Cut Emissions Transportation Fuel Switching

Deploy Sustainable Aviation Fuel

Worth Watching
Image
Airline jet engine

Sustainable aviation fuel (SAF) is a low-carbon alternative to conventional jet fuel. It is made from renewable feedstocks, including waste oils, agricultural residues, and renewable electricity. SAF can substantially reduce life-cycle GHG emissions and is already in use in commercial flights at low blending levels. Advantages include its compatibility with existing aircraft and fueling infrastructure, its potential to reduce emissions for long-haul aviation, and its ability to reduce emissions from organic waste streams. Disadvantages include limited feedstock availability, high costs, variable climate benefits depending on production methods, and challenges in scaling up supply to meet global demand. We conclude that Deploy Sustainable Aviation Fuel is “Worth Watching” as part of a broader portfolio of aviation decarbonization strategies.

Last updated June 30, 2025

What is our assessment?

Based on our analysis, sustainable aviation fuel (SAF) is a promising climate mitigation solution for reducing emissions in the aviation sector, particularly for long-haul flights where few alternatives exist. However, it is not yet cost-effective and faces significant challenges to scaling production due to severe feedstock restraints, high risks to land, and the need to meet robust sustainability standards. Based on our assessment, SAF is a climate solution that is “Worth Watching."

Plausible Could it work? Yes
Ready Is it ready? Yes
Evidence Are there data to evaluate it? Yes
Effective Does it consistently work? Yes
Impact Is it big enough to matter? Yes
Risk Is it risky or harmful? No
Cost Is it cheap? No

What is it?

Sustainable aviation fuel (SAF) is a low-carbon alternative to conventional jet fuel that reduces life-cycle greenhouse gas emissions from fuel production by using only non-petroleum feedstocks such as waste oils, agricultural residues, and municipal solid waste. It is usually produced using renewable electricity and captured CO₂. SAF is produced through chemical processes that convert these feedstocks into fuels that meet the same technical standards as fossil-based jet fuel, allowing them to be blended and used in existing aircraft engines and fueling infrastructure without modification. All SAFs approved by ASTM International, the body that sets fuel standards for aviation, are certified only for use in blends. No SAF is yet certified for 100% use in commercial aircraft (also known as “neat SAF”) for passenger flights.

Does it work?

The basic idea of sustainable aviation fuel is technologically sound and supported by decades of research into low-carbon fuel alternatives for aviation. Multiple SAF production pathways – such as hydroprocessed esters and fatty acids (HEFA), Fischer-Tropsch synthesis (FT), and alcohol-to-jet (ATJ) – have been approved by international aviation standards bodies, and several have been demonstrated at commercial scale. Real-world use of SAF is already underway: over 450,000 commercial flights have flown using SAF blends as of early 2025. SAF is currently being supplied at major airports in Europe, the United States, and Asia, with dozens of airlines integrating SAF into operations or entering offtake agreements. While current production remains limited (less than 0.5% of global jet fuel supply), government mandates, tax credits, and airline demand are driving the need for rapid scale-up. SAF is considered one of the most evidence-backed and immediately deployable climate solutions for reducing aviation emissions.

Why are we excited?

Sustainable aviation fuel offers several compelling advantages that make it a potential pathway for reducing aviation emissions. By reducing emissions 60-70% per ton compared to jet fuel, SAF could potentially avoid 0.1–0.2 Gt CO₂/yr by 2050. It can also reduce contrails. SAF can be used in existing aircraft and fueling systems without requiring new infrastructure or major redesigns. This makes it one of the few ready-to-deploy solutions for long-haul and international flights, which are difficult to electrify or replace. SAF production from waste oils and residues can also deliver additional benefits, such as reduced methane emissions from organic waste streams and improved waste management. SAF offers a potentially scalable, technically feasible route to emissions reductions in a sector with few alternatives. Growing policy support, rising carbon prices, and airline demand are accelerating development. 

Why are we concerned?

