Responsible for approx. 2-3% of the world's greenhouse gas (GHG) emissions, it is understandably the subject of substantial criticism. Yet aviation is also one of the most difficult-to-decarbonise industries, and sustainable solutions are limited. These span sustainable aviation fuel (SAF) supplies; more efficient wide-body aircraft for long-haul routes; deploying either hydrogen, electric or hybrid aircraft for short-haul routes; and improving operations both on the ground and in airspace. What does this mean for net zero targets given the ongoing increase in air travel demand? According to the World Economic Forum, by mid-century the aviation sector's GHG emissions could increase upwards of 300% compared to 2005 levels “if no drastic measures are taken to reduce them". Given the industry's responsibility for such a large share of global emissions, the consequences of the sector failing to deliver on climate action would be significant.
Aviation numbers among the seven sectors that form part of the “Mission Possible" partnership between the “We mean business coalition", the Energy Transitions Commission, the RMI and the World Economic Forum. The energy intensity of the industry, in combination with the limited decarbonisation levers available, mean that the whole sector will need to transform if it is to meet net zero.
This is why the majority of the aviation players are working hard, despite ongoing post-pandemic recovery, to focus on sustainable growth and achieving industry targets: to reduce emissions by 50% by 2050 compared to the reference year 2005 and to become net zero by 2050 (set at the 77th IATA Annual General Meeting). The sector is constantly appraising innovative solutions and supporting the development of new technologies, which includes sustainable aviation fuel (SAF). This blog reviews the benefits and limitations of the new fuel in answer to the question of whether SAF can secure a green future for the aviation industry.
What exactly is SAF?
Paraffin is currently the main component in aircraft engine fuel. SAF is a drop-in fuel that can be used as a direct substitute for paraffin without requiring any changes to the engine, aircraft structure or airport infrastructure. In practice, there are two types of SAF: biofuels and e-fuels.
Aviation biofuel, also known as BAF (bio-aviation fuel), is a fuel produced from biomass, such as vegetable oils (e.g. palm oil or soybean oil), animal fats, sugar, starch, and certain algae. A study by the European Parliament estimates that 80% of SAF needs in the near future could be met by biofuel, produced from vegetable oils, used cooking oils, tallow, etc using HEFA (Hydroprocessed Esters and Fatty Acids) technology .
E-fuel is generated by extracting hydrogen from water with low-carbon electricity and then combining the hydrogen with CO2 and converting it into a liquid energy carrier. In Norway, a production facility called Norsk e-fuel is under development which will this year produce aviation fuel from renewable electricity, water and CO2. The plant is expected to supply 100 million litres of fuel per year from 2029.
Yet not all SAFs are equal when it comes to their associated GHG emissions. Production methods differ, and one study estimates that the biofuel made from palm oil produced in Indonesia would have 24 times the impact of SAF produced from grass in the United States, due to the deforestation associated with palm cultivation.
Can SAF replace fossil fuels?
SAF has several advantages:
- SAF is “drop-in" fuel, compatible with current engines (which is not the case with hydrogen, for example) which can be blended with up to 50% conventional jet fuel (for commercial aviation).
- SAF can be renewable when made from renewable electricity and water, or waste-derived when made from biomass.
- SAF emits significantly less GHGs over its life cycles than paraffin. Depending on the type of SAF, GHG emissions can be reduced by 15% to 80%. In addition to this reduction, SAF has a lower sulphur content (SOx) and emits less particulate matter (PM) which is important for aviation's impact on local air quality.
The technologies behind SAF are no longer new, and are beginning to be implemented more widely in the aviation industry. Already, more than 450,000 flights have been made using aircraft powered by this type of fuel. As of 2021, more than 100 million litres of SAF had been produced.
Despite these developments, the amount of SAF being used is, at present, still marginal. Of the 360 billion litres of fuel used by the aviation industry in 2019, less than 0.1% was SAF. But several countries wishing to accelerate the transition of the aviation sector have committed to go further. One striking example is France: as of 1st January 2022, 1% of all refuelling carried out in France must consist of SAF, with the amount rising to 2% by 2025 and 5% by 2030. The European Parliament has also recently adopted a bill requiring the integration of 37% sustainable fuels (including SAF but also electric and hydrogen aircraft) for EU airlines and airports by 2030 and 85% by 2050.
