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Vegetable kerosene

Researchers from Unicamp develop high purity biofuel for airplanes

World aviation accounts for 2% of total carbon dioxide (CO2) emissions produced by man, according to the International Air Transport Association, comprised of 230 member airline companies from around the world. According to the association, 10% of the fuel to be used in 2017 is expected to be alternative fuel and will help reduce emissions. In 2010, the European Union will begin monitoring the airplanes that operate in Europe to mitigate this problem. This has resulted in a search for more suitable aircraft fuel. A biofuel produced at FEQ, the Chemical Engineering School at the State University of Campinas (Unicamp) is among the alternatives that may become a reality at airports. In the opinion of professor Rubens Maciel Filho, coordinator of the project, the new aircraft fuel option could be about 30% less expensive to produce and much less polluting than traditional aviation kerosene. The team of researchers has already filed a patent request with INPI, Brazil’s National Institute of Industrial Property, for the production and purification process of a biokerosene based on vegetable oils, the source of which the researchers chose not to disclose. The new fuel, because it comes from a renewable source, does not emit such pollutants as sulfur, nitrogen compounds, hydrocarbons or particle materials, as is the case of petroleum-based fuel, which contributes to the balance of emissions of carbon dioxide (CO2), the gas that is one of the leading causes of global warming. “This is 99.9% high purity biokerosene,” says Maciel, who is also one of the coordinators of FAPESP’s Bioen, the Bioenergy Research Program.

The researchers’ next steps in order to make progress in terms of consolidating the product include tests on airplane engines and production on a semi-industrial scale. To this end, Unicamp’s Inova innovation funding agency, co-holder of the patent, is interested in negotiating with companies to assign the right to exploit the new technology commercially. The related market is huge. According to IATA, the turnover in 2007 – the latest available data – totaled US$ 136 billion, or 28% of airline companies’ operating expenses.

The production process of vegetable oil biofuel is known and is similar to that of biodiesel, but it is more complicated. Both processes include a chemical reaction known as transesterification, in which vegetable oil, obtained from crushing the fruit of oleaginous plants, is refined. It then reacts with an alcohol and a catalyst (the substance that causes the chemical reaction), resulting in the fuel. The process for the production of biokerosene uses sugarcane ethanol as its reagent, also a renewable raw material. “In the case of biokerosene, the separation stage is much more elaborate in order to comply with aviation fuel characteristics and specifications, which are much stricter,” Maciel explains. His research work and patent filing included the collaboration of researchers Maria Regina Wolf Maciel, Cesar Benedito Batistella and Nívea de Lima da Silva, all from Unicamp. “Biokerosene has to be very pure, and free of the many compounds and impurities that can jeopardize the quality of the jet combustion system; in addition, it must have very specific viscosity, density and calorific power, which is not required from biodiesel.”

The transesterification takes place inside a reactor where the vegetable oil triglycerides react with the ethanol to form the ester – the chemical group which biokerosene belongs to – as well as glycerin, water, fatty oil molecules, gliceride, and the remaining non-reacted ethanol. One of the breakthroughs in this phase of the technology developed by the Unicamp team is in the field of reactions, which involves precisely balancing the several variables involved in the chemical reactions that result in biokerosene. The separation phase was decisive for the Unicamp team to develop its process. This phase involved isolating the biokerosene, the catalyst, water, and the impurities found in the reaction agent. And this is where innovation of the process developed by Maciel Filho’s team lies. He says that the isolation is conducted in an intensified separation process they developed, under temperature and pressure conditions that result in obtaining kerosene in an economically feasible manner. This process complies with the aviation kerosene criteria established by the National Petroleum Agency. This last point was confirmed by analyses conducted at Unicamp and at IPT, the Technological Research Institute.

The results of the analyses were compared with ANP’s aviation kerosene specifications table,” explains Maciel. The analyses showed that the biokerosene developed at Unicamp has similar characteristics to those found in traditional fuel because its freezing point is much lower than that of other products reported in literature. Biokerosene with no additives can also be used in blends with petroleum-extracted kerosene, thus significantly reducing the emission of sulfur, nitrogen compounds and particles and helping the CO2 balance. Although there are several research projects under way and biofuels are being tested elsewhere in the world, Maciel Filho emphasizes the importance of the level of purity of his team’s biokerosene. “Although the existence of experiments and tests using biokerosene is widely known, we did not identify any research work or patents on this topic in technical literature that reported obtaining high purity biokerosene,” he states.

Perhaps there is no other identical product, but some airline companies have already conducted experiments with airplanes flying on biofuels. An example is the United States’ Continental Airlines, the world’s fifth biggest airline company, which recently announced that it had conducted the first demonstration flight fueled by biofuel. The demonstration flight was held in Houston, Texas, USA, on January 7 of this year, using a Boeing 737-800, in which one of the engines was filled with traditional fuel and the other with a blend of kerosene and biofuel from algae and the Barbados or physic nut (Jatropha curcas). The flight lasted 90 minutes and the airplane was not modified in any way for testing purposes. During this flight, several successful maneuvers were performed, such as re-starting the engine, speeding up and slowing down. According to the company, the biofuel blend performed better than traditional fuel, with 1.1% higher efficiency during different stages of the flight. In addition, the level of greenhouse gases emitted during the test flight was down by 60% to 80% relative to the emissions of traditional fuel. “Biokerosene, like other biofuels from renewable sources, is environmentally sustainable, enhances our agribusiness, adds value to Brazilian products and reduces oil consumption, enabling one to use fossil fuel to make products that are more sophisticated than fuel in the fields of chemistry, plastics and fertilizers,” says Maciel.