Developing biodegradable seeding strings for a cleaner seaweed industry

January 15th, 2026 | Testing at sea

Seaweed farming faces many of the same plastic-related challenges as aquaculture and fisheries. This is why SFI Dsolve is now investigating new biodegradable materials that can break down naturally in the ocean—without compromising growth or product quality.

Why new materials are needed

Today, plastic-based seeding twines are used to attach seaweed seedlings (juvenille sporophytes) to cultivation lines (carrying lines). While they work well during the early establishment phase at sea, they can become problematic at harvest. During harvest, the thin rope can easily be cut or damaged, increasing the risk of small plastic fragments ending up in the final product. It must also be removed from the carrying line after harvest, adding to manual labour and overall costs.

Biodegradable seeding twines may offer a solution. Once the seaweed is firmly attached, the material can break down naturally, leaving a clean main line that is far easier to reuse—and a raw material free from plastic residues.

What characterises a good seeding string?

To function effectively in seaweed farming, a biodegradable seeding string must be able to both capture and hold the young sporophytes, ensuring they establish well at sea. The material must also be strong and elastic enough to withstand stretching of the carrying line it is wrapped around. Additional requirements include being safe for food contact, non-toxic, affordable, and available in commercial quantities. Without reliable large-scale availability, even the best materials cannot be adopted by industry.

What do the tests show so far?

Based on these requirements, researchers at SINTEF are evaluating which biodegradable materials offer the best combination of attachment ability, growth performance, strength and suitable degradation time. The goal is to identify solutions that can be deployed at an industrial scale and help reduce plastic use in the seaweed sector.

Early results indicate that cotton, viscose, wool and a nettle-based design are among the most promising candidates. The next step is to deploy them at sea to test biomass yield and degradation. Additional alternatives will also be evaluated, such as the “Seaweed Twine” developed by Viable Gear specifically for seaweed cultivation.

Cotton, viscose and wool show promising growth results. These are among several biodegradable materials being tested further in Norwegian seaweed cultivation. Photos: SINTEF

A step toward a cleaner and more efficient industry

Biodegradable ropes have the potential to reduce plastic use in marine industries, simplify operations and strengthen food safety. With successful development, these materials could give the Norwegian seaweed sector an important competitive edge in a rapidly growing global industry. Small components—big impact.