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Sustainable Aviation Fuels: Green but Remote Alternative

By Alicia Arizpe | Mon, 03/08/2021 - 10:58

Aviation has grown at a steady pace during the past decades and while the pandemic has put the sector in pause, experts at Morgan Stanley forecast a recovery by late 2023 or 2024. Despite the effects of COVID-19, IATA says by 2035 the aviation industry expects to transport 7.5 billion people. The sector’s rapid growth rate rose concerns about its growing carbon footprint. While the sector represents only 2.4 percent of all manmade carbon emissions, according to EESI, it is finding itself subject to increased pressure to become greener. Thus, the sector has implemented a number of measures aimed at keeping emissions down and decreasing them over time. Several governments across the globe have set sustainability goals aimed at reducing the environmental impact of aviation, while airlines have set the goal of halving their CO2 emissions by 2050.

Fluctuating oil prices are also motivating a decrease in the airline industry’s dependance on fossil fuels. These circumstances have led both airlines and planemakers to turn towards green jet fuels as a potential alternative to reduce the sector’s carbon footprint. However, while significant advances have been made, there is still a long way to go before the industry can fully rely on them.

Jet fuel and Its Alternatives

Jet fuel is a product of oil refinement similar to gasoline and diesel. While commercial aircraft use the same type of jet fuel called Jet A, a large number of alternatives are currently being explored to reduce oil dependance and carbon emissions. Researchers have explored alternative fuels including hydrogen, methanol, natural gas, methanol, ethanol and other substances, all of which present their own individual safety and infrastructure challenges, which would require a significant redesign of the aircraft. A different approach has been the generation of synthetic fuels derived from coal or natural gas but these often present higher CO2 emissions during their production.

To be classified as a sustainable aviation fuel (SAF), according to the IATA, a fuel must follow several criteria including reducing lifecycle carbon emissions and manufacturing from raw materials different from crude oil that can be obtained without depleting natural resources. SAFs can be generated from a variety of resources including algae, used cooking oils and other vegetable oils, sugar beets, sugarcane, straw, sawdust and other waste. These fuels must also share physical and chemical characteristics with regular jet fuel so it can be mixed with it in what is called a “drop-in” replacement. These characteristics include, but are not limited to combustion point, corrosion, fluidity, thermal stability and volatility. IATA explains that biofuels must meet the criteria for use by commercial aircraft to avoid the redesign of engines, fuel delivery systems or the airplane itself. The use of drop-in replacements also reduces the investment airports have to make to fuel arriving aircraft as it eliminates the need to develop parallel infrastructure for green and non-green fuels.

SAFs in Aviation

SAFs were used for the first time in 2008 in a Virgin Atlantic flight, according to Wired. During the following years, more and more airlines began blending them with regular jet fuel up to a 50 percent mix. In recent years, airlines are investing in the development and implementation of biofuels. “In 2019, KLM was the first airline in the world to sign a commitment for the development and purchase of SAF with SkyNRG,” said Maud Oostenbrink, Commercial Director Mexico at Air France-KLM, to MBN. Biofuels have already been used by Mexican airlines Aeroméxico and Interjet.

While these alternatives are more used in commercial flights, their use is far from widespread as they currently represent less than 1 percent of jet fuel demand. One key challenge toward wider implementation of SAFs in commercial flights is their cost, which can be up to three or four times that of regular jet fuel.

Mexican Biofuels

While cost might be an impediment, researchers, companies and industry bodies are actively looking for ways to improve SAFs. Mexico, for example, has made efforts in the development of biofuels and launched a SAF Initiative: “a public-private initiative, currently in process of legal formalization, that seeks to drive the integral development of the supply chain for sustainable aviation fuels in Mexico,” said Oostenbrink. This initiative, she explained, aims to gradually incorporate national and international airlines, industry associations and other players to “seek agreements with operators to include at least 2 percent of SAF in total jet fuel usage by 2024 and construct four bio-refineries near the airports of Mexico City, Guadalajara, Cancun and Monterrey.”

Mexico’s efforts to develop biofuels have also led to the creation of a Bio Jet Fuel Cluster (Cluster Bioturbosina). This cluster brings together national and multinational industry players such as Aeroméxico, Boeing and ENER with local research centers across the country to develop collaborative networks that facilitate the production of this fuels, among other sustainable energy initiatives. Research initiatives include the use of native plants such as Salicornia bigelovii, a plant that can be grown in marginal zones and does not compete with food-production plants, in the development of biofuels. Cluster members are also working on the development and improvement of bio jet fuel production methods, among other research projects that aim to eventually streamline the production of sustainable fuels.

However, local efforts to produce SAFs have seen several setbacks. Oostenbrink explained that the former efforts to speed up the local development of bio jet fuels were “to be funded by the Mexican government and the original agreement included government subsidies worth US$18 million, most of which was destined to SAFs. However, austerity policies of the new administration have put a hold on contributions.”

While the widespread implementation of SAF might be far in the future, it is not the only initiative implemented to reduce the aviation industry’s carbon footprint. Numerous technological advances have made improvements in engines and avionics to bring emissions down. For example, the retro-fitting of aircraft wings to introduce winglets has allowed the sector to reduce the emission of 80 million tons of CO2 since 2000, according to the Air Transport Action Group (ATAG).

Alicia Arizpe Alicia Arizpe Senior Writer