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Swimming power plants

So. What is the economic importance of slime? The answer is: huge, and growing! Slime on the surface of a pond might not be attractive. But these are algae. And algae are astonishing. Though individually often no more than a few micrometers long – similar in size to bacteria – the prodigious volumes to which they can grow mean that algal blooms in the world’s oceans are visible from space.

They are among earth’s simplest life forms, yet without them most other life on the planet would be at risk, as micro-algae produce approximately half of our atmospheric oxygen. They are among the most robust forms of life, being able to grow almost anywhere including deserts and seawater. And they are among the most enduring: fossilized algae discovered in India have been dated back 1.7 billion years. No-one knows how many varieties of algae there are, but the American National Museum of Natural History in Washington DC has a collection of more than 320,000 varieties. And mankind uses them in an enormous number of ways.

The Aztecs ate them. We still eat them today – from sushi to food supplements. Algae contain all the essential amino acids, high amounts of simple and complex carbohydrates, an abundance of vitamins, minerals and trace elements. The health benefits claimed for omega-3 fish oils are in fact derived from algae as oily fish such as salmon don't actually produce omega-3. Instead they accumulate their omega-3 reserves by consuming micro-algae.

Different uses

Algae are used to reduce cholesterol. They are used in ice cream and face cream, in toothpaste and shoe polish. They have been used as fertilizers and soil conditioners for centuries. They can be used to bind heavy metals. But what are they? Algae are plants. Seaweeds are types of algae, and kelp seaweed varieties can grow up to 50 meters long. More often, though, algae are microscopic single cell organisms with no roots or stems or leaves. Like other plants, however, they mostly grow by photosynthesis. And the application of biotechnology to micro-algae is where they get really interesting. Algae live on a diet of carbon dioxide and sunshine, which they convert into oxygen and biomass – a combination of fats, carbohydrates and protein. They can be farmed, and once they have been harvested oil can be extracted from them.

Considerable research is currently taking place into their use in the production of biodiesel. Aircraft fuel is already being produced from them by the US military, and has been used by several commercial airlines. The reputation of first generation biofuels suffered as a result of the conversion of prime agricultural land from growing food crops to growing fuel crops. But algaebased fuel is one of the second generation of biofuels which show great potential. It has been claimed that algae could produce up to 300 times more oil per acre than conventional crops such as rapeseed, palms and soybeans; and harvesting cycles can be between one and ten days. Crucially, algae can be grown on land that is not suitable for other crops, including arid and excessively saline soils, and offer the prospect of being able to convert a variety of pollutants into valuable products. They can be fed on waste water – including sewage – and could use the CO2 produced by other industrial processes, such as cement and steel manufacture. Algae-based fuels are essentially carbon-neutral. While they do not reduce atmospheric CO2 – because any CO2 taken out of the atmosphere by the algae is returned when the biofuels are burned – they would eliminate the introduction of new CO2 by displacing conventional hydrocarbons.

Fuel production

Furthermore, once the oil has been extracted from the algae, the remaining matter could be used in the production of other fuels. It can, for example, be digested to make methane; or burned as a biomass fuel in its own right for power generation; and it can be fermented to produce ethanol. In fact, the fermentation of algae to ethanol releases CO2, which could be used to grow more algae, and trials are taking place with such closed-loop systems. That might sound too good to be true, and the commercialization of algae-fuel is probably some way off. But slime is full of surprises!

GEA and algae

Having grown the algae, it is only of any value if it can be separated from the medium – water – that it is growing in. This process is called harvesting, and GEA Westfalia Separator, part of GEA Mechanical Equipment, has been supplying centrifuges for concentrating algae for almost half a century.

But the company has now designed a new generation of separators specifically for algae biotechnology. These separators can be used for processing small to medium capacities of farmed algae suspension (up to 24,000 liters an hour), providing gentle treatment for the sensitive cells and producing very high levels of dry matter. With specially developed classification decanters, GEA Westfalia Separator can now selectively separate special high-quality dyestuffs from the algae or even extrinsic algae from the original algae culture.

GEA Niro Soavi supplies homogenizers used in algae processing, while both GEA Niro and GEA Barr-Rosin supply varieties of equipment for drying algae. These dryers are used in the manufacture of products such as carrageenan, alginates and agar that in turn find applications in medicine and the pharmaceutical industry, and very widely in the food and cosmetics industries where they are used as thickening agents.