Flying on algae

Various alternatives are being tested for road vehicles, including biodiesels, fuel cells and electric batteries.

It is difficult to imagine any of these fuels being suitable for commercial airliners, since most have comparatively low energy densities and much greater volumes of fuel would be required in order to replace an equivalent volume of kerosene.

Additionally, airline fuel has to withstand the rigours of large temperature variations during flight as temperatures can typically be -20 degrees centigrade at cruising height, and as high at 45 degrees centigrade at airports in hotter countries.

A couple of weeks ago, a new fuel mixture using 50per cent of kerosene and 50 per cent of a new bio-fuel was successfully tested for the first time in a twin-engined Continental Airlines aeroplane.

The bio-fuel was derived from algae and the success of the test perhaps pointed to a credible alternative to traditional jet-fuel.

Developing bio-fuel from algae offers a number of advantages over other forms of bio-fuel.

The species of algae that is being used in the process is lipid rich (in other words full of fat!) and grows in shallow waters that would otherwise be unsuitable for other forms of agriculture.

These waters could include coastal zones, deserts and even waste water from sewage works.

This would mean that unlike rapeseed, soyabean or palm oil, it is unlikely that food-based agriculture will suffer as a result of crops being grown for fuel purposes.

But unlike traditional types of crop, algae growth is very difficult to control and harvest efficiently.

One particular obstacle is how to grow algae on a large scale, since many of the strains already grown are not yet robust enough to withstand conditions such as the pH of the water, temperature, invasion from other algal species and the possibility of disease.

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