Following the success of flight trials by Continental Airlines, KLM, Air New Zealand, Japan Airlines, and others, biofuels are now certified as safe and appropriate for commercial use. This was a very delicate process and a political balancing act, since safety is always a big issue.

Certified bio jet fuel is now recognized worldwide as an absolutely safe fuel to fly with it. Up in the air you have a freezing point of —54°C so the jet fuel must remain liquid at very low temperatures. Also, at 10 000 feet you have three dimensions instead of two here on the ground. If your car engine stops working you just get out of your car. With three dimensions it is slightly different!

The aviation industry has been working closely with fuel specification bodies, such as the American Society for Testing and Materials (ASTM) International and the UK Defence Standardization agency. The approval process had three parts: the

test program, the original equipment manufacturer internal review, and a deter­mination by the specification body as to the correct specification for the fuel. The approval process has looked at a minimum of 11 key properties, including energy density, freezing point, appearance, composition, volatility, fluidity, and many other characteristics, which would make it fit for aviation use. A 50/50 blend of biofuels mixed with Jet A-1 fuel has been certified in 2011. Due to recent advances in research and technology, aviation biofuel might be available for commercial use within 2-3 years, once the airlines can buy sufficient quantities of feedstock.

Now that biofuels for aviation are a confirmed viable option and the certification process has been concluded, the biggest challenges is cultivating the required quantity of feedstock. The worldwide aviation industry consumes some 1.5-1.7 billion bar­rels of Jet A-1 annually (about 250 billion liters or 65 billion gallons). Analysis suggests that a viable market for biofuels can be maintained when as little as 1% of the world’s jet fuel supply is substituted by a biofuel (or, put another way, 10% of the world’s aircraft fleet is running on a mix of 10% biofuel and 90% Jet A-1). Thus, when will the industry be able to reach that point? I think it will not happen before 2015. Some parts of the industry are aiming to operate fleet using 25% biofuel by 2025, which would be increased to 30% by 2030. However, it is necessary to produce sustainable feedstocks on massive commercial-scale quan­tities for these targets to be reached.

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astm

In September 2009, a new jet fuel approval framework for alternative fuels (ASTM D7566) was announced, along with initial approvals for using certification goals for 2011 to include the approval of Bio-SPK fuels from oil seed plants such as Camelina and Jatropha. The criteria for fuel approval and also for moving forward with the approval of new process types (fermentation, pyrolysis) along with how to engage new suppliers in the approval process are part of this new framework.

The aviation community sees the introduction of renewable jet fuel alternatives as an essential component for meeting its environmental objectives, including achieving carbon-neutral growth in the next decade. The potential benefits go beyond greenhouse gas emissions, with alternative aviation fuels showing promise in contributing to the airlines’ efforts to minimize small particulate matter emissions affecting local air quality.

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