A study carried out by consultancy CE Delft and commissioned by green group Transport & Environment (T&E) suggests those living in proximity to busy airports are at risk of serious health conditions by exposure to ultrafine particles emitted from aircraft. It found nearly 52 million people, more than 10% of Europe’s total population, live within a 20km radius of the 32 busiest airports in Europe and are particularly exposed to ultrafine particles (UFPs). This can be linked to the development of respiratory problems, cardiovascular effects and pregnancy issues, says the study. As a result of extrapolating illnesses around Amsterdam Airport Schiphol to those 32 airports, the researchers estimate aviation UFP exposure may be associated with 280,000 cases of high blood pressure, 330,000 cases of diabetes and 18,000 cases of dementia. The amount of UFPs emitted from flights depends strongly on the composition of the jet fuel and the study estimates that the use of 100% hydrotreated jet fuel with very low sulphur and aromatics can reduce UFP emissions and health risks by up to 70%.

UFPs, which are less than 100 nanometres in diameter, or 1/1000^th the thickness of a human hair, are of particular concern because they penetrate deep into the human body and have been found in the blood, brain and placenta. Despite the growing evidence of the harmful long-term effects on health and mortality, T&E says the pollutant remains largely under researched and unregulated and the study provides a first estimate of the scale of the problem caused by aviation-related UFPs.

As well as at high altitudes, where climate-related effects such as warming contrails take place, UFPs from planes are also emitted on take-off and landing, meaning residents living near airports are particularly affected, and people living within a 5km radius can breathe in air that contains on average, anything from 3,000 to 10,000 UFPs per cubic centimetre emitted by aircraft.

As there is a correlation between people living near an airport and lower incomes, T&E argues the most vulnerable in society are the worst affected by air pollution. Although not covered by the study specifically, airport personnel working on the apron are some of the most exposed to these emissions, “constituting an unquantified but serious risk to their health,” warns the study.

“Can living near an airport make you ill? The tragic answer is yes,” said Carlos López de la Osa, Aviation Technical Manager at T&E. “Planes release tiny particles that may be linked to pulmonary and cardiovascular diseases. This hidden health crisis has been ignored by politicians who have prioritised the growth of the aviation sector and business travel over the health of its own people, often the poorest.”

T&E says there are a number of ways the problem can be tackled: reduce the amount of air traffic at airports and curb further expansion; move to cleaner burning fuels through hydrotreatment, a well-established process already used to remove sulphur from fuels for cars and ships; and use cleaner technologies like sustainable aviation fuels and zero-emission aircraft. It estimates hydrotreating fossil jet fuel, which adds hydrogen to the fuel, removing impurities and improving its composition/combustion properties, could cost less than five cents per litre. Hydrotreatment would have an additional benefit in contrail abatement.

“It’s not often that an alarming problem affecting millions of people can be reduced, and at a low cost,” said López de la Osa. “Dirty fumes caused by planes can be drastically reduced if we clean up the fuel. The road and shipping sectors took this necessary step years ago, but the aviation world has been dragging its feet.

“Reducing UFP emissions through better quality jet fuel would not only be beneficial for the population living near airports but also for the planet.”

Adds the study: “Although the costs of producing fuels with a low concentration of aromatics and sulphur would be higher than the cost of producing conventional jet fuels, the health and climate benefits outweigh these and other additional costs so that economic welfare would increase when these fuels would be used. Hence, there are good reasons to mandate or incentivise their use.”

T&E recommends that sampling points should be installed in and around EU airports to better quantify UFP concentration levels with a view of introducing target values for UFP concentrations in the next review of the Ambient Air Quality Directive. It also calls for an EU jet fuel standard to be created with a progressive reduction of aromatics and sulphur content “which will prepare the ecosystem for 0-aromatic, 0-sulphur SAF”.

Photo (Roger Cremers): Amsterdam Airport Schiphol

Christopher Surgenor

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New research commissioned by Royal Schiphol Group, which operates Amsterdam’s Schiphol Airport, has concluded it must cut carbon emissions by at least 30% below 2019 levels before 2030 – compared to the national ambition of 9% – to meet climate targets aligning with the Paris Agreement. The Group commissioned two studies, one by the Netherlands Aerospace Centre (NLR), the other by sustainability research body CE Delft, to help establish what actions would be needed to contain the airport’s CO2 emissions within Paris parameters. Options proposed for Schiphol, one of Europe’s biggest air hubs, included further development of new technology, rapid upscaling of sustainable aviation fuel and “ambitious” demand management focusing on long-haul flights, premium class travel and private flights. The research also concluded that a net zero target for a specific year was insufficient to achieve decarbonisation goals and highlighted the need for ongoing incremental improvements.

