Algae and wind power will power Scottish bioreactors – and feed salmon

Tereza Pultarova

A Scottish salmon farm (Credit: Shutterstock)
A Scottish salmon farm (Credit: Shutterstock)

What do renewable energy, salmon farming and algae have in common?

Very little so far but that may soon change. A Scottish biotechnology company called Xanthella envisions that these three things could soon form a tight circle that would help Scotland’s burgeoning windfarms maximise their potential and at the same time allow local aquacultures to feed salmon, one of Scotland’s most valuable export items, in a more sustainable way. 

As part of the Aslee (Algal Solutions for Local Energy Economy) project, funded by the Scottish government, the company has installed 16 1,000-litre photo-bioreactors at the Ardnamurchan Estate in the west of Scotland, in which it will grow algae using renewable power from a local wind turbine.

“We want to see whether we can use algae production locally as a way to completely smooth out wind electricity production to prevent the wind turbine from being curtailed off as often happens when it’s too windy for the local grid,” said Douglas McKenzie, Xanthella’s managing director and founder. 

“Renewables are being deployed in Scotland much faster than we expected. We could generate super abundance of electricity but we need to have some sensible use for it because the grid couldn’t cope with it.”

The idea is simple. When electricity is needed in the wider grid, the renewable resources would feed the grid. Then, when the grid can’t take any energy because too much is being produced, the electricity from the turbine or a solar plant would power the photo-bioreactors, in which the algae would grow through photosynthesis. 

Sustainable goals

“For phototrophic production of algae, you need a lot of light,” said McKenzie. “That requires a lot of electricity, which means the reactors can absorb quite a lot of the load.”

The photo-bioreactors are fitted with submerged LED light sheets. They are fastened in a metal racking system and attached to the supply of water and power, as well as drainage pipes. Tying in all the major elements of the Scottish economy in a sustainable fashion, the engineers want to feed the algae whisky production co-products from a nearby distillery. 

In previous laboratory experiments with a smaller 700-litre photo-bioreactor, the researchers found that, in fact, the algae would benefit from the intermittent nature of the renewable power supply since they grow better when periods of light alternate with periods of dark – just like in nature. 

“The interesting thing is that it doesn’t really matter when you give them the darkness,” said McKenzie. “That makes the technology really useful as a grid balancing tool because you can give them the power at the time when it is the most beneficial to do so.”

McKenzie said that the reactors can be turned on promptly without any preparation, which makes them convenient as a tool for balancing the voltage and frequency in the wider grid, which is affected by the fluctuations in renewable energy generation. The amount of light produced by the LED panels in the bioreactors varies depending on how much electricity is coming through, allowing for the technology to flexibly adjust to the needs of the grid in any given moment. 

“There are not that many industrial processes that you can think of that match that,” McKenzie said. “Right now, the National Grid has to pay companies to be able to reduce power consumption on demand. Having something that could increase power consumption on demand would be very useful too.”

Nutritious answers

In the context of Scotland, there is a solid business case for growing algae, according to McKenzie. While using algae for the production of biofuels and bioplastics still isn’t economically viable, the green microorganisms also produce omega-3 fatty acids, which could be used either to manufacture nutritional supplements for humans or be fed to salmon in the many Scottish fish farms. 

“At the moment the omega-3s used in salmon farms come from fish oil,” said McKenzie. “We are catching lots of anchovies off Peru, turning them into oil and putting them into salmon. The industry recognises this is not a viable approach and is interested in finding other ways of manufacturing omega-3s.”

The UK salmon industry would easily absorb hundreds of tonnes of microalgae every year, McKenzie said.

Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.

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