Seagriculture EU

21 - 22 June 2023

Trondheim, Norway

Resolving ‘offshore’ aquaculture: the distinct effects of distance and exposure energy on the levelized cost of seaweed

Tobias Dewhurst, Ocean Engineer, Kelson Marine, USA

About the speaker: 

Dr. Tobias (Toby) Dewhurst leads the ocean engineering firm Kelson Marine Co. He is an experimental and numerical hydrodynamicist who specializes in the interaction of floating structures with waves and currents. He has led industry and research projects in ocean renewable energy and open-ocean finfish, shellfish, and macroalgae aquaculture and is active in both research and development of tools, methods, and solutions for challenging ocean engineering applications. His mission is to make high-quality ocean engineering accessible to low-margin blue economy industries.

Company info:


Born on New England's working waterfront and leveraging years of ARPA-e funded research and development, Kelson Marine uses rigorous metocean and risk analysis and field-validated, model-based engineering tools to deliver cutting-edge marine systems at the speed of innovation.

By combining advanced engineering knowledge and technology with firsthand experience on the sea, Kelson delivers safe and reliable systems for aquaculture and marine renewable energy.


Cultivation structures, ocean engineering, risk mitigation, metocean analysis


1. When was the first time you got involved with seaweeds and why?

In 2013 I shifted my focus from the physics of wave and tidal energy devices to the hydrodynamics of flexible aquaculture structures. In 2017, I was asked by several groups to support their research and development of low-cost, large-scale seaweed cultivation structures under the US Dept. of Energy’s ARPA-e MARINER program. Along the way, we got to study the unique hydrodynamics of seaweeds, develop software tools to understand how kelp farms respond to waves and currents, and validate those tools against full-scale measurements of mooring loads on open-ocean seaweed farms. Since then, we’ve gotten to apply our knowledge in developing and de-risking farms around the world.


2. What is your view on the European seaweed industry in 2030?

I have very little insight into how far the industry will grow by 2030. But I do know that there’s a lot we can do to develop cultivation structures that are safe, high-yield, and economically feasible.


3. What will you be talking about at Seagriculture EU 2023?

I’ll be sharing results on how a site’s exposure energy and distance from shore affect the cost of seaweed. I’ll report the ICES Working Group on Open-Ocean Aquaculture’s recommendation to resolve ambiguity in the term “Offshore aquaculture” by distinguishing between distance from the baseline and “exposure” as measured by a physical index; I’ll show results from field validation of predictions of forces on large-scale seaweed farms using open-source tools; and I’ll give results on the levelized cost of seaweed for food and carbon as informed by those validated models.