Despite its promise, sustainable aviation fuel faces significant limitations, risks, and challenges that could constrain its impact and scalability. First, supply is a critical constraint. Due to limited feedstock availability, SAF is highly unlikely to be able to meet the ambitious 2050 goals set by ICAO, ReFuelEU Aviation, and other industry organizations, associations, and governmental institutions. This means that SAF must be combined with other strategies, like demand reduction and new aircraft technologies, to achieve full decarbonization. There are also major ecological and social risks, including competition for land and feedstocks that could displace food production or degrade ecosystems, as well as unequal access to the benefits of SAF deployment. Scaling synthetic SAF (e-fuels) requires vast amounts of clean electricity, water, and CO, raising concerns about resource use and trade-offs with other sectors. Another major concern is cost. Current SAF prices are substantially higher than fossil jet fuel, ranging from US$300 to over US$1,500 per t CO avoided, depending on the pathway. Without strong policy support, this cost premium poses a barrier to widespread adoption. Additionally, life-cycle emissions reductions vary widely depending on the feedstock and production pathway. While some SAFs (e.g., e-fuels using renewable electricity) can achieve near-zero emissions, others, especially those using food crops or poorly regulated waste streams, may deliver modest or uncertain climate benefits. Measurement, reporting, and verification of actual emissions reductions can be complex, especially when land-use change, indirect emissions, or supply chain impacts are involved. SAF combustion still contributes to climate impacts from contrails (albeit reduced compared to jet fuel), nitrogen oxides, and soot.

References

Alternative Fuels Data Center. (n.d.). Sustainable Aviation Fuel. https://afdc.energy.gov/fuels/sustainable-aviation-fuel

Bardon, P., & Massol, O. (2025). Decarbonizing aviation with sustainable aviation fuels: Myths and realities of the roadmaps to net zero by 2050. Renewable and Sustainable Energy Reviews, 211, 115279. https://doi.org/10.1016/j.rser.2024.115279

Boyles, H. (2022). Climate-Tech to Watch: Sustainable Aviation Fuel. https://itif.org/publications/2022/10/17/climate-tech-to-watch-sustainable-aviation-fuel

Buchholz, N., Fehrm, B., Kaestner, L., Uhrenbacher, S., & Vesco, M. (2023). Study: How To Accelerate Aviation’s CO₂ Reduction | Aviation Week Network. https://aviationweek.com/air-transport/aircraft-propulsion/study-how-accelerate-aviations-co2-reduction 

Bullerdiek, N., Neuling, U., & Kaltschmitt, M. (2021). A GHG reduction obligation for sustainable aviation fuels (SAF) in the EU and in Germany. Journal of Air Transport Management, 92, 102020. https://doi.org/10.1016/j.jairtraman.2021.102020

EASA. (2025). Sustainable Aviation Fuels | EASA. https://www.easa.europa.eu/en/domains/environment/eaer/sustainable-aviation-fuels

European Commission. (n.d.). ReFuelEU Aviation. ReFuelEU Aviation - European Commission. https://transport.ec.europa.eu/transport-modes/air/environment/refueleu-aviation_en 

ICAO. (n.d.). LTAG Costs and Investments. ICAO. https://www.icao.int/environmental-protection/LTAG/Pages/LTAG-and-Fuels.aspx

ICAO. (n.d.). Sustainable Aviation Fuels. https://www.icao.int/environmental-protection/pages/SAF.aspx

IEA. (2025). Aviation. IEA. https://www.iea.org/energy-system/transport/aviation

IATA. (2024). IATA - Disappointingly Slow Growth in SAF Production. https://www.iata.org/en/pressroom/2024-releases/2024-12-10-03/

IATA. (2025). IATA Releases SAF Accounting and Reporting Methodology. https://www.iata.org/en/pressroom/2025-releases/2025-01-31-01/

