The aviation industry is committed to preserving the environment and is constantly looking at sustainable alternatives in an aircraft, be it engines, aircraft materials or alternative fuels. Aircraft and engine manufacturers, regulatory bodies and various aviation associations are all committed to working towards sustainable goals, even though air transport produces only around two per cent of global CO₂ emissions.

The International Air Transport Association (IATA) has recognised the need to address the global challenge of climate change and has adopted a set of ambitious targets to mitigate CO₂ emissions from air transport. The targets set are average improvement in fuel efficiency of 1.5 per cent per year from 2009 to 2020, a cap on net aviation CO₂ emissions from 2020 (carbon- neutral growth) and reduction in net aviation CO₂ emissions of 50 per cent by 2050, relative to 2005 levels.

Key Elements

And working in this direction, the industry has found that bio-jet fuels as one of the key elements in achieving these goals as they are the only low-carbon fuels available for aviation in the short- to medium-term. The aviation industry is interested in developing fuels that can be mass produced at a low cost and high yield with minimal environmental impact. These biofuels should be produced from crops that are fast growing plants which do not take up productive arable land, do not require excessive farming techniques or threaten biodiversity, provide socio-economic value to local communities and most importantly, result in a lower carbon footprint.

Biofuels derived from sustainable oil crops such as jatropha, camelina and algae, or from wood and waste biomass, can reduce the overall carbon footprint by around 80 per cent over their full life-cycle. Test flights using biofuels have been carried out by dozens of airlines and have proved that biofuels work and can be mixed with existing jet fuel. The airline industry has played an instrumental role in advancing technical certification for biofuels which can now be used on passenger flights. The first commercial flights using biofuels were successfully completed in 2011.

Second Generation Fuels

Theoretically, biofuels can be produced from any renewable biological carbon material although the most common sources are plants that absorb carbon dioxide and use sunlight to grow. Globally, biofuels are most commonly used for transport, heating, power generation from stationary engines and for cooking. The two most common feedstock sources for making biofuels are plants rich in sugars and bio-derived oils. Crops that are rich in sugars such as sugarcane or in starch such as corn, can be processed to release their sugar content. This is fermented to make ethanol which can be used directly as a petroleum substitute or additive. These fuels, knownas first-generation biofuels, are typically not suitable for use in aircraft as they do not have the necessary performance and safetyattributes for use on modern jet engines. However, bio-derived oil, commonly sourced from plants such as corn, soybeans, algae, jatropha, halophytes and camelina, is processed and can either be burned directly or converted by chemical processes to make highquality jet and diesel fuels. These are known as second-generation biofuels and can be used for aviation.

Sustainable biofuels could be an attractive alternative as their production is not limited to locations where fossil fuels can be drilled, enabling a more diverse geographic supply. In theory, biofuel feedstock can be grown in many places around the world, where the aviation industry needs it. And while, as for petroleum, there will be major producers of biofuel feedstock and it will likely be transported to where it can best be used, it is also likely that local smaller scale supply chains will be established.

The aviation industry is, therefore, looking at second or nextgeneration, bio-fuels that are also sustainable. This new generation of bio-fuels is derived from non-food crop sources. Secondgeneration bio-fuels can also be mass grown in a range of locations, including deserts and salt water. Each of the second-generation feedstock being investigated for aviation use has the potential to deliver large quantities of greener and potentially cheaper fuel.

It is unlikely, however, that the aviation industry will rely on just one type of feedstock. Some feedstocks are better suited to some climates and locations than others and so, the most appropriate crop will be grown in the most suitable location. It is likely that aircraft will be powered by blends of bio-fuel from different types of feedstocks along with jet fuel.

Jatropha Plant

Potential second-generation biofuel feedstock Jatropha is a plant that produces seeds containing inedible lipid oil that can be used to produce fuel. Each seed produces 30 to 40 per cent of its mass in oil. Jatropha can be grown in a range of difficult soil conditions including arid and otherwise non-arable areas, leaving prime land available for food crops. The seeds are toxic to both humans and animals and are therefore not a food source. Camelina is primarily an energy crop, with high lipid oil content. The primary market for camelina oil is as a feedstock to produce renewable fuels. The leftover ‘waste’ from the oil extraction can also be used as feed for chickens in small proportions. Camelina is often grown as a rotational crop with wheat and other cereal crops when the land would otherwise be left fallow as part of the normal crop rotation programme.