“Given the strong international nature of aviation, it is essential that the polluter pays,” commented Royal Schiphol Group on the conclusions of the studies. “A strengthened national and international policy is needed.”

Based on the two reports, the group has recommended a package of remedial initiatives headlined by replacement of the Dutch air passenger tax with a distance-based tax targeting long-haul flights, which produce aviation’s highest CO2 emissions, and taxes on business class and private flights, with all takings to be reinvested in the Dutch aviation sector to assist its transition from fossil fuels.

Royal Schiphol also called for a broadening of the EU Emissions Trading System to include intercontinental flights, which are currently exempt, along with a Carbon Border Adjustment Mechanism (CBAM) in Europe to prevent carbon leakage, and it endorsed a global kerosene tax and SAF blending obligations, to be overseen by ICAO.

The Schiphol recommendations follow a controversial decision last year in which the airport, mirroring the ambitions of its biggest shareholder, the Netherlands government, announced it would progressively cap the number of flights as a measure to reduce aircraft noise around the hub and beneath flight paths. KLM, the national and most affected airline, and IATA, on behalf of other operators, immediately launched court action to block the plan. They achieved temporary deferral of the ruling, a decision which was quickly overturned on appeal. But then the government suspended the plan, despite continued argument by the airport that flight restrictions would still be needed to contain noise and reduce emissions.

The report by the Netherlands Aerospace Centre estimates the nation’s aviation activity accounted for 1.16% of total global emissions from aviation, and that 96% of the Netherlands’ aviation CO2 was generated at Schiphol Airport.

“Current in-sector decarbonisation measures, excluding offsetting, are not enough to meet Intergovernmental Panel on Climate Change (IPCC) derived carbon budgets compatible with 1.5 degrees Celsius global warming for Amsterdam Airport Schiphol,” says the report. “Significant demand management measures, to be implemented by 2030 at the latest, seem the only viable way out.”

It says 80% of Dutch flights are intra-EU and contribute about 20% of total aviation CO2 emissions, whereas 15% of the longest distance flights (over 5,000 km) are responsible for some 75% of emissions. “As such, demand management measures targeting long distance flights are more effective than measures reducing total demand,” says NLR.

The level of CO2 emissions in 2030 is the key determinant for cumulative emissions over the 2020-2050 period, stresses the report. Cumulative emissions 2020 to 2030 are governed by fleet renewal, operational improvements, SAF blending and the traffic network (number of flights). Cumulative emissions 2031 to 2050 are governed by RefuelEU Aviation, annual efficiency improvement and the 2030 emissions level. Additional and higher quality SAF, or further efficiency improvements only make a limited 2-8% impact on cumulative CO2 for 2031-2050.

The CE Delft report for Schiphol estimates aviation’s 2019 proportion of global CO2 emissions was 2.4% from tank-to-wing emissions – those created purely from aviation fuel combustion – and 3.9% from well-to-wing emissions, which also incorporate the CO2 expelled from fuel production and distribution.

“In the last decades aviation emissions grew by 3-4% per year,” it reports. “Growth in flights has always outperformed the efficiency improvements by new aircraft types and more efficient operations, leading to growth in emissions.

“A net zero target in a specific year is not sufficient. Global warming is driven by the cumulative greenhouse gas emissions between today and the moment when global net zero is achieved. In-sector action between now and 2030 reduces cumulative CO2 emissions but overshoots the majority of airport carbon budgets.”

The report says replacing fossil fuels with SAF is technically relatively easy but expensive and predicts technological breakthroughs such as battery-electric or hydrogen propulsion would not lead to significant emission reductions in the next two decades. It adds new aircraft types currently in development will be in operation in 2050, powered by kerosene or SAF.

“Immediate scaling up of biofuel production and pre-commercial development of the synthetic fuel production are essential,” says CE Delft. However, it cautions that availability of biomass fuel feedstock and renewable energy would be limited in coming decades, and demand for these resources would be high among competing sectors and global regions.

“Technological breakthroughs will come too late and SAF production has limits,” warns CE Delft, adding: “The instruments that are currently in place are not sufficient. They need to be updated or replaced as soon as possible.”

The CE Delft report concurs with the NLR conclusion that demand management measures are necessary to align the aviation sector with the goals of the Paris Agreement.

However, CE Delft acknowledges that if the number of long distance flights from the Netherlands is reduced, a large number of passengers and cargo operators will switch to other airports, while others will fly less as a consequence of a decline in connectivity and higher ticket prices.

“If the ambition to reduce CO2 is much higher in the Netherlands than in neighbouring or competing countries worldwide, this may lead to competitive disadvantages in the short term,” it says. “Not taking this action will have tremendous consequences in the long term.

