How plants could soon be keeping our planes in the air

Our appetite for hopping on a plane and travelling thousands of miles has a footprint. The Air Transport Action Group (ATAG) says that in 2015, flights produced 770 million tonnes of CO2, with 12 percent of CO2 emissions from transport sources down to aviation.

It is against this backdrop that technology and innovation are changing the way we think about air travel and how our planes can be fuelled.

The solar powered aircraft Solar Impulse 2, for example, is in the final stages of its round-the-world solar-powered flight, while European airline Easyjet unveiled its concept for a zero-emission hydrogen fuel system this year.

In Germany, researchers are looking at nature – chiefly the idea behind photosynthesis – as a means of keeping planes up in the air.

Bauhaus Luftfahrt have been looking into what they call "new thermo-chemical reaction pathways" to produce synthetic kerosene from CO2 and water by using solar energy.

"This process is already happening in photosynthesis – in the natural photosynthesis process – where water and CO2 is combined with the energy of sunlight to make chemical energy," Andreas Sizmann, head of future technologies and ecology of aviation at Bauhaus Luftfahrt, told CNBC's Sustainable Energy.

"We realized that this process can be done without photosynthesis by reenergizing water and CO2 at high temperature in (a) reactor… to reverse the combustion process," he added.

Sizmann went on to explain how a reactant releases oxygen, which is then brought into contact with water and CO2, where the oxygen is "reclaimed" and hydrogen and carbon monoxide are left as products for output. This 'synthesis gas' then undergoes a process to turn it into fuel.

"The liquid hydrocarbons that come out of the Fischer Tropsch process can have a property or chain length that fits perfectly our fuel system on the airplane… this is why it's called a 'drop in' fuel, a fuel that can substitute fossil kerosene," Sizmann said.

Sizmann added that the process was "green in a philosophical sense" with sunlight as the primary source of energy, and that improving efficiency was now a key goal.

Going forward, hopes are high. "We were trying to produce the exact same fuel so we will be able to use the exact same infrastructure and the same aeroplanes that we are using today," Christoph Falter, a researcher at Bauhaus Luftfahrt, said.

"We expect… this new fuel, this solar jet fuel, to perform a little bit better than the conventional fuels that we're using today because the energy content is higher," Falter added, before going on to say that the fuel's "climate impact" could also improve.