EU urged to cut emissions from aviation faster – and address the aromatics problem
Ciarán Cuffe, a Green MEP who is shadow rapporteur for the ReFuelEU Aviation file in the European Parliament’s transport committee, has called for the EU’s “clean” aviation fuels law to be amended to include non-CO2 effects. This includes the release of soot and harmful gases, including sulphur and nitrogen oxide, as well as water vapour, from jet engines. The EU’s proposed green aviation law overlooks the true climate cost of flying, with the non-CO2 effects of air travel producing 2-4 times the impact of CO2 emissions. He says it is not credible to delay by another decade and rely solely on voluntary industry efforts. This hasn’t worked up until now, and it won’t work in the future. Some of the non-CO2 impacts are due to aromatics in the fuel (compounds like propyl benzene, tetralin and p-xylene). So there are demands to reduce the amount of these, and sulphur content, in jet fuel. However these aromatics are important in current jet engine design, as they help swell seals and improve flow. If the industry goes for more novel fuels in future, these do not contain aromatics. So either aromatics will have to be added to the fuels, to protect the engines – or engines will have to be adapted.
EU urged to cut emissions from aviation faster than planned
29th April 2022 (Edie)
The EU’s proposed green aviation law overlooks the true climate cost of flying, with the non-CO2 effects of air travel producing two to four times the impact of carbon emissions, a Green MEP has said.
Ciarán Cuffe, a Green MEP who is shadow rapporteur for the ReFuelEU Aviation file in the European Parliament’s transport committee, has called for the EU’s clean aviation fuels law to be amended to include so-called non-CO2 effects. This includes the release of soot and harmful gases, including sulphur and nitrogen oxide, as well as water vapour, from jet engines.
At high altitudes, these emissions can cause the formation of contrails, which have a net warming effect much larger than CO2, according to a 2020 EU study.The emissions can also damage human health, which is of particular concern to those living in the vicinity of airports.
“We know that the non-CO2 effects of aviation represent two-thirds of the sector’s overall climate impact, but it remains unregulated,” said Cuffe.
“It’s not credible to delay by another decade and rely solely on voluntary industry efforts. This hasn’t worked up until now, and it won’t work in the future,” he added.
The Irish MEP has tabled an amendment mandating a progressive reduction of the aromatic and sulphur content of aviation fuels, two elements responsible for much of the non-CO2 pollution released by planes.
Aircraft function impacted
Despite the climate and health impacts, complete removal of all aromatic content in fuel is not immediately possible, as aromatics are needed to ensure planes function optimally.
“Aromatics are added to the fuel to keep the seals in the aircraft working. And when you remove them, then you get things happening like seals starting to leak, tanks leaking, the pumps becoming unreliable,” explained Ron van Manen, head of strategic development with the Clean Aviation Joint Undertaking, an EU and industry-backed programme to accelerate green aircraft innovation.
“There are a number of NGOs who are saying – and they have a very valid point – we can remove the aromatics from fossil fuel much sooner. The issue is, if you took them out tomorrow, the aircraft would have a problem.”
Adapting the current fleet to run without aromatics would require a costly retrofitting, which airlines are unlikely to adopt in the short term. Refuelling stations would also need to be upgraded to handle aromatic-free fuels.
“That timeline to modify the fleet to be able to fly on fuels without aromatics is probably about a decade unless you make it mandatory,” said van Manen.
This update will eventually become inevitable, however, as Sustainable Aviation Fuels (SAFs), such as second-generation biofuels and electro-fuels, are aromatic free. Under EU proposals, at least 63% of fuel uplifted by planes at EU airports will be SAFs by 2050.
Cuffe is not the only MEP to champion the inclusion of non-CO2 effects in the ReFuelEU Aviation proposal. Nicolás González Casares, a centre-left MEP directing the file in the European Parliament’s environment committee, has called for a European Commission report on “optimising the aromatic content of aviation fuel” to be prepared by 2030.
German MEP Jutta Paulus, a Green lawmaker in charge of preparing the European Parliament’s industry committee opinion on ReFuelEU Aviation, has also pushed for greatly reduced levels of aromatics and sulphur in kerosene.
Asking fuel suppliers to alter the composition of kerosene may push up prices, but the cost impact will be limited, according to Paulus.
“It’s not a technological problem, you can easily lower the sulphur and the aromatic content of fuels. It does cost money; you will have a 5% or 10% surcharge on aviation fuel. But it’s not tripling the price of the fuel,” Paulus told EURACTIV in a February interview.
