Aviation
D
DAC
Direct Air Capture: method of capturing carbon dioxide directly from air in order to be used in the production of synthetic hydrocarbon fuels. This process equates to a carbon neutral energy sources since the CO2 produced from burning the fuel is just returned to the air, where it was started out.
E
EAA
Experimental Aircraft Association: This is an association of pilots and aircraft enthusiasts with an interest in flying, building, and restoring recreational aircraft.
EASA
European Union Aviation Safety Agency
ECF
European Climate Foundation is a philanthropically funded NGO, focused on developing research and building consensus among the stakeholder in civil society to achieve a smooth transition to net zero carbon emissions by 2050. It is a major funder of climate action in Europe.
EFP
Efficient Flight Profile: method of aircraft approach to landing which allows continuous descent and minimizes fuel burn, emissions, and noise.
EGD
European Green Deal is a collection of policy and legislative initiatives by the European Commission with the goal of making Europe the first carbon neutral continent by 2050. The European Green Deal is a member of the European Commission, reporting to the Euorpean Commission President. It has the remit of reviewing existing laws and proposing new legislation to enable the European Union to achieve it’s emissions targets.
EIS
Entry Into Service is the moment that an new aircraft is certified and allowed to start operating commercial flights with an airline.
Emissions
In the context of aviation, GHG emissions from airlines are considered in 3 categories:
- Scope 1: Emissions caused by direct operations; burning fuel, both aircraft fuel and ground handling equipment fuel. For airlines Scope 1 emissions are typically 79%.
- Scope 2: Emissions caused by purchasing electricity used by the airline. For an airline Scope 2 emissions are typically <1%.
- Scope 3: Emissions caused through the process of extracting and transporting jet fuel from well to tank (WTT) and also the emissions created during the transmission and distribution of electricity that is used by the airline. For an airline Scope 3 emissions are typically 20%.
Emissions Gap Report
The Emissions Gap Report is an annual review of the difference between what global GHG emissions are projected to be in 2030 verses where they need to be to avoid the worst impactos of climate change. The report is published by the UNEP. You can find the 2020 report here.
ESG
Environment Social Governance
ESG Rating Agency
ESG Rating Agency
F
FAA
Federal Aviation Authority
FEED
Front End Engineering Design is a step in the construction of large industrial projects. It defines the technical requirements and identifies the main costs of the project, such as the construction of SAF gasification and refining plants. FEED comes after the feasibility study and conceptual design of the project and before bids are submitted for the construction of the project.
FOG
In the context of carbon free aviation, FOG refers to waste fat, oils and gases as a group of feedstocks used to manufacture SAF using the HEFA conversion pathway.
FPF
Feedstock Processing Facility, in the context of SAF, this is plant that processes the biomass feedstock into a syncrude, which is then refined into aviation fuel.
FT-SPK
FT-SPK Fischer-Tropsch Synthetic Paraffinic Kerosene: SAF made from syngas, with two possible production methods; gasification of feedstock such as waste or residues; and electrolysis of CO2. Approved for use in aircraft by ASTM since 2009 with a maximum blending rate of 50% with traditional jet fuel.
G
Gasification-FT
Gasification/Fischer-Tropsch
GHG
Green House Gas: any gas that contributes to the warming of the earth by trapping the sun’s heat in its atmosphere. CO2 constitutes 80% of GHGs. Because aircraft emit GHG’s high in the atmosphere the global warming effect is approximately twice that of similar emission at ground level. In order to harmonize the impact of various GHGs, they are all measured in Tons of CO2 equivalent.
Green Hydrogen
Hydrogen fuel made by removing the oxygen molecules from water (H2O) using electrolysis and powered by electricity from a renewable source. This process is currently very expensive.
GST
Global Stock Take: This is a process defined in the Paris Agreement where from 2023 each Party to the agreement must report their GHG emissions. This process repeats every 5 years until 2050. Please note that international aviation is not included in the Paris Agreement.
H
HEFA
Hydroprocessed Esters and Fatty Acids: type of biofuel made by hydroprocessing oils and fats. HEFA can be used in all diesel engines and as aviation bio jet fuel.
HEFA SPK
Hydroprocessed Esters and Fatty Acids Synthetic Paraffinic Kerosene, SAF certified by ASTM in 2011 for use with traditional jet fuel in a blend up to 50%; commonly referred to simply as HEFA.
HERA
Hybrid Electric Regional Aircraft
HVO
Hydrotreated Vegetable Oil
I
IATA
International Air Transportation Association is the industry representative for most major scheduled airlines. It is focused on the commercial aspects of aviation such as ticketing, managing the clearing house for interline ticketing agreements, and interline baggage transfer between airlines.
ICCT
International Council on Clean Transportation in is an independent nonprofit organization founded to provide first-rate, unbiased research and technical and scientific analysis to environmental regulators.
ICOA
International Civil Aviation Organization is a branch of the United Nations and is the international representative of each member country’s national civil aviation authority (i.e. the FAA in the US, EASA in Europe etc). ICAO is focused on technical and political issues and they relate to all civil aviation, not just scheduled airlines.