Michaga, M. F. R., Michailos, S., Hughes, K. J., Ingham, D., & Pourkashanian, M. (2021). 10—Techno-economic and life cycle assessment review of sustainable aviation fuel produced via biomass gasification. In R. C. Ray (Ed.), Sustainable Biofuels (pp. 269–303). Academic Press. https://doi.org/10.1016/B978-0-12-820297-5.00012-8

O’Malley, J., & Baldino, C. (2024). Availability of biomass feedstocks in the European Union to meet the 2035 ReFuelEU Aviation SAF target. International Council on Clean Transportation. https://theicct.org/publication/low-risk-biomass-feedstocks-eu-refueleu-aug24/

Prussi, M., Lee, U., Wang, M., Malina, R., Valin, H., Taheripour, F., Velarde, C., Staples, M. D., Lonza, L., & Hileman, J. I. (2021). CORSIA: The first internationally adopted approach to calculate life-cycle GHG emissions for aviation fuels. Renewable and Sustainable Energy Reviews, 150, 111398. https://doi.org/10.1016/j.rser.2021.111398

Rojas-Michaga, M. F., Michailos, S., Cardozo, E., Akram, M., Hughes, K. J., Ingham, D., & Pourkashanian, M. (2023). Sustainable aviation fuel (SAF) production through power-to-liquid (PtL): A combined techno-economic and life cycle assessment. Energy Conversion and Management, 292, 117427. https://doi.org/10.1016/j.enconman.2023.117427

Shahriar, M. F., & Khanal, A. (2022). The current techno-economic, environmental, policy status and perspectives of sustainable aviation fuel (SAF). Fuel, 325, 124905. https://doi.org/10.1016/j.fuel.2022.124905 

Voigt, C., Kleine, J., Sauer, D., Moore, R. H., Bräuer, T., Le Clercq, P., Kaufmann, S., Scheibe, M., Jurkat-Witschas, T., Aigner, M., Bauder, U., Boose, Y., Borrmann, S., Crosbie, E., Diskin, G. S., DiGangi, J., Hahn, V., Heckl, C., Huber, F., … Anderson, B. E. (2021). Cleaner burning aviation fuels can reduce contrail cloudiness. Communications Earth & Environment, 2(1), 1–10. https://doi.org/10.1038/s43247-021-00174-y

Watson, M. J., Machado, P. G., da Silva, A. V., Saltar, Y., Ribeiro, C. O., Nascimento, C. A. O., & Dowling, A. W. (2024). Sustainable aviation fuel technologies, costs, emissions, policies, and markets: A critical review. Journal of Cleaner Production, 449, 141472. https://doi.org/10.1016/j.jclepro.2024.141472

World Economic Forum. (2021). Clean Skies for Tomorrow: Sustainable Aviation Fuels as a Pathway to Net-Zero Aviation. World Economic Forum. https://www3.weforum.org/docs/WEF_Clean_Skies_Tomorrow_SAF_Analytics_2020.pdf

Yoo, E., Lee, U., & Wang, M. (2022). Life-Cycle Greenhouse Gas Emissions of Sustainable Aviation Fuel through a Net-Zero Carbon Biofuel Plant Design. ACS Sustainable Chemistry & Engineering, 10(27), 8725–8732. https://doi.org/10.1021/acssuschemeng.2c00977

Zahid, I., Nazir, M. H., Chiang, K., Christo, F., & Ameen, M. (2024). Current outlook on sustainable feedstocks and processes for sustainable aviation fuel production. Current Opinion in Green and Sustainable Chemistry, 49, 100959. https://doi.org/10.1016/j.cogsc.2024.100959 

Credits

Lead Fellow

  • Heather Jones

Internal Reviewers

  • Christina Swanson
  • Emily Cassidy
  • Greenhouse gas quantity expressed relative to CO₂ with the same warming impact over 100 years, calculated by multiplying emissions by the 100-yr GWP for the emitted gases.

  • Greenhouse gas quantity expressed relative to CO with the same warming impact over 20 years, calculated by multiplying emissions by the 20-yr GWP for the emitted gases.

