FAME: fuelling the safety debate16 February 2012
Contamination of jet turbine fuel by fatty acid methyl esters (FAME) is a growing concern for the aerospace industry. A report due for publication by the Energy Institute later in 2012 is expected to recommend levels of FAME in aviation fuel be significantly increased. But are safety screening and testing techniques sufficiently advanced, and where does accountability lie? Julian Turner reports.
In 2008, the British Government ruled that all petrol and diesel sold on forecourts must contain at least 2.5% biofuel. On the surface, this initiative - and others like it issued by EU member states under the Renewable Energy Directive - was of interest only to the automotive industry.
However, the biofuel contained fatty acid methyl esters, or FAME, and this was to have unseen safety implications for airline operators.
The controversy concerns the potential contamination of jet turbine fuel by FAME. While the automotive world accepted FAME in diesel and simple oxygenates, like ethanol in gasoline, the aviation industry ruled that only hydrocarbon fuels would be permitted as renewable fuels. Stefan Ebert, project certification manager propulsion at the European Aviation Safety Agency (EASA), explains.
"FAME-blended fuels do not meet the requirements of globally recognised fuel specifications such as UK MoD Def Stan 91-91 or US ASTM D1655 in terms of combustion properties, energy content and material compatibility," he says. "Only small amounts of FAME may be accepted to allow further operation of the fuel distribution system (ground handling).
"FAME is not an approved blending component for Jet A-1 fuel. It is a low-level undesirable material, or contaminant."
Supply chain pressures: the risk of contamination
Unfortunately, diesel and jet fuel share distribution systems, increasing the likelihood of cross-contamination at multiple points in the supply chain. These include refineries, terminals, fuel-blending distribution sites, fuel tank storage facilities and, most importantly, during the shipping of fuel and its movement through pipelines.
FAME is a highly surface-active material that can adhere to pipe and tank walls as the diesel passes through. Small amounts of diesel containing FAME can therefore remain within distribution manifolds, tanks, vehicles or pipelines and potentially pollute jet fuel transported through the same supply system.
Consequences can be grave. In an article published by the Energy Institute (EI) in December 2011, Mike Farmery, global fuel and quality manager at Shell Aviation, emphasised the need for strict, industry-wide safety standards to counter the threat of contamination and issued a stark warning about the risks of non-compliance.
"Although fuel quality has a fantastic track record, the potential for catastrophe was highlighted in April 2010 when contamination in the fuel caused the throttles on the two engines on Cathay Pacific flight CX 780 to stick," Farmery said. "If it wasn't for the skill of the Cathay pilot and a long runway at Hong Kong, many could have died."
"The world changed with the introduction of FAME in diesel," he stated. "Instinctively, the aero engine OEMs put an immediate cap on FAME carryover into jet fuel at 5mg/kg (the minimum level of detection at the time) until a better understanding of the effects of FAME on engine performance could be determined.
"The number of incidents over the past three years has been impressively low, but some supply chains are on a knife-edge."
Testing times: new fuel-screening techniques
Now, this crucial cap on FAME levels in jet fuel could be about to change with the publication of an eagerly-awaited report from the EI's joint industry project (JIP).
Since 1965, the EI has provided technical publications and guidance to facilitate the safe and efficient handling of aviation fuel at international airports. The equipment standards in particular are followed worldwide by manufacturers and adopted by international airlines, major and national oil companies, into-plane companies and aviation fuel hydrant operators.
The culmination of months of exhaustive research into the effects of FAME on the hardware and performance of aero engines - and backed by engine and airframe manufacturers - the forthcoming report it is expected to recommend that quantities of the biofuel be increased to 100mg/kg, or 20 times the current level.
"It is expected that the increase in the FAME level will be implemented in one of the next revisions of Def Stan 91-91 and ASTM D1655," says Ebert. "These specifications cover all relevant aspects necessary for a safe operation of aircraft and its engines such as thermal stability, volatility, density, viscosity, freezing point, energy content and lubricity."
Testing and screening techniques have also had to catch up. SetaAnalytics has pioneered a rapid screening test to detect levels of FAME contamination. The FIJI - FAME in Jet Instrument gives a quick indication of FAME levels that may necessitate further investigation to ensure a safe product is delivered at wing. Tests require a sample of less than 50ml and typically take less than 20 minutes.
A key advantage over current analytical methods is FIJI's ability to detect all types of FAME. More than 1,000 tests have been carried out on jet fuel samples from refineries, storage, distribution facilities and airports globally. The development of FIJI has led to the introduction of a new oil industry test method IP 583 - the first method for the Rapid Screening of FAME in JET (AVTUR).
Joint enterprise: the future of biofuel
Since 1960, the aviation industry has reduced fuel consumption, and hence CO2 emissions, by 70% per passenger km. Half a century on, it is busy responding to the challenge of finding and safely exploiting alternative fuel sources.
On 6 October 2011, a Thomson Airways Boeing 757-200 carried 232 passengers from Birmingham Airport, UK, to Arrecife in Spain using sustainable biofuels blend in one engine. United Airlines is negotiating the purchase of 20 million gallons of jet fuel a year, derived exclusively from algae oil. HEFA blended fuels have been used successfully for passenger flights by KLM and Lufthansa.
"It is now possible to fly with jet fuel containing up to 50% kerosene made from natural gas, coal or biomass via the Fischer-Tropsch (FT) process or up to 50% hydrogenated esters or fatty acids (HEFA). This is particularly impressive given the highly conservative nature of the aviation industry," said Farmery, before sounding a note of caution.
"Although airlines can now, in principle, fly on renewable jet fuel, many don't believe we have found the optimum combination of feedstock and process yet," he added.
FAME is a contaminant whose presence in - and influence on - jet fuel is being weighed against its potential environmental benefits, but what of the safety issues surrounding other biofuels?
As yet they cannot be relied upon to operate as reliably as traditional fuels under the same conditions. Jet A fuel, one of the standard aviation fuels, has a stable energy content and a low freeze point, meaning it can perform at the very low temperatures tolerated by high-flying aircraft. Jet A fuel also burns consistently, which means it provides a safe fuel source for long flights. The same cannot be said for biofuels.
"EASA is participating in the UK AFC and ASTM D02.J aviation fuel committees, which are international industry-based consensus organisations. Fuels or fuel-blending components from renewable sources that are not yet addressed in the jet fuel specifications have to be tested and reviewed. EASA is aware of the ongoing activities and may influence the process in case of safety concerns," Ebert said.
Farmery was also keen to emphasise that all industry stakeholders, from engine and aircraft manufacturers to operator airlines and official industry bodies, have a vested interest in taking responsibility for fuel safety.
"The industry, led by IATA, the Air Transport Association (ATA) and Joint Inspection Group (JIG) has been busy in response to the [Cathay Pacific] incident and there is now a great deal of work underway to produce a comprehensive manual under the jurisdiction of the International Civil Aviation Organisation (ICAO) to cover all aspects of aviation fuel supply," he said.
"Everyone involved in supplying aviation fuel from refinery to aircraft has to work to the same, agreed industry standards."