IEA
International Energy Agency is an intergovernmental organized made up of OECD member countries. It acts both as an information source on energy statistics and as a policy advisor to its member states to ensure secure affordable and sustainable energy for all.
ILUC
Induced or Indirect Land Use Change, see main article on LUC.
IRENA
IRENA International Renewable Energy Agency is an intergovernmental organization comprised of over 160 countries. It was created to facilitate cooperation, advance knowledge, and promote the global transition from fossil fuels to renewable energy. Ironically, it is headquartered in Saudi Arabia.
J
JZC
Jet Zero Council: This is a partnership between industry and the UK government formed to develop the UK’s ability to deliver both net zero and zero emission commercial aircraft technologies. The partnership was formed in 2020 and is made up of two UK government ministers and the CEOs of various airlines, airports and fuel suppliers.
K
Kerosene
Traditional fossil Jet A1 and Jet A fuels are types of kerosene. Kerosene is often used to refer to jet fuel.
L
LCA
Life Cycle Assessment, this expression is often using in reference to the GHG that a fuel produces. For example, the LCA GHG reduction of waste to fuel SAF compared to traditional jet fuel could be 80%. This is because the carbon from the waste would have been released back into the atmosphere whether it was put in landfill, incinerated, or transformed into SAF and burnt in jet engine. Whereas the fossil jet fuel is introducing 100% new carbon into the atmosphere. Carbon which had been previously stored underground.
LUC
Land Use Change refers carbon emissions caused when land use is changed from being a carbon sink, to another activity. For example, when rain forest is cut down to grow sugar cane. This is highly relevant in SAF biofuel feedstocks. Induced Land Use Change (ILUC) is used as a measure of the net carbon impact of land use change.
LULUCF
Land Use, Land Use Change and Forestry, is an expanded acronym for Land Use Change.
M
MBM
Market Based Measures: These are policy tools designed to achieve environmental goals by creating incentives and costs to encourage emitters to reduce their production of greenhouse gases, rather than using the direct policy tools of limits and regulations.
MSW
Municipal Solid Waste: This is a viable feedstock for the production of syngas, which can then be processed into biofuel.
MtCO2e
Metric tons of carbon dioxide equivalent: This is the unit used to measure the global warming impact of emissions. It is calculated by multiplying the mass of GHG (Green House Gases) emitted in the relevant activity, by the GWP (Global Warming Potential) of each gas.
N
NDC
Nationally Determined Contributions: Under the Paris Agreement each country who is party to agreement must submit a plan for the climate action they will take to reduce their GHG emissions. This plan is called their Nationally Determined Contribution. Aviation emissions are not included in the Paris Agreement.
O
P
pax-km/L
Passenger Kilometers per liter of fuel burnt – unit used to measure the fuel efficiency of airlines at a fleet level. This unit calculates how much fuel was used to transport one passenger one kilometer. Please note that load factor and seating configuration will have a bigger influence than airline age or engine efficiency, getting more people on to the plane move the needle more than incremental gains in engine efficiency
PtL
Power to Liquid: using renewable electricity to make liquid hydrogen
Q
R
RCF
Recycled Carbon Fuel
RED II
Renewable Energy Directive II is a recast version of a European Union Directive that sets minimum targets for GHG reductions. RED II includes the transportation sector, which was excluded from the original Directive. It also stipulates targets regarding the use of food-based biofuels and ILUC caused by the need for biofuel feedstocks.
The national targets set out in this Directive are legally binding upon the EU Member States.
Aviation is not obliged to partake in RED II.
REDD+
Reduced Emissions from Deforestation and Degradation: This is a MBM where forestry projects generate carbon credits based on the carbon that would have been emitted had the deforestation occurred in the area of the project. These carbon credits can then be sold to companies who wish to offset their emissions. The number of carbon credits generated by REDD+ project is calculated by assuming that deforestation would have occurred in the reference area at the same rate as some comparable baseline area. Since this is ultimately trying to prove a negative, the validity of these have been questioned by some conservation group. Nevertheless, they are an important source of funding to prevent deforestation in areas with weak or no environmental protection from the local government.
REC
Renewable Energy Certificate
RFNBO
Renewable Fuels of Non-Biological Origin
RPK
Revenue Passenger Kilometer: measure of aviation traffic, flying one paying passenger a distance of one kilometer.
RTK
Revenue Ton Kilometer: measure of aviation traffic, flying one ton of payload a distance of one kilometer, for the purposes of analyzing the aviation industry as a whole, RTK is a more accurate measure of traffic since if can include passenger, baggage and cargo.
RTFO
Renewable Transportation Fuel Obligation
RWGS
Reverse Water Gas Shift: method of manufacturing PtL fuels
S
SAF
Sustainable Aviation Fuel: Sustainable Aviation Fuel is a replacement for standard jet fuel, but it is made with a sustainable feedstock. It is estimated that replacing jet fuel with SAF reduces carbon emission by about 80% over the lifecycle of the fuel. SAF is “drop-in” fuel, it can be blended with traditional jet fuel without any modification to the engine or fueling infrastructure.