Algae Promising Feedstock

Algae are potentially the most promising feedstock for producing large quantities of sustainable aviation biofuel. These microscopic plants can be grown in polluted or salt water, deserts and other inhospitable places. They thrive off carbon dioxide, which makes them ideal for carbon capture from sources like power plants. One of the biggest advantages of algae for oil production is the speed at which the feedstock can grow. It has been estimated that algae produces up to 15 times more oil per square kilometre than other biofuel crops. Another advantage of algae is that it can be grown on marginal lands that aren’t used for growing food, such as on the edges of deserts. Halophytes are salt marsh grasses and other saline habitat species that can grow either in saltwater or in areas affected by sea spray where plants would not normally be able to grow.

Next Steps

With all these developments, the industry is getting ready to take the next step in the journey of alternative aviation fuels, i.e. ramping up to get enough of this low-carbon energy into fuel supply. The aviation industry has embraced the concept of biofuels with enthusiasm and has already completed much of the technical work needed to start commercial flights. Rigorous testing, both on the ground and in the air, has shown that biofuels can deliver equal and sometimes better performance than the current fuel. The biggest challenge now lies in ensuring a steady, reliable, cost-effective and sustainable supply of this new energy source. That means substantial investments have to be made in R&D and developing biofuels which in the long term will prove highly beneficial to society.

Airbus — A Catalyst

Airbus is a catalyst in the search for sustainable aviation fuels through a global programme connecting raw material producers, refiners and airlines to form regional ‘value chains’ on every continent. An industry-wide initiative to speed up aviation sustainable aviation fuel commercialisation in Europe has been launched by Airbus, the European Commission, leading European airlines and key European sustainable aviation fuel producers. This initiative, called the “European Advanced Biofuels Flightpath,” is committed to supporting and promoting the production, storage and distribution of sustainably produced drop-in sustainable aviation fuels for aviation use, with the objective to reach two million tonnes of production and consumption by 2020.

Boeing is the industry leader in global efforts to develop and commercialise sustainable aviation biofuel

Airbus’ launch of a sustainable aviation fuels roadmap has led to collaborative projects and flights with airline partners, along with approval of 50 per cent blends of Biomass to Liquid (BTL) and Hydroprocessed Esters and Fatty Acids (HEFA) fuels on commercial flights. Through May 2014, more than 1,500 commercial flights have been flown with alternative fuels worldwide. Airbus also is working with the European Commission and other stakeholders to develop a European roadmap for the implementation of sustainable aviation fuels in the “European Advanced Biofuels Flightpath” initiative.

In Canada, Airbus announced a partnership in 2013 with Air Canada and BioFuelNet Canada to evaluate solutions for production of sustainable jet fuel in the country. With adequate supply sources that have the ability to produce commercial quantities of sustainable aviation fuel and support from governments, Airbus believes that up to a third of aviation fuel could come from alternative sources by 2030.

Boeing Biofuel Projects

Boeing is the industry leader in global efforts to develop and commercialise sustainable aviation biofuel. A new sustainable jet fuel is essential to reduce commercial aviation’s carbon emissions, reduce industry’s reliance on fossil fuel and reach industry’s goal of carbon- neutral growth from 2020. Boeing is focused on so-called ‘drop-in’ sustainable biofuel which can be blended directly with the traditional petroleum jet fuel supply with no changes to airplanes, engines or fuelling infrastructure. Boeing’s goal is that by 2016, sustainable biofuel will address one per cent of global jet fuel demand, equivalent to 600 million gallons (2,271.25 million litres) of jet fuel. One per cent often represents the tipping point to show proof of concept for a new technology, leading to increased investment and more rapid market expansion.

Boeing is focused on alternative fuel development that meets sustainability criteria. This includes working with feedstocks that do not adversely affect local food supplies, freshwater supplies or land use policies. Many Boeing biofuel projects also encourage social and economic development such as new opportunities for farmers to use marginal land for sustainable aviation biofuel crop production. Boeing currently has active bio-fuel development projects on six continents, including in the United States, Europe, China, Japan, Middle East, Southeast Asia, Brazil, Southern Africa and Australia.