It is expected that a reference to non-CO2 effects will be included in the Parliament’s amended ReFuelEU Aviation file, which is being shepherded by Søren Gade, a centrist lawmaker from Denmark.
The topic is likely to face greater opposition from EU member states, though it is not without advocates among the EU Council of Ministers – most prominently the Netherlands. In a document seen by EURACTIV, the Dutch government encouraged the French presidency of the Council to add a new clause obliging the European Commission to explore means to mitigate aviation’s non-CO2 climate impact, with the findings presented in a report by the end of 2023.
The increased focus on non-CO2 effects by lawmakers was welcomed by the clean mobility NGO Transport & Environment (T&E), which has strongly campaigned to get the issue on the legislative agenda.
“Now is our last chance to correct a major problem of the Fit for 55 package: the absence of aviation non-CO2 mitigation,” said Matteo Mirolo, aviation policy officer with T&E.
In addition to a reduction of the aromatic and sulphur content of jet fuel, T&E is calling for the establishment of a monitoring system to quantify non-CO2 effects under the EU’s carbon market.
“At a time when bold, ambitious climate action is needed, the EU cannot accept that two-thirds of aviation’s climate impact continues to fly under the legislative radar,” T&E wrote in a recent briefing on the subject.
Sean Goulding Carroll, EurActiv.com
Effect of fuels, aromatics and preparation methods on seal swell
Published online by Cambridge University Press: 12 April 2021
New alternative jet fuels have provided many advantages in the aviation industry, especially in terms of economics and environment. However, fuel–seal compatibility is one of the major issues that restricts alternative fuel advancement into the market. Thus, to help understand and solve the problem, this study examines the swelling effect of prepared and non-prepared O-rings in different fuels and aromatic species. Stress relaxation experiments were carried out to evaluate seal compatibility under compression, which mimics engine operation conditions. Seals were compressed and immersed in a variety of fuels and their blends for about 90h while maintaining a constant temperature 30°C and constant compression force of 25% seal thickness. The two types of elastomers investigated were fluorosilicone and nitrile O-rings, which are predominantly used in the aviation industry. Meanwhile, three different fuels and aromatic species were utilised as the variables in the experiments. The fuels used were Jet-A1, SPK and SHJFCS, while the aromatic species added were propyl benzene, tetralin and p-xylene. The swelling effects were determined from the P/Po value. Results indicate that Jet-A1 has the highest swelling effect, followed by SHJFCS and SPK. It was observed that the higher the percentage of aromatics in fuel, the higher the rate of swelling. Furthermore, prepared seals had a lower swelling rate than did non-prepared seals. Meanwhile, the intensity of the swelling effect in the Jet-A1-SHJFCS blends was in the order of 60/40, 85/15 and 50/50 blend. The work done in this study will aid in the selection of suitable aromatic species in future fuels. The novelty of this research lies in the determination of the appropriate amount of aromatic content as well as the selection of type of aromatic and its mixture fuel. Moreover, the various proportions of fuel blends with aromatic are investigated. The primary aim of this study is to understand the behaviour of prepared and non-prepared seals, and their compatibility with alternative fuels.
Graham et al.(Reference Graham, Rahmes, Kay, Belieres, Kinder, James, Millet, Ray and Vannice6) and other studies suggested the minimum aromatic content in a fuel is about 8% on average. This percentage is obtained from vigorous research, but it can go up and down in the future, depending on the types of fuels and aromatics used. It is considered as a safe minimum level of aromatics(Reference Hileman and Stratton1). Besides that, the aromatic content in kerosene ranges from 8% to 22%. In common jet engine fuel, the high aromatic content encourages the seals to swell, thus providing more protection from leakage. In the case of renewable fuel, the seals tend to extract since it contains no aromatics. These problems can be overcome by adding aromatics to the fuel or by blending it with conventional jet fuels.
The concentrations of aromatics must be minimised to reduce carbon emission(Reference Matthew, Edwin, Graham and Minus7). Another main purpose of alternative jet fuel production is to have low-sulphur fuels. In addition, it is important for the fuel to have good lubricity for the engine to run smoothly. Other than aromatics, synthetic jet fuel can also be blended with conventional jet fuel to gain the required properties of aviation fuel. The maximum aromatic content is regulated by environmental concerns since aromatics do not burn cleanly. On the other hand, the minimum content was set to improve lubricity and prevent leakage. This is because some chemical contents in conventional jet fuels provide a better swelling effect than that provided by the synthetic fuel–aromatic mixture(Reference Thomas, Fuller and Terauchi8). In this case, new jet fuels can be improved by eliminating or reducing the undesired properties of conventional jet fuels.