  • Reducing greenhouse gas concentrations in the atmosphere by preventing or reducing emissions.

  • The process of increasing the acidity of water or soil due to increased levels of certain air pollutants.

  • Benefits of climate solutions that extend beyond their ability to reduce emissions or store carbon (e.g., benefits to public health, water quality, biodiversity, advancing human rights).

  • The extent to which emissions reduction or carbon removal is above and beyond what would have occurred without implementing a particular action or solution.

  • An upper limit on solution adoption based on physical or technical constraints, not including economic or policy barriers. This level is unlikely to be reached and will not be exceeded.

  • The quantity and metric to measure implementation for a particular solution that is used as the reference unit for calculations within that solution.

  • Farming practices that work to create socially and ecologically sustainable food production.

  • Addition of trees and shrubs to crop or animal farming systems.

  • Spread out the cost of an asset over its useful lifetime.

  • A crop that live one year or less from planting to harvest; also called annual.

  • black carbon

  • Made from material of biological origin, such as plants, animals, or other organisms.

  • A renewable energy source generated from organic matter from plants and/or algae.

  • An energy source composed primarily of methane and CO that is produced by microorganisms when organic matter decomposes in the absence of oxygen.

  • Carbon stored in biological matter, including soil, plants, fungi, and plant products (e.g., wood, paper, biofuels). This carbon is sequestered from the atmosphere but can be released through decomposition or burning.

  • Living or dead renewable matter from plants or animals, not including organic material transformed into fossil fuels. Peat, in early decay stages, is partially renewable biomass.

  • A type of carbon sequestration that captures carbon from CO via photosynthesis and stores it in soils, sediments, and biomass, distinct from sequestration through chemical or industrial pathways.

  • A climate pollutant, also called soot, produced from incomplete combustion of organic matter, either naturally (wildfires) or from human activities (biomass or fossil fuel burning).

  • High-latitude (>50°N or >50°S) climate regions characterized by short growing seasons and cold temperatures.

  • The components of a building that physically separate the indoors from the outdoor environment.

  • Businesses involved in the sale and/or distribution of solution-related equipment and technology, and businesses that want to support adoption of the solution.

  • A chemical reaction involving heating a solid to a high temperature: to make cement clinker, limestone is calcined into lime in a process that requires high heat and produces CO.

  • A four-wheeled passenger vehicle.

  • Technologies that collect CO before it enters the atmosphere, preventing emissions at their source. Collected CO can be used onsite or in new products, or stored long term to prevent release.

  • A greenhouse gas that is naturally found in the atmosphere. Its atmospheric concentration has been increasing due to human activities, leading to warming and climate impacts.

  • Total GHG emissions resulting from a particular action, material, technology, or sector.

  • Amount of GHG emissions released per activity or unit of production. 

  • A marketplace where carbon credits are purchased and sold. One carbon credit represents activities that avoid, reduce, or remove one metric ton of GHG emissions.

  • A colorless, odorless gas released during the incomplete combustion of fuels containing carbon. Carbon monoxide can harm health and be fatal at high concentrations.

  • Activities or technologies that pull CO out of the atmosphere, including enhancing natural carbon sinks and deploying engineered sinks.

  • Long-term storage of carbon in soils, sediment, biomass, oceans, and geologic formations after removal of CO from the atmosphere or CO capture from industrial and power generation processes.

  • carbon capture and storage

  • carbon capture, utilization, and storage

  • A binding ingredient in concrete responsible for most of concrete’s life-cycle emissions. Cement is made primarily of clinker mixed with other mineral components.

  • methane

  • Gases or particles that have a planet-warming effect when released to the atmosphere. Some climate pollutants also cause other forms of environmental damage.

  • A binding ingredient in cement responsible for most of the life-cycle emissions from cement and concrete production.

  • carbon monoxide

  • Neighbors, volunteer organizations, hobbyists and interest groups, online communities, early adopters, individuals sharing a home, and private citizens seeking to support the solution.

