How algae could make aeroplanes fly

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Plane in middair

Every year, aeroplanes consume 1.7 billion litres of kerosene to fly goods and passengers around the world. The numbers of passengers and transported goods are rising all the time. Admittedly, fuel consumption and emissions have not risen any further in recent years thanks to more efficient aircraft engines. However, kerosene is made from petroleum. And because petroleum reserves are declining, this fuel will simply become too expensive for airlines one day. Even today, this fossil fuel accounts for a third of their operating costs.

The biggest algae experiment in Germany

It is now hoped that algae will solve the problem. Four years ago, researchers at Forschungszentrum Jülich (FZJ) in the extreme west of Germany began cultivating algae. Freshwater algae of the chlorella genus are now growing on an area of 1,500 square metres: in plastic tubes, in large hanging plastic bags and in stacked nets. These are all growing methods that take up little space and do not require any fertile agricultural soil.

Tiny plants with a big impact

The maximum size that microalgae grow is as thick as a human hair. That is an advantage, as their surface area is comparatively large. This means they can make optimum use of light when they convert light energy into chemical energy, much like photosynthesis in land-based plants. “The microalgae enrich oils in their cells. When they are grown under optimal conditions, we can achieve up to 23 percent in the greenhouse and 35 percent in the lab”, says Dr Dominik Behrendt, who works at the Institute of Bio- and Geosciences at the FZJ. To achieve these figures, the plant researchers withhold nutrients from the algae at a specific point in time. This provokes a stress reaction, which prompts the algae to produce more fats. The crude oil yield from algae is therefore many times higher than from other energy crops such as rapeseed or corn.

Extracting oil from algae biomass

Cultivating the algae is one thing. But techniques are also being developed in Germany’s largest algae experiment to extract oil from the harvested algae biomass. “We produce crude oil from algae by adding solvents to the algae, such as alcohol or acetone and hexane”, says Behrendt. The technique was developed by engineers at Brandenburg University of Technology in collaboration with the research department of the company Verfahrenstechnik Schwedt. They are just two of the twelve research institutions, universities and companies that are involved in the AUFWIND project in all. The Federal Ministry of Food and Agriculture (BMEL) has funded the project to the tune of 6.3 million euros.

Using waste gases as food

Commercial production is still a long way off. As yet, the production process is too expensive and the level of energy consumption far too high to compete with kerosene. Algae-based fuel and its production process need to be one thing above all, however: sustainable. This is why the researchers at the FZJ are already feeding their algae with CO2. The carbon dioxide comes from a nearby lignite-fired power station: the gas is separated off and liquefied, rather than being released into the atmosphere together with other waste gases.

Food from algae?

Over the next few years, the scientists want to improve the way the microalgae are cultivated, experiment with new species of algae and further develop their harvesting and extraction methods. Because the freshwater algae chlorella is already approved for human consumption, they will also explore how valuable proteins and other nutrients contained in the algae can be used in food production. Algae still have something of an image problem with many people – and pictures of green shimmering lakes certainly do not help. However, this could soon change in view of the many benefits that algae offer.