What are the limitations of using these new fuels?
The big challenge with SAF is producing these fuels in large quantities and at an affordable price: the current costs of SAF are 3 to 10 times higher than those of paraffin. In the drive to develop more sustainable solutions, some players in the sector are already requesting financial support from governments.
Beyond the issue of cost, the biggest limitation is the space and resource consumption required to produce these new fuels. Indeed, some biofuels are in direct competition with food crops. A study by the World Resources Institute estimates that the development of plant-based biofuel production would not be compatible with the food production needs of the human population by 2050. The study concludes that "the quest for bioenergy on a significant scale is both unrealistic and unsustainable." For this reason, it is possible that waste-based biofuels will be favoured in the future.
For e-fuels, the problem of large-scale production is the same: all the world's renewable electricity would not be sufficient to produce the amount of fuel used by aviation today. The Norsk e-fuel plant mentioned above could eventually produce 100 million litres of fuel per year, but it would take dozens of similar plants to supply Charles de Gaulle airport in Paris alone. And this only captures the energy demand of the aviation sector, not to mention the needs of the transport sector in general.
Finally, because of SAF's high development and operating costs, it is not clear whether the investments required to deploy these solutions on a large scale would be profitable. The passenger also faces a significant increase in cost from the use of even just a small proportion of SAF in the aircraft's tank.
And lastly, let's not forget that the climate impact of the sector is not limited to its paraffin consumption. The manufacture of aircraft and airport infrastructure has a significant impact on local air quality and noise pollution, as do the non-CO2 impacts of the contrails. Overall, there is more to be done than just waiting for SAF to become broadly available.
The way forward
The "Flying in 2050" report produced by The Shift Project and the Aéro Décarbo association concludes that even if technological progress does have a significant positive impact on the decarbonisation of the aviation sector, it will still be necessary to take sobering measures such as: making cabins denser, eliminating air travel when a rail alternative exists, improving public transport and intermodality, regulating private aviation traffic, reducing single-use plastic consumption, being more considerate about food and overall waste, abolishing the "frequent flyer miles" systems or allowing for earned airmiles to be used towards SAF.
What's more, meeting net zero targets will need to go beyond the responsibility of airlines alone. As discussed, the ongoing development of SAF fuels is promising for the transition within the aviation sector, but this must be accompanied by behavioural change. Travellers need to be prepared to pay more for their flights if they wish to fly on SAF, and both individual travellers and their employers will need to prioritise emissions-saving measures such as replacing short-haul flights with train journeys and business travel with videoconferencing.
Many companies already analyse their corporate travel emissions (Scope 3), and split them according to mode of transport. It can be a real eye-opener to learn that one business-class return journey from London to New York can emit as much carbon as a world average person's activities in a whole year – this all stacks up in the running total of a company's overall carbon footprint, and it's a footprint which companies are increasingly being held accountable for. It may represent something of a paradox, but if the aviation industry is to meet its targets and deliver on climate action, the sector should focus on getting customers to rethink how they relate to air travel, which mainly means: flying less.
Here are just a few examples of what that can look like:
- Passengers should be encouraged to fly directly rather than indirectly, since the biggest fuel burn rate happens during the take-off and landing.
- Public transportation at the final destination needs to be enabled, so that passengers don't rely on taxis and private cars.
- The environmental advantages of flying economy class need to be promoted. As much as we all love a bit of luxury, especially when on a longer flight, everyone should be made aware that a long-haul business and first class travel can be three to four times more carbon-intensive than economy class.
- Travellers should be offered the option of compensating for their emissions, whether via voluntary carbon compensation schemes or including compensation transparently in the air fare. It really costs a fraction of a ticket price to contribute to global climate action with high-quality carbon credits.
- AND… last but not least: light travel should be promoted, too. Pack less, pollute less: the heavier the load, the more fuel we need.
The conclusion? While SAF is a remarkable technology and has great potential to help the aviation sector meet its emission reduction targets, if companies want to meet their net zero targets, one of the best ways may be to review their business travel policy by redefining their priorities and favouring rail travel where possible. Our resources are limited and it takes a global effort on an individual level to implement smart travel.
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