SINTEF Converting Seaweed into Biocoal

 Seagriculture EU 2024

The finished product: biocoal derived from seaweeds that can be used to improve soil, and which also stores CO₂. Photo: SINTEF

by Svein Inge Meland,

SINTEF, one of Europe’s largest independent research organizations, is planning to install a seaweed cultivation test facility in the Frohavet, a tract of open ocean located off the Trøndelag coast in mid-Norway. Seaweeds cultivated there will be converted into biocoal and used to improve agricultural land. A new method for carbon capture and storage is now in trial by Norwegian researchers.

Seaweeds have a remarkable ability to absorb CO₂, and, according to Jorunn Skjermo, a research scientist at SINTEF, we ought to be learning how to exploit this process. “Our current plans for emission reductions simply won’t be enough,” she says. “If we are to meet our climate change mitigation targets, we have no time to lose in removing CO₂ from the atmosphere.”

Carbon capture at sea

The process of making biocoal from seaweed will start on land with the cultivation of macroalgae seedlings on ropes. This will take place in labs at SINTEF in Trondheim and at a company based in the Netherlands, thus enabling comparisons to be made between two different approaches. In the autumn, the ropes will be installed at a cultivation facility in the Frohavet, a stretch of open ocean located offshore Fosen on the Trøndelag coast in mid-Norway.

Seaweeds grow slowly in the darker seasons, but as winter recedes and the days get longer, growth will accelerate. It is during this period of growth that the seaweeds absorb CO₂, and next summer they will be ready for harvesting.

Since the concentrations of carbon dioxide in the atmosphere and the oceans are in balance, carbon capture from the sea has the same effect as that from the air.

Locking in the carbon

Once harvested, the seaweeds are then dried before pyrolysis is used to convert them into biocoal. This is achieved by heating them to about 600 degrees in an oxygen-free atmosphere. This process serves to modify the molecular structure and stabilize the carbon. The resulting biocoal is resistant to degradation by fungi and microorganisms.

The pyrolysis stage will be conducted in laboratories at SINTEF Energy Research and at a commercial company. The effect of the biocoal on arable land will be tested at the Mære Agricultural College in Steinkjer.

Improving the soil

“Deriving biocoal from seaweeds both captures and stores CO₂, as well as resulting in a product for which there is a need,” says Skjermo. She is heading the research segment of a project that has been given the name Seaweed Carbon Solutions JIP (Joint Industry Project).

The addition of biocoal to soil is intended to help boost porosity and water binding capacity. It will also create favorable conditions for the growth of microorganisms. When biocoal is combined with a fertilizer product that is also derived from seaweeds, the mixture serves to supply the soil with useful nutrients.

Out at sea

The offshore seaweed cultivation facility comprises a network of powerful ropes, or hawsers, on which the seaweeds grow, suspended from large floats. The facility will be anchored to the sea floor. Most such facilities currently in use in Norway are located close to the shore, but there are many reasons why SINTEF wants to install the trial facility in the open ocean despite the likelihood of much harsher weather conditions.

“Modelling indicates that seaweed yields will be higher the further we are from the coast,” says Skjermo. “We’ll be getting more seaweed per meter of rope. This is partly due to the period with access to nutrient-rich water will be longer. Water temperatures are more stable and the salinity virtually constant,” she says.

Full-scale production in 2030

The test facility will cover an area of 650,000 square meters, with production expected to be in the region of 600 tons of seaweed, which in turn will yield 25 tons of biocoal. SINTEF has calculated that a facility one square kilometer in size will produce 20,000 tons of seaweed annually, equivalent to the capture of 3,000 tons of CO₂.

“I believe that it is realistic to upscale this approach to an industrial facility by 2030,” says Skjermo.

SINTEF’s partners in this project are DNV, Aker BP, Equinor, Wintershall Dea and Ocean Rainforest, which is a company based in the Faroe Islands that combines seaweed cultivation with the construction of cultivation facilities. The project has a budget of NOK 50 million ($5 million USD).

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