In their effort to find an alternate and cost-effective fuel, scientists at the Indian Institute of Science (IISc) have found it possible to extract oil from a type of single-celled microscopic algae ‘diatoms’ by housing them within ‘biological solar panels’.

The scientists proposed creating a biological solar panel, which will contain diatoms instead of photovoltaic cells. Diatoms would float about in a nutrient-rich water solution and produce oil when exposed to sunlight.

Diatoms are commonly observed as a brown skin coating submerged stones in rivers and lakes and as phytoplankton in seas and oceans, typically contain oil droplets inside their cells, quite similar to petroleum.

The oil is a food source for the plants in lean times. Scientific analysis of diatom oil has shown that it is very suitable for use as biofuel.

“We propose altering cells of the diatoms so that they actively secrete oil droplets. We propose milking of diatoms without killing their cells similar to secretion of milk by selective breeding of cattle and alter their environment to maximise the rate of milk secretion,” TV Ramachandra of Centre for Ecological Sciences at IISc said from Bangalore.

The latter could be thought of as a solar panel that converts photons to gasoline rather than electricity or heat. Diatoms already secrete silica by exocytosisa biological process by which cells direct secreted material outside the cell walls. If diatoms could be made to similarly secrete the oil they produce, then it could be easily harvested, Ramachandra said.

He and his colleagues Durga Mahapatra and Karthick Balasubramanian from IISc along with Richard Gordon, a radiology professor at the University of Manitoba in Winnipeg, Canada are talking about the solar panel that could extract this oil instead of producing electricity.

Ramachandra and Gordon, whose collaborative work appeared recently in the journal Industrial Engineering and Chemistry Research, came up with some astonishing facts that nearly 25 per cent of the body weight of diatoms is purely oil, and that the figure goes up to 35 to 40 per cent when the organisms are starved of nitrogen.

In contrast, only 5 per cent of the biomass of oil-bearing plants such as soybean and oil palm, which are widely used to produce biofuels, is oil. Diatoms unlike other oil crops have an extremely high rate of growth. Some species can actually double their biomass within five to 24 hours, Ramachandra said.

Scientists have estimated that a hectare of diatom cultivation can yield 30,000 litres of oil, which is 100 to 200 times greater than the capacity of soybeans.

Ramachandra insisted about the advantage of the diatom solar panel and said that it can be created and maintained with equipment and methods that are inexpensive. This is different from photovoltaic solar panels, which require sophisticated fabrication facilities.

In tropical countries like India with an abundance of sunlight, biofuel-producing solar panels containing local diatoms could be placed in every village, Ramachandra said.