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Algae as a source of biofuel?

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A race is on to establish a commercial biofuel industry based on algae. A leading contender is eWater CRC Partner South Australian Research and Development Institute in Adelaide (SARDI), which has recently opened a new $5 million photobioreactor facility at its Aquatic Sciences laboratories.

Project leader Dr Sasi Nayar (SARDI) examines a flask of algae.Project leader Dr Sasi Nayar (SARDI) examines a flask of algae.

Single-celled algae are wonderfully efficient at taking carbon dioxide and sunlight and turning it into an oil-rich biomass, which can then be refined into fuel. If the process can be performed on a massive scale, then it could become the oil well of the future. The attraction of algae is that they will grow wherever nutrients are available, even in waste or saline water.

Through photosynthesis, these single-celled organisms fix carbon dioxide into carbohydrates and then into a variety of complex organic molecules, including lipids (fats and oils). It is these lipids that become the feedstock for biodiesel.

The usual pathway to biodiesel is to react the lipids with alcohols in the presence of a catalyst to make fatty acid methyl esters, a well-known process called transesterification. A byproduct is glycerol, which is also a valuable commodity.

Algae facts:

  • Single-celled algae, or microalgae, are tiny organisms which, like plants, use photosynthesis to convert the sun’s energy into chemical energy.
  • Microalgae can be grown in large vats (bioreactors) that provide the algae with ideal conditions for growth and oil production.
  • Microalgae are much more efficient at converting sunlight into biomolecules because they grow in suspension, meaning they have ready access to water, carbon dioxide, and nutrients.
  • The total oil content in algae can be up to 60% of their dry weight.
  • Microalgae can produce more than 30 times the amount of oil (per year per unit land area) than oil seed crops.
  • Biodiesel is a renewable replacement to ordinary petroleum diesel.
  • Biodiesel is non-toxic and biodegradable.

A raceway tank for growing algae.A raceway tank for growing algae.

The final biodiesel product is a clean-burning alternative to fossil diesel fuel. It is highly biodegradable, non-toxic, environmentally friendly, and can be produced at a competitive price. Currently, biodiesel is produced from oils of plant or animal origin, including canola, soybean, palm, and rapeseed oil or from tallow, non-food oil crops, and used frying oils including your local fish and chip shop.

Australia is well placed to develop this technology because it has extensive marginal land unsuitable for agriculture, large reserves of saline groundwater and abundant sunlight. Yields of oil from algae can be up to 60 per cent of their dry weight, and on the basis of area can be 10 times higher than from terrestrial crops like canola. Calculated over the full production cycle, algae-derived diesel emits around 70 per cent less greenhouse gases than normal diesel.

"Replacing just 10 per cent of Australia’s transport fuel with biodiesel from algae would reduce CO2 emissions by nearly four million tonnes...

...Unlike ethanol from sugar cane, the oil would not use up human food supplies.

Harvested algae, ready for extracting its oil.Harvested algae, ready for extracting its oil.

The microalgal growth facility in Adelaide allows researchers to optimise growth rates, under controlled conditions, in specially designed reactors and raceways. One of the facility’s major users is the Algal Fuels Consortium (AFC), a collaboration involving SARDI, Flinders University, and CSIRO. Chair of AFC, Associate Professor Rob Thomas, who has been researching algal biofuel production at SARDI since 2006, says the facility will raise research into biofuels to a whole new level.

The next step is for AFC to build a pilot plant on Torrens Island near Adelaide. AFC has received a Second Generation Biofuel grant of $2.7 million from the Department of Resources, Energy and Tourism towards the construction and operation of the plant, which will be commissioned in 2011. The idea is to use nutrient-rich saline water from the nearby Port River estuary, carbon dioxide from adjacent power plants, and Adelaide’s abundant sunshine.


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