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The potential to power planes with clean synthetic fuels

Reducing emissions from the ever growing aviation sector is no easy task. Renewables-based synthetic kerosene production is one solution currently being explored

One of the bigger elephants blocking progress in the energy transition room is aviation. Alternatives to fossil-fuel kerosene are often as polluting as the conventional product and more expensive to produce. But few people are willing to stop flying. Renewables-based power-to-liquids projects for kerosene production may help ease the aviation elephant out of the door

Direct emissions from aviation account for more than 2% of global emissions. If global aviation was a country, it would rank in the top ten emitters, says the European Commission, the EU executive body. Someone flying from London to New York and back generates roughly the same level of emissions as the average person in the EU does by heating their home for a whole year, it estimates. Aviation’s climate impact will consume up to 22% of our remaining carbon budget until 2050, warns Stay Grounded, an international network aiming to tackle root causes of aviation growth and climate change. Not only does the aviation elephant appear firmly jammed in the room, it is also getting bigger. Consumption of kerosene will amount to around 94 billion gallons (roughly 306 million tonnes) in 2018, up over 4% from 90 billion gallons in 2017, compared to 81 billion gallons in 2015 and 70 billion gallons in 2010, says the International Air Transport Association (IATA), whose member airlines cover some 85% of all global commercial flight operations. In parallel, aviation’s carbon dioxide (CO2) emissions will reach around 897 million tonnes in 2018, up from 859 million tonnes in 2017, compared to 770 million tonnes in 2015 and 664 million tonnes in 2010, says IATA. Although the association says its target, set in 2008, of 1.5% annual average fuel efficiency improvement to 2020 is on track, air travel is expected to grow by an average 3.6% per year which is more than double the annual fuel efficiency improvement. Some 7.8 billion passengers will be travelling the skies each year in 2036, compared with around 4 billion in 2017. The best climate outlook IATA can muster is for net CO2 emissions from aviation to be stabilised at 2020 levels. Beyond that, all aviation growth is to be made carbon-neutral, for instance with carbon offsetting measures, which allow a particular industry to carry on polluting, but to offset its emissions elsewhere.

Sustainable aviation fuels

A whole new CO2 offset system has been devised to begin in 2021. Dubbed CORSIA, the Carbon Offsetting and Reduction Scheme for International Aviation will monitor, report and offset any annual CO2 emissions from international civil aviation that are above 2020 levels. Participation will be voluntary during the pilot phase 2021-2026 and will become mandatory for all states in the second phase, as of 2027. Nearly 70 states, including all EU member states, intend to participate, which together account for more than 86% of global aviation activity. Offsetting is not avoidance, however, and IATAs long term aim is to reduce net CO2 emissions by 50% to 2050 compared to the 650 million tonnes released in 2005. By mid-century, the aviation sector still expects to be releasing 325 million tonnes of CO2 into the atmosphere each year. Yet, it would seem that more could be done. IATA says sustainable aviation fuels (SAFs) from sustainable oil crops such as jatropha and camelina, from algae or from wood and waste biomass have the potential to cut CO2 emissions by up to 80% by this date. But blames quality rules for the fact this reduction is unlikely to be met in reality. The reason we can’t go beyond a commitment to reduce emissions more than 50% by 2050 compared to 2005 is that you would need 100% use of SAFs by then. Under current technical standards the highest blend permitted is 50%,” explains IATAs Chris Goater. The main institutions worldwide setting technical standards and certifying aviation fuel quality are ASTM International, a US-based standards organisation, and the UK government’s Ministry of Defence. Hitting this target also poses supply issues. SAFs are being produced and used in commercial flights every day, says IATA. But current volumes produced are still less than 1% of total jet fuel demand. And there is the problem of cost. Currently available commercial biofuels have a cost factor two to five times higher than conventional kerosene. Biofuels are not yet competitive, there is no technology that seems to be leading the field and no commercial airline that is taking the lead,” says Markus Köhler from DLR, a German aerospace research institute.

