Researchers get closer to creating an algae bioreactor


The algae production unit at Wageningen University

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Intreegue Photography

Under the right circumstances, tiny algae can grow at extreme rates, making various sustainability applications more feasible. Researchers at Wageningen University are identifying new methods of producing algae, in hopes of moving to a full-fledged bioreactor. However, it was not easy.

Outlying islands tend to face a unique challenge: they are almost never self-sufficient. Many essentials – from food to fuel – have to be imported from abroad. This makes the islands extremely dependent on other countries and of course also results in a lot of CO₂ emissions from container ships.

What if you could produce some of these products on the island in a sustainable way? Wageningen scientists have developed such a production process using microalgae. These little powerhouses – most are even smaller than a single red blood cell – can multiply at extreme rates under the right circumstances. Where a one-hectare oil palm plantation produces around 6,000 liters of oil per year, a seaweed grower can expect to produce around 35,000 liters in the same period.

people standing near outdoor algae bioreactor
Researchers hope to use microalgae as a sustainable energy source for remote islands

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WUR

Fish food and meat substitutes

The good thing is that these microalgae are also a good source of fats and proteins. This means that innovative applications become feasible, explains professor of bioprocess engineering René Wijffels. “For example, you can convert microalgae into biofuels to make flights to and from islands sustainable,” he says. This production process is currently still too expensive, but many other applications are already possible in the short term. Microalgae are very suitable as sustainable food for fish farms or as meat substitutes, for example.

In recent years, Wijffels and his colleagues have been looking for a place to produce these microalgae on a large scale. They built a test bioreactor on the island of Bonaire, partly at the request of local authorities. They then set out to find a “closed system”: an algae bioreactor operating entirely with locally available raw materials. Wijffels: “Algae are very suitable for this, because they mainly need seawater, CO₂ and sunlight. These are inexhaustible raw materials that are present in abundance on tropical islands.

Stay cool

Two people standing next to a V-shaped bioreactor
Researchers Barten and Chin-on at the Bonaire Algae Bioreactor

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WUR

But the path to a full-fledged algae bioreactor comes with its challenges. The researchers gradually came up against a serious scientific obstacle: microalgae do not like high temperatures. If the temperature in your algae bioreactor increases too much – a real problem on a tropical island – the crop is lost. You can, of course, cool the bioreactor, but that costs a lot of water and electricity, which doesn’t fit the ideal picture of a sustainable closed system.

In recent years, two PhD students – Robin Barten and Rocca Chin-on – have been researching ways to make seaweed suitable for Bonaire’s tropical temperatures. First, in the Wageningen laboratories, Barten studied which type of microalgae has the greatest resistance to heat. After a rigorous selection process, he arrived at Picochlorum sp.a microalga naturally present in Bonaire.

“It is a very robust microalgae with good tolerance to high temperatures and salt concentrations, and it is furthermore one of the fastest growing microalgae in the world,” says Barten. “It’s also great that this is already happening in the environment, because you don’t want to run the risk of introducing a different type of algae into the wild.” As an added benefit, Picochlorum sp. consists of up to 50 percent nutritious protein.

Through a process of evolution, Barten has made the Picochlorum sp. even stronger. For a year, he produced “his” type of algae at slightly higher temperatures each time. Most of the algae died in this experiment, but Barten was only interested in the few survivors. By repeating this experiment several times, he finally ended up with the algae which are very resistant to heat.

Barten: “Through this selection process, Picochlorum sp. can now withstand about 2.5 degrees of additional heat. Microalgae can now survive up to 47.5 degrees Celsius, but grow fastest around 40 degrees Celsius.

In the meantime, Chin-on has been working in Bonaire on a new prototype of the bioreactor, the test facility in which the algae are grown. Cooling also plays a major role here. Chin-on decided to build the rearing system in a V-shape, so that the whole bioreactor could sit in the water if the temperature rises. The temperature in water fluctuates less than on land.

Chin-on: “It sits in water at around 30 degrees Celsius. This means that this bioreactor is also suitable for algae which is slightly less heat resistant than Picochlorum sp in principle.”

person recovering microalgae from a tank
Barten and Chin-on bred a strain of microalgae that can tolerate high temperatures

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WUR

Scaling remains a bottleneck

Although scientists have uncovered more and more secrets about algae production in recent years, scaling up a full-fledged algae bioreactor on Bonaire is still not easy. According to Wijffels, this is mainly a financial problem: there are few large companies on the island that can develop the Wageningen test facility into a profitable operation. Bonaire’s economy is mainly based on tourism, and there is very little big industry.

To solve this problem, Wijffels proposes to combine recent scientific breakthroughs into a fully functional demonstration model. This type of mini-bioreactor should convince investors – if necessary from other countries – to further develop algae production.

Wijffels hopes that authorities, companies or scientific funding bodies will be willing to fund this demonstration model. “It’s the best way to plant a seed,” says Wijffels. “Ultimately, this is also in Bonaire’s interest because it means the island can become more self-sufficient and the economy more diversified. The concept can then be applied to other locations: Bonaire can be used as a model laboratory for this sustainable circular technology. »

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