Is Algae The Next Sustainable Biofuel?

Algae have all the right ingredients for turning carbon dioxide into biofuel, but the precise recipe still needs to be created.

A blanket of algae covering a pond or lake often spells trouble for any organisms living beneath. Yet René Wijffels at Wageningen University in the Netherlands is attempting to create just such a mat of green. His aim is to reduce the cost and energy consumption of algae biodiesel production.

Biofuel has long been seen as a potential replacement for petrol. Oils from land plants and algae can be processed to create a range of combustible fuels including biodiesel. And because new growth of plants and algae consumes carbon dioxide, it is hoped that these fuels will be carbon neutral.

Unlike other biofuel sources, algae do not need land that could otherwise be used for food crops. They can be grown on arid land in salty or waste water, and can even absorb CO2 from the flue gases of power plants. What’s more, algae grow much faster than land crops and can produce up to 20 times more oil for a given area. So says Beatrix Schlarb-Ridley of the InCrops Enterprise Hub at the University of Cambridge.

Attempts to create fuel from algae so far, however, have not been as environmentally sustainable as hoped. Algae are grown in ponds or a variety of transparent reactors that keep the algae in water while exposing them to sunlight. The problem is, some of these reactor designs consume more energy than they generate and produce unacceptable amounts of CO2. “If you produced microalgae today for biofuel production, with most of the technologies you would have a ‘negative energy balance’, and actually would produce more CO2 than fossil fuels,” says Wijffels.

In a bid to reduce these emissions, Wijffels is trying to cut the energy needed to harvest the algae before the oil is removed from it. In open ponds, this can account for up to 80 per cent of the energy consumed by the entire production process, in large part because the organisms are floating individually in large amounts of water.

Algae can be encouraged to clump together, using flocculants, to make it easier to retrieve them from water by centrifuge. But this adds considerably to the cost of production, and the flocculants must be removed before the algae can be refined.

So instead, Wijffels is attempting to use algae to promote clumping. He has added flocculating strains of algae, such as Ankistrodesmus falcatus, to a reactor containing the oil-producing strain Chlorella vulgaris, and found the two types readily joined together in clumps.

“You can have co-cultures of microalgae, in which one of them is really good at oil accumulation and the other one is really good at sticking to the other algae,” he says. “The art, of course, is to have a large percentage of oil-producing algae and a very small percentage of those flocculating algae.”

To get a better insight into the financial and energy costs of production, Wijffels aims to test the technique at Wageningen University’s Algae Production and Research Centre. AlgaePARC was launched earlier this year and allows algae-production processes to be tested alongside each other under the same conditions. It is supported by companies including ExxonMobil, Total, and biologist Craig Venter’s firm Synthetic Genomics. It has an open pond and six outdoor bioreactors made from horizontal tubes, vertical tubes or flat panels.

Ultimately though, if algae biofuel is to be made financially and environmentally sustainable, we will need to make use of more than just the oil produced by the organisms, says Schlarb-Ridley, who authored a report earlier this year on research into algae for the UK’s Biotechnology and Biological Sciences Research Council.

“Even if you are able to produce algae on a mass scale, you still need to use the by-products as well as just the fuel,” she says. Fortunately, as well as being oil producers, algae are also a valuable source of protein for fish and animal feed.

In a similar way, algae can use the by-products of other industries, says Schlarb-Ridley. Algae reactors could be connected to farms or fisheries, to consume the nitrate-rich waste they produce. Algae can also mop up the CO2 from flue gases from nearby industrial plants.

View original article at: Is Algae The Next Sustainable Biofuel?

unnamed2

 

Leave a Reply