Renewables power-to-liquid

The fossil fuel industry has already enjoyed almost a century’s head start over SAFs, which are still in the early stages of commercialisation, explains Finnish oil company Neste, which produces both types of fuel. Fossil kerosene can be produced cost efficiently having achieved massive economies of scale, says the company. Overall world production in 2017 was some 96 billion gallons compared with a mere 6.6 million gallons of SAFs produced on a commercial scale. Ironically, Neste seems to be doing better producing the more expensive biofuels than conventional oil products. In 2017, Neste‘s operating margin in its smaller renewables sector with output capacity of 2.6 million tonnes per year was nearly double that in the conventional oil sector with production capacity of 15 million tonnes per year. Cynics could conclude that the mass production of SAFs could mean sinking profit margins, reducing the industry‘s enthusiasm for swiftly expanding output of alternatives to kerosene. To shift the balance, coordinated support including effective policy frameworks’” are needed, says IATA. Others agree and have tried to set the ball rolling. In August 2017, the International Civil Aviation Organization (ICAO), a UN agency, proposed a plan to increase biofuels use for SAFs to 128 million tonnes per year by 2040 and 285 million tonnes, or 50% of expected aviation fuel use, by 2050. Currently, 82 million tonnes of biofuels are used per year in all types of transport worldwide. But environment groups and other non-government organisations have strongly opposed the proposal because of the emphasis on biofuel feedstock for SAFs and the impact this could have on local farmers and indigenous people, food prices, deforestation and destruction of other biodiverse ecosystems. Studies show that increases in vegetable oils, sugar cane and cereals for fuel can also increase the use of synthetic fertilisers and pesticides, polluting water ways, and question the overall climate impacts of these fuels. NGOs such as the Brussels-based NGO Transport & Environment state that most biofuels are worse for the climate than jet fuel”. An approach that could help break the deadlock is dubbed renewables power-to-liquid“ and has the added potential advantage of improvements in fuel quality. IATA says it has supported different research projects on this topic and continues to actively monitor developments in this area. Based on our assessment, the technology still has some challenges to overcome to become commercial at scale,” says Goater. That said, it is a concept we like and will continue to support within our means to see this progress.” He says IATA is feedstock and technology agnostic” and that the association hopes a large number of production pathways and a very wide array of feedstock become commercially viable on a large scale because the industry needs every drop we can get”.

German demonstration plant

The interdisciplinary Advanced Energy Systems Institute (AES) at Germany‘s Bremen University is one organisation working to get electricity-based, green kerosene a step closer to market launch. If electricity from renewable energy sources is used and the carbon dioxide required obtained from the atmosphere, a closed CO2 cycle can be brought about, AES says. Just water and carbon dioxide are required for production, being converted into liquid hydrocarbons using electricity. The German government is supporting the three year KEROSyN100” project with over €4 million as part of a funding initiative titled Energy transition in the transport sector: sector coupling through the use of electricity-based fuels”. The basic engineering is being developed for a customised demonstration plant at the Heide refinery in northern Germany. Owned by the Klesch group, a Swiss-based industrial commodities company, the refinery processes up to 4.5 million tonnes of crude oil per year. Unlike the oil majors, the company does not have its own crude oil sources, potentially increasing its interest in non-crude oil feedstocks. Electricity to power the new process will be sourced partly from wind turbines whose production often has to be reduced because of electricity transmission grid bottlenecks and a lack of flexibility in the electricity transmission system. In principle, it will be possible to produce 100% synthetic kerosene by 2050, but international kerosene standards would have to be changed,” says Norbert Weber, spokesman for the refinery. The aim is to achieve a 50-50 fossil/synthetic share by this date. After completion of the project in 2021, a production plant could then be built by 2025, but whether it will be economically viable is not yet foreseeable”. But even with these unknowns, it is worth a shot given the alternatives. The biofuel route to SAFs needs huge areas and a lot of water, which in the current world and times of ever scarcer resources is not particularly sustainable,” says Weber. The electricity-based synthetic fuel route needs significantly less area and water.” Some experts also believe that such fuels could signify not only better sustainability but also a significant leap in fuel quality. Kerosene is a broad mix of various molecules, more of a chemical soup than a single, defined chemical species,” says DLRs Köhler. Indeed, the UK Ministry of Defence’s standard for aviation turbine fuel describes kerosene as a complex mixture of hydrocarbons that varies depending on the crude oil source and manufacturing process. Consequently, it is impossible to define its exact composition,” says Köhler. His colleague Patrick Le Clercq, adds: The advantage of producing synthetic kerosene, especially from non-fossil feedstocks rather than refining crude oil, is that kerosene’s chemical composition can then be more precisely designed, allowing improvements in the fuel‘s performance and emissions.”

Writer: Sara Knight