Bombardier’s Global 6000 is by no means an unfamiliar sight at Geneva, but there was something different about its arrival on Saturday. The aircraft was the first of several that flew in from TAG Farnborough, near London, following a conference organized by the Sustainable Alternative Jet Fuels Coalition, a cross-industry body which has published a guide to the use of SAJF – sustainable alternative jet fuel. All of the follow-on flights to Geneva used sustainable fuel.

“It’s truly a historic day,” David Coleal, Bombardier president and chairman of the General Aviation Manufacturers Association’s environment committee, told attendees at Farnborough.

“At the last count, more than half the turbine aircraft that are on display at EBACE this year are arriving with blend of SAJF and Jet A-1 ,” he added. “It’s a huge achievement, and it demonstrates that it can be done: that 20,000 business aircraft in service globally can safely fly on SAJF today.”

But the route the industry will have to take if it is to reach the ambitious goals it set for itself in 2009 - which include a 50% reduction in carbon emissions from the sector by 2050 - is by no means an easy one to follow. The introduction of SAJF raises complex and intertwined questions that cover economic, logistic, scientific and operational areas. Yet, industry leaders say, what matters most at this stage is that everyone agrees on the need to head in the same direction.

“SAJF faces several challenges,” Coleal says. “Production must increase beyond the handful of refineries we now have. We need to improve distribution and availability, while at the same time expanding awareness and encouraging adoption by our community. Events like today are the bedrock of this effort and the start of our quest.”

“We have four pillars that we see as [the necessary means to reach] our goals,” International Business Aviation Council director general Kurt Edwards told the Farnborough conference. “The first is improved operations - we’re all working on trying to be as light and flying as directly as possible. You’ve got air-traffic management infrastructure modernization. And then there’s technology - which includes not just what we can do to make aircraft and engines more efficient, it also includes SAJF. And the fourth pillar, when it’s needed, is market-based measures.”

The pillars reflect the different complicating elements of the sustainable jet fuel concept. For SAJF to be a viable option, it has to work in existing engines without requiring modifications. There are different processes by which the synthetic fuel is produced, each of which can use different feedstocks from which the fuel is derived. Each combination of process and feedstock must meet ASTM technical and certification requirements equivalent to Jet A-1 to be used as a drop-in, like-for-like replacement for standard fossil fuel.

Yet even then there are differences, particularly around aromatics, which may affect seals in some engines. While a small number of flights have been carried out with 100% SAJF, for everyday use, each certified SAJF has to be blended with Jet A-1 in ratios that, additionally, have to be certified. Some SAJFs are approved for a 50:50 mix with Jet A-1, while others can only be used in 30:70 or 10:90 blends.

This means that there is no one single SAJF product: rather, the term covers a multitude of different synthetic fuels which are approved for use only when blended with conventional fuel.

Despite the multiple production pathways, the supply of SAJF is presently very limited. There are few economies of scale, and the certification costs, while one-off, are significant. As a result, SAJF is considerably more expensive than standard fuel - and that higher price is a barrier to increased adoption.

“At the present time, we’re seeing prices - on a blended basis, dependent upon the blend ratio - of roughly three times the price of normal jet fuel before taxes,” Keith Sawyer, alternative fuels manager at Avfuel Corporation, told the Farnborough conference. He was referring to U.S. prices: Tom Parsons, biojet commercial development manager for AirBP, said the equivalent price differentials were “at least that” in Europe.

“There are reasons why it’s more expensive,” Parsons continued. “You have less available feedstock, and you’re competing against something that can just be pulled out of the ground. I think the focus needs to be about ensuring sustainable supply of feedstock, and then investing in the capacity to produce it.”