Modern jet aircraft use a petroleum-based fuel commonly referred to as "Jet A" or "Jet A-1." Alternative fuel is fuel that is not derived from petroleum. Alternative fuels can be classified into three categories; synthetics, biofuels, and others.
Synthetics: Synthetic kerosene can be made from coal, natural gas, or other hydrocarbon resources and can be produced by first turning the resource into gases, which are then recombined to form hydrocarbon liquids. Synthetic kerosene can be tailored to have similar properties to petroleum kerosene, thus can be thought of as a "drop-in" replacement. Synthetic kerosene from coal is currently approved for aviation use as a supplement to petroleum-based jet fuel and is anticipated to be approved for use as a total replacement. Synthetic fuel production is an energy intensive process that, in the absence of proven methods to capture and sequester, produces significantly higher CO2 emissions than the production of petroleum-derived fuel.
Biofuels: Biofuel can be made from the oils contained in crops/feedstock (e.g. soybeans and canola seeds) to produce petroleum-like oil that can be transformed into fuel similar to diesel fuel (i.e. biodiesel.) An additional processing step needed to transform biodiesel into biojet fuel is currently being evaluated for its performance properties. This is a renewable fuel, but conventional crops/feedstock require significant quantities of arable land to produce enough bio fuels to supply scaleable and sustainable fuel needs. Other feedstocks with much higher oil yields (e.g. algae) are currently being evaluated.
Other: Hydrogen, natural gas, ethanol, methanol, and propane (LPG) have been considered for alternative aviation fuels. All represent significant challenges and would require new aircraft and fuel delivery systems.
Hydrogen and natural gas must be used in their liquid form, which requires storage at extremely cold temperatures. Hydrogen burns cleanly, but its production is very energy intensive and it emits large quantities of water vapor with uncertain effects on cloud formation and the atmosphere.
Aviation and Global Climate Change in the 21st Century (April 2009)
The authors that had assessed aviation's contribution to climate change to be 3% in the Fourth Assessment Reports (AR4) is now estimating aviation's contribution to climate change to be 3.5% without cirrus and 4.9% with cirrus.
The Intergovernmental Panel on Climate Change (IPCC) states in its 1999 report on aviation and climate change that airplanes emit 2% of man-made CO2 in 1992 and is expected to grow to 3% in 2050. The Aviation and Global Climate Change in the 21st Century report contains CO2 data that indicates aviation remains 2% of anthropogenic CO2.
Aviation is the only industry that has asked the IPCC for a total assessment on climate change. The original assessment done in 1999 used RF as a way to assess the impact beyond CO2. Given the considerable uncertainty of the other gases, particularly those like aviation-induced cloudiness (AIC) that is unique to aviation, a more direct and understood comparison of aviation to other anthropogenic actives is better done via CO2.
TIACA, however, will continue to monitor what effects other gases (NOx, H2O vapour, contrails, AIC, sulphate particles, and soot particles) have on climate change and as more is understood what these effects are, we will be in a better position to correctly address how aviation can reduce its impact on the environment. More...
This section features current policy initiatives on which TIACA or its members may wish to comment, or at least be informed, given the potential impact on member operations. It will be updated as developments warrant.
The Future of Aviation Advisory Committee (FAAC) issued a series of recommendations to the Secretary of Transportation, calling for U.S. support for sustainable alternative aviation fuels, development and implementation of the NextGen air traffic management system, and an international approach to aviation carbon emissions.
The International Food Policy Research Institute has issued a study assessing global trade and the environmental impact of the EU biofuels mandate. The report finds first-generation biofuels achieve emissions reductions, and that trade liberalization would result in greater emissions reductions. For the full report, click here.
The U.S. Government Accountability Office (GAO) has issued a report analyzing the impact of increased biofuels production on U.S. greenhouse gas emissions, the environment, and agriculture. The report recommends that EPA assess the lifecycle impact of increased biofuels production, and calls for a coordinated approach by EPA and the departments of Agriculture and Energy.
IATA's 2008 report on Alternative Fuels. This report outlines IATA's work on alternative fuels and also describes its plans for the future.
A new report compares the greenhouse gas emissions of several aviation alternative fuels, based on a life-cycle analysis. Among other things, the report concludes that few biofuels have zero life-cycle emissions, and that life-cycle GHG emissions are only one of many considerations that should be used to evaluate feasibility and sustainability of alternative fuels.
This document describes the Copenhagen process and ongoing airline industry environmental efforts. IATA details its recommended policy approach in Copenhagen with an aim towards achieving carbon-neutral growth in 2020. The document also includes key principles that need to be taken into account for a global approach towards aviation within the Copenhagen process.
Op-ed by U.S. Congressman Costello entitled, "Aviation sector leads travel industry on energy efficiency". This op-ed discusses the progress made by the aviaiton industry on energy efficiency. It also outlines the importance of aviation emissions and the work that the industry is undertaking in fuel efficiency.
TIACA commissioned a report by Cranfield University in the UK that looks at: air transports existing contribution to global CO2 emissions, operational and regulatory constraints, future global CO2 emissions scenarios, investment in greater fuel efficiency in the future, the nature of the air cargo network and its effect on the industry's fuel efficiency and the role of air cargo in developing country exports.
Q. Why biofuel? Extracting and burning fossil fuels increases the amount of CO2 in the atmosphere.
A. Biofuels are the only fuel type where the source (a plant) absorbs CO2 from the atmosphere, helping to offset the emissions produced when they are consumed. Since biofuels are produced from plant materials they come from a renewable biological resource as compared to fossil fuels.
Q. Are all biofuels equal?
A. No. Many people are familiar with ethanol and biodiesel. These biofuels are primarily derived from corn and soybeans at present. But corn and soybeans are staple food crops and require large amounts of land and resources. This makes them unsustainable sources for biofuel. Sustainable biofuels don't compete with food resources; they require minimal land, water and energy to produce, and they provide economic value to the communities where they're grown.
Q. Which sustainable biofuels appear most promising?
A. It's unlikely that the demand for alternative fuels will be met by a single biofuel plant source, which makes a portfolio of solutions the best approach. Within this portfolio, examples of promising plant sources that meet the criteria for sustainability include algae, halophytes or other saline grasses, jatropha and non-food cellulose.
Q. In addition to biofuels, are there other solution(s) being looked at to reduce CO2 emission?
A. Yes. Improvements to the Air Traffic Management (ATM) system can help reduce CO2 emission. Flight delays are not only inconvenient, but they also waste fuel and increase emissions. Reducing every flight by just one minute would prevent 4.8 million tons of CO2 emissions each year. Aircraft manufacturers, airlines, airports, and civil aviation authorities are working together to demonstrate, develop and implement operational improvements to increase efficiency and reduce congestion, noise and emissions.