  • A solution that potentially lowers the benefit of another solution through reduced effectiveness, higher costs, reduced or delayed adoption, or diminished global climate impact.

  • A farming system that combines reduced tillage, cover crops, and crop rotations.

  • carbon dioxide

  • A  measure standardizing the warming effects of greenhouse gases relative to CO. CO-eq is calculated as quantity (metric tons) of a particular gas multiplied by its GWP.

  • carbon dioxide equivalent

  • The process of cutting greenhouse gas emissions (primarily CO) from a particular sector or activity.

  • A solution that works slower than gradual solutions and is expected to take longer to reach its full potential.

  • Microbial conversion of nitrate into inert nitrogen gas under low-oxygen conditions, which produces the greenhouse gas nitrous oxide as an intermediate compound.

  • Greenhouse gas emissions produced as a direct result of the use of a technology or practice.

  • Ability of a solution to reduce emissions or remove carbon, expressed in CO-eq per installed adoption unit. Effectiveness is quantified per year when the adoption unit is cumulative over time.

  • Greenhouse gas emissions accrued over the lifetime of a material or product, including as it is produced, transported, used, and disposed of.

  • Solutions that work faster than gradual solutions, front-loading their impact in the near term.

  • Methane produced by microbes in the digestive tracts of ruminant livestock, such as cattle, sheep and goats.

  • environmental, social, and governance

  • exchange-traded fund

  • A process triggered by an overabundance of nutrients in water, particularly nitrogen and phosphorus, that stimulates excessive plant and algae growth and can harm aquatic organisms.

  • The scientific literature that supports our assessment of a solution's effectiveness.

  • A group of human-made molecules that contain fluorine atoms. They are potent greenhouse gases with GWPs that can be hundreds to thousands times higher than CO.

  • food loss and waste

  • Food discarded during pre-consumer supply chain stages, including production, harvest, and processing.

  • Food discarded at the retail and consumer stages of the supply chain.

  • Combustible materials found in Earth's crust that can be burned for energy, including oil, natural gas, and coal. They are formed from decayed organisms through prehistoric geological processes.

  • greenhouse gas

  • gigajoule or billion joules

  • The glass layers or panes in a window.

  • A measure of how effectively a gas traps heat in the atmosphere relative to CO. GWP converts greenhouse gases into CO-eq emissions based on their 20- or 100-year impacts.

  • A solution that has a steady impact so that the cumulative effect over time builds as a straight line. Most climate solutions fall into this category.

  • A gas that traps heat in the atmosphere, contributing to climate change.

  • metric gigatons or billion metric tons

  • global warming potential

  • hectare

  • household air pollution

  • Number of years a person is expected to live without disability or other limitations that restrict basic functioning and activity.

  • A unit of land area comprising 10,000 square meters, roughly equal to 2.5 acres.

  • hydrofluorocarbon

  • hydrofluoroolefin

  • Particles and gases released from use of polluting fuels and technologies such as biomass cookstoves that cause poor air quality in and around the home.

  • Organic compounds that contain hydrogen and carbon.

  • Human-made F-gases that contain hydrogen, fluorine, and carbon. They typically have short atmospheric lifetimes and GWPs hundreds or thousands times higher than CO

  • Human-made F-gases that contain hydrogen, fluorine, and carbon, with at least one double bond. They have low GWPs and can be climate-friendly alternatives to HFC refrigerants.

  • internal combustion engine

  • Greenhouse gas emissions produced as a result of a technology or practice but not directly from its use.

  • Device used to power vehicles by the intake, compression, combustion, and exhaust of fuel that drives moving parts.

  • The annual discount rate that balances net cash flows for a project over time. Also called IRR, internal rate of return is used to estimate profitability of potential investments.

  • Individuals or institutions willing to lend money in search of a return on their investment.

  • internal rate of return

  • A measure of energy

  • International agreement adopted in 2016 to phase down the use of high-GWP HFC F-gases over the time frame 2019–2047.

