Regulate Jet Fuel’s Aromatics Content to Reduce Non-CO2 Impacts of Aviation, says Dutch Report
by Christopher Surgenor (GreenAir Online) Although research is ongoing, it is widely accepted aviation’s contribution to global warming goes well beyond that caused by carbon dioxide emissions alone. One of the main non-CO2 impacts is the net warming effect from the formation of contrails and contrail cirrus caused when aircraft engines emit particulates (soot) at altitude in ice-supersaturated regions. The main culprit is the aromatic content of jet fuel, and fuels with a higher concentration of aromatics and especially naphthalene, a bicyclic aromatic compound, cause higher particulate emissions because aromatics burn slower than other hydrocarbons. Sustainable aviation fuels, on the hand, have negligible concentrations of aromatics because they are hydrotreated. Their use therefore could have beneficial consequences, but they are currently only permitted in blends up to a maximum of 50% with conventional fossil jet fuel so the aromatics issue remains. A report by CE Delft for the Dutch government proposes the aromatic content of jet fuel be monitored or controlled within the proposed ReFuelEU Aviation SAF regulation in such a way that it is decreased to ensure the non-CO2 climate impact of aviation is reduced.
A report on non-CO2 impacts by European aviation agency EASA in 2020 identified lowering the aromatic content of jet fuel as a way of reducing the sector’s climate impact and analysed several policy options but concluded current uncertainty and lack of information about aromatic content was a significant barrier to monitoring the effectiveness of such a policy.
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The requirement for a minimum 8% content of aromatics has historically been applied for safety considerations, stemming from the role aromatics play in the swell of sealings in the aircraft fuel system. However, the report found contradicting opinions on this, with several modern aircraft and engine types having sealing materials that do not require aromatics for the swell function, and research into new materials is ongoing.
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Airlines might be interested because jet fuel with lower aromatic content has higher energy density and therefore slightly less jet fuel is needed for flying a given distance, and it also reduces their environmental footprint, but likely it would come at a higher fuel price. READ MORE
Potential for reducing aviation non-CO2 emissions through cleaner jet fuel (CE Delft)
Updated analysis of the non-CO2 climate impacts of aviation and potential policy measures pursuant to EU Emissions Trading System Directive Article 30(4) (European Union Aviation Safety Agency)