SDG
Sustainable Development Goals are 17 goals adopted by all member states of the UN, via the UN General Assembly in 2015, they cover the most urgent environmental, political and economic challenges facing the world. 2030 is the targeted date to achieve these goals.
SDG Goal 13
SDG Goal 13 is Climate Action. It aims to limit global warming to 1.5C by reducing global carbon emissions by 45% from 2010 to 2030 and reach net zero emissions by 2050. Many major airlines have committed to the net neutral target by 2050 but there are few specific commitments to the interim 2030 target.
SLB
Sustainability Linked Bonds: Bonds that have their coupon price linked to KPI targets related to ESG goals. The KPI targets for airlines would be heavily weighted towards CO2 emissions. And the targets must be ambitious, measurable and go beyond any business as usual scenario.
SLBs are a new financial product, and are an attempt to link investor demand for businesses making a genuine and measurable contribution in the area of ESG, with companies that want to realize a tangible gain from their efforts in the area of ESG.
Given the high profile of aviation, SLBs offer airlines a practical mechanism to display their ESG credentials and have these verified by a third party.
SLL
Sustainability Linked Loan: Generally term loans, but could also be a revolving line or credit or a letter of credit. The loan has KPI targets linked to the loan, for example 20% reduction in CO2 emissions within 5 years. These KPIs must be ambitious, measurable and must go beyond environmental improvements what would have happened anyway under a business as usual scenario. Typically these KPIs include not only GHG reductions, but also reduction in water and land use.
The interest rate the of the loan is linked to the borrowers business performance verse their target KPIs.
SOEC
Solid Oxide Electrolyser Cell: method of manufacturing PtL fuels
SPAC
Special Purpose Acquisition Company – is a shell company with no operations of its own that raises capital by floating on an exchange via an initial public offering with the explicit purpose of purchasing an operating business. There may or may not be an intended target company for purchase at the time of floatation, if there is, this is not disclosed. Using this financial vehicle, companies can access public funds while avoiding the scrutiny that would come with an operating business going through an IPO process. The popularity of SPACs has exploded in recent years, and they are frequently used to fund company in the electrical aviation space
SPK/A
Synthetic Paraffinic Kerosene/Aromatics: SAF similar to FT-SPK, approved by ASTM since 2015 to be blend with traditional jet fuel up to 50%.
SRF
Solid Recovered Fuel: This is the faction of MSW that is left after recyclable materials and organic materials have been removed and it can be used as a feedstock for the production of syngas and further processed into biofuel.
Structural Batteries
A technology under development where carbon fiber serves simultaneously as a battery and a load bearing structural element of device it is powering. In aviation, this would mean that the carbon fiber fuselage and wings also serve as the battery which powers the aircraft. Physics World called this technology one of the top 10 breakthroughs of 2018.
T
Taxi Time
The time an aircraft spends taxiing from its parting position to the moment it leaves the ground, and the moment it lands until the moment the aircraft parks.
TCRE
Transient Climate Response to Cumulative Emissions is the ratio of the change in global average temperature to the change of carbon dioxide in the atmosphere. It is a ratio used in climate modelling that assumes a linear relationship between these two values. TCRE is useful for calculating the carbon budget of the plant – how much more carbon can be emitted before a temperature increase threshold of, for example 1.5C, is reach. However, the relationship between carbon emissions and temperature increase is not linear due to the positive feedback effects of melting permafrost, leading to less sunlight being reflected, amount many other factors. The estimate for TCRE developed by the IPCC in their Special Report on 1.5C (SR15) is 0.44C per 1,000GtCO2.
TRL
Technology Readiness Level
U
UCO
Used Cooking Oil is the most common feedstock for SAF made via the HEFA pathway. This feedstock and production method is the most commercially and technologically mature way to make SAF.
UNEP
United Nations Environment Program is an organization charged with coordinating the implementation of environmental dimensions of sustainable development within the UN system.
UNFCCC
United Nations Framework Convention on Climate Change: This is first UN convention dealing specifically with climate change. It was agreed to during the Earth Summit in Rio in 1992 (officially known as the United Nations Conference on Environment and Development). Since 1995 the active signatories to UNFCC (currently 197 countries) have been meeting annually at an event known as COP in order to advance the progress in dealing with climate change.
V
VER
Voluntary Emissions Reduction: This term refers to a type of carbon offset that is bought on a voluntary basis because the carbon emitter or the customer of the carbon emitter has chosen to voluntarily offset part or all of the GHG’s produced by the activity they will engage in. May airlines provide customers an option of voluntarily purchasing carbon offsets at the time they purchase their flight ticket, in order to offset the carbon they will produce by taking the flight
VTOL
Vertical Take Off and Landing: This is the ability of an aircraft to take off and land without the need of a runway.