  • A measure of energy equivalent to the energy delivered by 1,000 watts of power over one hour.

  • kiloton or one thousand metric tons

  • kilowatt-hour

  • A land-holding system, e.g. ownership, leasing, or renting. Secure land tenure means farmers or other land users will maintain access to and use of the land in future years.

  • Gases, mainly methane and CO, created by the decomposition of organic matter in the absence of oxygen.

  • leak detection and repair

  • Regular monitoring for fugitive methane leaks throughout oil and gas, coal, and landfill sector infrastructure and the modification or replacement of leaking equipment.

  • Relocation of emissions-causing activities outside of a mitigation project area rather than a true reduction in emissions.

  • The rate at which solution costs decrease as adoption increases, based on production efficiencies, technological improvements, or other factors.

  • Percent decrease in costs per doubling of adoption.

  • landfill gas

  • Greenhouse gas emissions from the sourcing, production, use, and disposal of a technology or practice.

  • low- and middle-income countries

  • liquefied petroleum gas

  • A measure of the amount of light produced by a light source per energy input.

  • square meter kelvins per watt (a measure of thermal resistance, also called R-value)

  • marginal abatement cost curve

  • Livestock grazing practices that strategically manage livestock density, grazing intensity, and timing. Also called improved grazing, these practices have environmental, soil health, and climate benefits, including enhanced soil carbon sequestration.

  • A tool to measure and compare the financial cost and abatement benefit of individual actions based on the initial and operating costs, revenue, and emission reduction potential.

  • A greenhouse gas with a short lifetime and high GWP that can be produced through a variety of mechanisms including the breakdown of organic matter.

  • A measure of mass equivalent to 1,000 kilograms (~2,200 lbs).

  • million hectares

  • Soils mostly composed of inorganic materials formed through the breakdown of rocks. Most soils are mineral soils, and they generally have less than 20% organic matter by weight.

  • A localized electricity system that independently generates and distributes power. Typically serving limited geographic areas, mini-grids can operate in isolation or interconnected with the main grid.

  • Reducing the concentration of greenhouse gases in the atmosphere by cutting emissions or removing CO.

  • Percent of trips made by different passenger and freight transportation modes.

  • megaton or million metric tons

  • A commitment from a country to reduce national emissions and/or sequester carbon in alignment with global climate goals under the Paris Agreement, including plans for adapting to climate impacts.

  • A gaseous form of hydrocarbons consisting mainly of methane.

  • Chemicals found in nature that are used for cooling and heating, such as CO, ammonia, and some hydrocarbons. They have low GWPs and are ozone friendly, making them climate-friendly refrigerants.

  • Microbial conversion of ammonia or ammonium to nitrite and then to nitrate under aerobic conditions.

  • A group of air pollutant molecules composed of nitrogen and oxygen, including NO and NO.

  • A greenhouse gas produced during fossil fuel combustion and agricultural and industrial processes. NO is hundreds of times more potent than CO at trapping atmospheric heat, and it depletes stratospheric ozone.

  • Social welfare organizations, civic leagues, social clubs, labor organizations, business associations, and other not-for-profit organizations.

  • A material or energy source that relies on resources that are finite or not naturally replenished at the rate of consumption, including fossil fuels like coal, oil, and natural gas.

  • nitrogen oxides

  • nitrous oxide

  • The process of increasing the acidity of seawater, primarily caused by absorption of CO from the atmosphere.

  • An agreement between a seller who will produce future goods and a purchaser who commits to buying them, often used as project financing for producers prior to manufacturing.

  • Productive use of wet or rewetted peatlands that does not disturb the peat layer, such as for hunting, gathering, and growing wetland-adapted crops for food, fiber, and energy.

  • A measure of transporting one passenger over a distance of one kilometer.

  • The longevity of any greenhouse gas emission reductions or removals. Solution impacts are considered permanent if the risk of reversing the positive climate impacts is low within 100 years.