“The aviation industry worldwide has to answer the question as to how it prevents a substantial overshoot of the remaining carbon budget. Action is needed in all parts of the world. This includes the development of new technology, fast upscaling of sustainable fuels but also ambitious demand management.”

Photo © Amsterdam Airport Schiphol (Roger Cremers)

Tony Harrington

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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.

Under current jet fuel standards, the aromatic content is limited to a maximum of 25% by volume and a minimum of 8%. In 2011, a jet fuel study for Lufthansa analysed around 2,000 individual batches of jet fuel. About 75% of the batches had an aromatic content between 16% and 20%, with 15 batches analysed at lower than 8%. From analysis of literature and data supplied by a major fuel supplier, the CE Delft research found that a large share of jet fuel sold in Europe has an aromatic content of 15 to 20% by volume. Other data on batches of Jet A-1 produced in a number of European and North American refineries showed a variety between 8% and 25%, with an average of 18.7% aromatics. This is all within the allowed range as set by jet fuel standards, notes the CE Delft report.

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.

“Moreover, in practice, aircraft sometimes use fuels with an aromatic content of less than 8%, probably unknowingly,” it adds. “All in all, there is consensus on the requirement for an upper limit of aromatics but there is no consensus in the industry for the necessity of a minimum level aromatics in jet fuel. Other than on financial grounds, there are no clear reasons not to reduce the upper limit. Further research is needed to confirm or deny the role of the minimum content of aromatics for their lubrication purpose in aircraft.”

The CE Delft study carried out interviews with industry experts and parties involved in the production and supply chain of jet fuel. It found a gradual reduction in the upper limit would be a possible way to decrease the aromatic and naphthalene content in jet fuel, as some parties indicated the jet fuel market might experience difficulties if a strict or abrupt reduction of the upper limit was enforced. Because of the financial and time investment this would require by refineries, a reduction of aromatics content might lead to a higher cost of jet fuel, although, suggests the report, this increase could contribute to closing the gap in price difference between sustainable aviation fuel and conventional fossil jet fuel.

As they are conforming to jet fuel standards, from the refinery perspective, there is currently no incentive, financially or legally, to modify the production process to diminish the content of aromatics, sulphur and naphthalene in conventional jet fuel, it points out. 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.

Even if fuel suppliers charged airlines for the higher cost, airlines may choose to refuel at other airports in nearby markets. However, says the report: “If the EU were to put a lower maximum aromatics limit for all EU airports in a regulation, with a proper monitoring, reporting and verifying system, there would be little room to bypass the requirements.”

The study analysed how a new system could be set up to monitor aromatic and naphthalene concentrations in aviation fuels, which would allow for the assessment of the impacts of policies like ReFuelEU Aviation on contrail formation and also provide for better estimates of aviation non-CO2 impacts in general, so “filling the data gap that currently exists”.

Under ReFuelEU Aviation, the European Commission is proposing mandatory supply and use of sustainable aviation fuel. SAF could require new standards for aromatic and sulphur content, even if just to confirm the same standards that kerosene has today, suggests the report.

“Monitoring of aromatic and naphthalene content can be internalised with the reporting of SAF shares by the fuel suppliers,” it says. “This approach involves the lowest possible additional cost for the sector and for authorities to monitor, process data and verify. However, the exact design of such a monitoring and reporting system should follow policy or legal requirements for SAF or a lower aromatic content in jet fuel blends.”

The study also looked at how new aviation fuel specifications to reduce contrail formation could be drawn up in the EU and whether the jet fuel ASTM and DEF standards could be set under EU legislation. The report argues there is no EU or international law that would prevent the EU establishing a new standard for aviation fuel, implemented by either a new body or delegating it to an existing body like EASA, to reduce contrail formation and/or air pollution.

“ReFuelEU Aviation offers a great opportunity to establish a system for monitoring the aromatic content of jet fuel, which will increase our understanding of non-CO2 climate impacts and be a building block for addressing contrail formation,” the lead author of the CE Delft report, Jasper Faber, told GreenAir.

However, Adam Durant, CEO of Satavia, whose company is developing weather prediction and navigational avoidance technology designed to help aircraft operators avoid the risk of causing contrails in the first place, argues that while widely-available sustainable aviation fuels are definitely required to decarbonise aviation, the science linking exhaust emissions soot particles to contrail lifetime is still evolving.

“How long is it going to take to scale SAF production – 10, 20, 30 years, or even longer?” he questions. “Contrails management can be done at full scale within the next two years with adequate support. It is important to separate the two issues as SAF is not going to solve contrails.”

Photo: DLR