Purple Slime and the Fuelabolic pathway

Producing tunicates commercially

A group of resilient Norwegian researchers have been cultivating tunicates experimentally at a pilot facility in Øygarden, a small island community near Bergen.

The production method resembles the cultivation of mussels. At a facility in a small finger of a fjord, long plastic sheets are anchored to the seabed and held vertical by buoys. Between these sheets flows seawater teeming with the microorganisms tunicates need.

The Research Council of Norway’s program FORNY2020 and the technology transfer office Bergen Teknologioverføring are investing to scale up tunicate production, and allocating NOK 8.7 million in funding to the tunicate project through 2014. Christofer Troedsson of the University of Bergen’s Department of Biology is the project manager.

Reaching commercial yields

“Our single greatest challenge is cultivating enough biomass per square metre to make operations profitable,” explains project manager Troedsson. “We anticipate a crop of 100 to 200 kilograms per square metre, which is an extremely high yield. But that is what is needed for profitability because the price per kilo is so low.”

The Bergen-based researchers have achieved this production target at their small-scale facility, and the mathematical models they have run make them optimistic that a similar production level is possible with large-scale tunicate farms. But there are no guarantees just yet.

Dewatering and harvesting

“The second major challenge we face is how much water we can squeeze out of the tunicates,” continues Dr Troedsson. “Their body mass is 95 per cent water. To sell the product we have to be able to remove at least 90 per cent and preferably 95 per cent of that water by mechanical pressing.”

“On an isolated basis we have managed to mechanically press out 97 per cent of the water. Now we must try to carry out that process efficiently on board the harvesting boats, while at the same time pulling several tonnes of tunicates per hour out of the sea.”

“Thus production volume and water separation are the two critical factors that must be successfully addressed if tunicate cultivation is to be profitable for private companies in today’s market,” concludes Dr Troedsson.

In today’s Digest, we explore the bottom line of tunicates and multi-step systems — food for today, or tomorrow – or food for thought? – all via the page links below.