  • A mixture of hydrocarbons, small amounts of other organic compounds, and trace amounts of metals used to produce products such as fuels or plastics.

  • Private, national, or multilateral organizations dedicated to providing aid through in-kind or financial donations.

  • An atmospheric reaction among sunlight, VOCs, and nitrogen oxide that leads to ground-level ozone formation. Ground-level ozone, a component of smog, harms human health and the environment.

  • passenger kilometer

  • particulate matter

  • Particulate matter 2.5 micrometers or less in diameter that can harm human health when inhaled.

  • Elected officials and their staff, bureaucrats, civil servants, regulators, attorneys, and government affairs professionals.

  • System in a vehicle that generates power and delivers it to the wheels. It typically includes an engine and/or motor, transmission, driveshaft, and differential.

  • People who most directly interface with a solution and/or determine whether the solution is used and/or available. 

  • The process of converting inorganic matter, including carbon dioxide, into organic matter (biomass), primarily by photosynthetic organisms such as plants and algae.

  • Defined by the International Union for the Conservation of Nature as: "A clearly defined geographical space, recognised, dedicated and managed, through legal or other effective means, to achieve the long-term conservation of nature with associated ecosystem services and cultural values". References to PAs here also include other effective area-based conservation measures defined by the IUCN. 

  • Very large or small numbers are formatted in scientific notation. A positive exponent multiplies the number by powers of ten; a negative exponent divides the number by powers of ten.

  • Small-scale family farmers and other food producers, often with limited resources, usually in the tropics. The average size of a smallholder farm is two hectares (about five acres).

  • soil organic carbon

  • Carbon stored in soils, including both organic (from decomposing plants and microbes) and inorganic (from carbonate-containing minerals).

  • Carbon stored in soils in organic forms (from decomposing plants and microbes). Soil organic carbon makes up roughly half of soil organic matter by weight.

  • Biologically derived matter in soils, including living, dead, and decayed plant and microbial tissues. Soil organic matter is roughly half carbon on a dry-weight basis.

  • soil organic matter

  • sulfur oxides

  • sulfur dioxide

  • The rate at which a climate solution physically affects the atmosphere after being deployed. At Project Drawdown, we use three categories: emergency brake (fastest impact), gradual, or delayed (slowest impact).

  • Climate regions between latitudes 23.4° to 35° above and below the equator characterized by warm summers and mild winters.

  • A polluting gas produced primarily from burning fossil fuels and industrial processes that directly harms the environment and human health.

  • A group of gases containing sulfur and oxygen that predominantly come from burning fossil fuels. They contribute to air pollution, acid rain, and respiratory health issues.

  • Processes, people, and resources involved in producing and delivering a product from supplier to end customer, including material acquisition.

  • metric tons

  • Technology developers, including founders, designers, inventors, R&D staff, and creators seeking to overcome technical or practical challenges.

  • Climate regions between 35° to 50° above and below the equator characterized by moderate mean annual temperatures and distinct seasons, with warm summers and cold winters.

  • A measure of how well a material prevents heat flow, often called R-value or RSI-value for insulation. A higher R-value means better thermal performance.

  • Individuals with an established audience for their work, including public figures, experts, journalists, and educators.

  • Low-latitude (23.4°S to 23.4°N) climate regions near the Equator characterized by year-round high temperatures and distinct wet and dry seasons.

  • United Nations

  • Self-propelled machine for transporting passengers or freight on roads.

  • A measure of one vehicle traveling a distance of one kilometer.

  • vehicle kilometer

  • volatile organic compound

  • Gases made of organic, carbon-based molecules that are readily released into the air from other solid or liquid materials. Some VOCs are greenhouse gases or can harm human health.

  • watt

  • A measure of power equal to one joule per second.

  • A subset of forest ecosystems that may have sparser canopy cover,  smaller-stature trees, and/or trees characterized by basal branching rather than a single main stem.

  • year