Even as aircraft engine makers continue their very focused efforts to reduce fuel consumption and emissions, the use of biofuel alternatives to jet-A is an increasingly important facet of the campaign to make air transport more environmentally sustainable. Plans for making biofuels a more mainstream option for operators now account for around half of all the objectives set by the Advisory Council for Aviation Research and Innovation in Europe (Acare). The group, which is backed by the European Commission (EC) and industry players, is working toward the ambitious goals of reducing both carbon dioxide (CO2) and nitrogen oxide (NOx) by 75 percent, and noise by 90 percent.
In 2011, the EC launched its Aviation Biofuel Path 2020 program, which has the main objective of getting aviation biofuel production up to two million metric tons per year. This represents slightly less than four percent of current European consumption of jet-A.
Total is among the oil companies that has made a commitment to advancing this cause. “Biofuels, provided that they are produced in a sustainable way, are very relevant to improving the energy efficiency of air transport,” said the French group’s head of biotechnology Phlippe Marchand.
Two methods for producing synthetic fuels, Fisher-Tropsch and HEFA, are already certified. But in the case of Fisher-Tropsch, heavy investment is required with over $1.3 billion required to build a plant with the capacity to produce 80,000 metric tons of fuel annually.
The HEFA process is compromised on the question of sustainability since it relies on the availability of ingredients such as palm oil. In an attempt to get around this, Total has looked a fermenting sugars as an alternative, partnering with California-based Amyris to develop different sources of sugar, such as beets.
Total’s first extraction plant for processing sugar-based fuel is now operational in Brazil and the company is considering the possibility of establishing one in France. In June 2013, an Airbus A320 powered by CFM International CFM56 engines made an experimental flight with a fuel mix comprised 10 percent of a new fuel called farnesane. According to Marchand, the engines emitted around 80 percent less CO2 than if they had been run purely on jet-A. Another important plus is that these new fuels emit very little soot compared with the damaging particles that come from jet-A.
In May, an A330-200 operated by KLM Royal Dutch Airlines made a 10-hour flight from Amsterdam to Aruba with tanks filled with a 20 percent blend of fuel made from used cooking oil. In the same month, a two-year study commissioned by Airbus and partners, including Virgin Australia, reported that Australia’s mallee tree could be another sustainable raw material for biofuels.
Compatibility Is Paramount
Before widespread adoption of alternative fuels can be accepted, aircraft and engine manufacturers will have to be satisfied on certain key technical requirements, namely the density, viscosity and compatibility of the new fuels with all the internal parts of the engines. “These are the topics we are working on as manufacturers,” said Frédéric Eychenne with Airbus’s new energy project office.
Both Airbus and Boeing have conducted numerous flight tests in recent years with several types of biofuels. As part of this process, Boeing has increased tests on military aircraft using various combinations of jet-A and synthetic fuels made through the Fisher-Tropsch method. In January 2014, it tested a fuel produced from Jetropha, a plant that can be grown in arid climates and which emits about half the CO2 emissions of an equivalent volume of jet-A. Boeing also has biofuel alliances with Etihad Airways, Abu Dhabi’s Masdar Institute and Total.
Nonetheless, there appears to be consensus among the leading stakeholders that the widespread acceptance of these new fuels will take some time. “For the next 30 to 40 years, kerosene [jet-A] will remain the main aviation fuel,” predicted Eychenne.
Over and above the complex technical requirements, the new fuels will need to be available worldwide at reasonable prices if they are to be accepted by aircraft operators. Contrary to perception, the price of jet-A has remained relatively stable over the past three or four years. By contrast, the ingredients used for biofuels are subject to significant volatility in pricing, partly because they are also in demand by the food industry. Some alternative sources of fuel, such as those produced from microalgae, are not yet mature processes. Eventually, Total believes that this pricing imbalance between oil and fuel sources such as sugars will be corrected.
Part of the solution may come from the sea. The U.S. Navy has managed to produce a synthetic jet fuel from seawater from which CO2 and hydrogen are captured through a process of electrolysis. Initial estimates suggest that the fuel produced might be priced somewhere between $3 and $6 per gallon, compared with less than $3 for jet-A.
Jet Fuel’s Environmental Impact by the Numbers
· Currently consumes around 200 million metric tons of fuel per year.
· Represents about 3 percent of global CO2 emissions.
· If nothing is done, given the projected growth in global air traffic, total emissions from air transport could be six times higher by 2050.
Source: European Commission, “Aviation Biofuel Path 2020”
Three Alternative Fuel Processes
· The Fisher-Tropsch method was certified for aviation in 2009 and involves liquefying biomass, gas or coal. Invented as far back as 1923, the process is capital intensive.
· HEFA was certified for aviation in 2011. It involves fuel being made from substances such as palm oil and microalgae. Disadvantages include the fact that it competes with food for available land and is also subject to low yield rates.
· A process of fermenting enzymes is used to convert sugar cane or beet pulp into the new fuel called farnesane.