🌱Macroalgae
Running Tide explored using macroalgae to capture carbon dioxide directly from the surface ocean. Just like plants, macroalgae uptake CO2 for growth, storing that carbon as biomass. That carbon-rich biomass can be sequestered by exporting it to the slow cycle - sinking it to sufficient depth or burying it in sediment.
We invested in a number of research programs to develop a macroalgae mCDR system. First, we had to prove that we could cultivate and grow macroalgae in the open ocean. Then, build the knowledge to optimize and scale the system and understand the potential environmental impacts and co-benefits as outlined in our Research Roadmap.
There were a few key practical problems that needed to be addressed first:
Can we prove that macroalgae grows in the open ocean where nutrients are scarce?
What macroalgae species can be cultivated, scaled-up up in a production environment, and sporulated consistently and predictably to dramatically increase the number of individuals?
How many macroalgae spores/gametophytes/sporophytes would we need to seed each a ton of substrate or buoys?
What is the spore/gametophyte/sporophyte productivity of each unit mass of macroalgae? How much do we need to produce to reach buoy production estimates?
Can we effectively control the sporulation process and produce reliable amounts of spores, gametophytes and/or sporophytes from the macroalgae biomass at any time?
How might we attach macroalgae spores to different types of substrate or buoys? And how consistently do attachment techniques result in blade growth?
If attachment is successful, does the attachment survive high-energy waves in the open ocean?
How can we test seeding and attachment in the lab to accelerate data collection and learnings? Can we simulate a high energy ocean environment - waves, sunlight, and currents?
The following pages detail our efforts to harness the natural carbon-sequestering abilities of seaweed to combat global warming and ocean acidification.
Ultimately, our research focused on cultivating macroalgae species like Ulva lactuca and Saccharina latissima (sugar kelp) and deploying them on buoys in the open ocean. We aimed to scale up production to remove significant amounts of CO2 from the atmosphere. Our broad, multifaceted program covered species and population selection, genetics, open ocean growth experiments, cultivation and scaling techniques, biogeochemical and macroalgae growth modeling, innovative methods for sporulation and substrate attachment, and growth / biomass measurement systems with custom hardware.
Program Outline:
Species Selection: The initial species chosen for cultivation by the Running Tide macroalgae program management team were: Ulva lactuca a common green alga, Ulva fenestrata, a Northern Atlantic green algae closely related to Ulva lactuca, and Saccharina latissima, commonly known as sugar kelp. These species were selected based on their availability, well-documented life cycles, compatibility with cultivation systems, and scalability. Their selection was strategic, aiming to maximize efficiency and output while ensuring sustainability.
Open Ocean Macroalgae Growth Deployments: Overall, we can confidently say that we observed increases of macroalgae coverage on cotton hanks deployed in the open ocean. This marked, to our knowledge, the first time Ulva fenestrata or Ulva lactuca has been proven to successfully grow in the open ocean. These successful research deployments establish a baseline performance of our macroalgae product (macroalgae + substrate + operational logistics) in a given oceanic location over time, setting an important starting point in an iterative, multi-year product development cycle and uncovering opportunities for improvement in our system design. During these experiments, we deployed proprietary hardware sensors to collect daily images, GPS coordinates, and ocean temperature.
Cultivation and Scaling: Running Tide’s approach to cultivation of macroalgae started by applying techniques commonly known in kelp farming. Over the last few years with more acquired knowledge and adoption of biotechnological cultivation systems and practices, the sophistication of the cultivation increased dramatically. Cultivation of selected species took place at numerous locations, while scaling of cultivation in large volumes took place at our research and production facility “Alda” in Akranes, Iceland. Scaling of cultivation was not required for many of our experiments, but it would have been essential for successfully seeding substrate/buoys for large scale deployments out of Iceland.
Modeling: Developing hybrid models for the cultivation of Ulva in PBRs offers significant potential gains by combining mechanistic insights and data-driven techniques to optimize key process variables such as pH, starting density, age of Ulva, and CO2 administration. These models may enhance predictive accuracy and robustness by integrating scientific principles with empirical data to capture complex interactions. By simulating various scenarios and identifying optimal conditions, hybrid models can maximize biomass yield, improve resource utilization, and ensure the sustainability and economic viability of Ulva cultivation. The iterative process of validation and refinement ensures continuous improvement, making hybrid models a powerful tool for advancing the efficiency and productivity of algae cultivation systems.
Sporulation, Seeding, and Attachment to Substrates: Effective sporulation of Ulva biomass was key to Running Tide’s scalable approach. Massive quantities of individuals can be generated through sporulation. Over the course of 2023 and into 2024 the team refined Ulva sporulation protocols and even learned to utilize the effect of the moon cycle on sporulation efficiency (see Macroalgae at Alda: 2023 Annual Report and Q1 2024 Report for details). We explored different techniques to ensure adequate attachment of spores to substrates and tested spore survivability during handling tests designed to simulate deployment processing steps.
We are proud to have successfully demonstrated Ulva growth in the open ocean, developed cultivation systems that scaled across geographies, and refined sporulation protocols to produce billions of algae spores. The following reports highlight Running Tide's cutting-edge research facilities, cross-disciplinary collaboration, and the challenges faced in scaling up this promising CDR technology.
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