At a time when daily news headlines paint a bleak picture for our planet, seaweed farming offers hope. As scientists search for ways to combat the climate crisis and policymakers focus on coastal communities, seaweed’s potential to improve ocean health and create equitable opportunities has gained widespread attention. A potential game changer, seaweed is macroalgae that have been harvested across the world for centuries. To ensure the many benefits of seaweed are realized, government action at all levels is necessary—whether for the permitting process or funding research to ensure a sustainable farming industry focusing on small-scale and Indigenous farms. Seaweed farming is a unique opportunity that can benefit local communities while tackling the climate crisis.
Seaweed farming—not to be confused with harvesting wild seaweed—is a burgeoning industry in the United States with many practical benefits. As it grows, seaweed removes carbon from the ocean and dissolved nutrients that pollute waterbodies. Seaweed requires no inputs like feed or pesticides. And seaweed farming provides a variety of business opportunities. According to the National Oceanic and Atmospheric Administration (NOAA), seaweed farming is currently the fastest-growing aquaculture sector. Seaweed is a versatile product and is used for food, feed, fertilizer, cosmetics, and pharmaceuticals. Scientists are exploring additional uses for seaweed, including using it as a potential Per- and polyfluoroalkyl substances (PFAS) alternative in food containers. See Lori Valigra, Maine Scientists Are Testing Tree Pulp and Seaweed as PFAS Alternatives, Bangor Daily News, May 6, 2024.
Indigenous communities have been farming seaweed for millennia, and it is their practices and experience that serve as a foundation for current farmers. This article examines the current practice of farming native seaweed in the United States, with a focus on nearshore farms in state waters (i.e., within three nautical miles of shore) and a comparison of three states’ regulatory schemes. Although this article focuses on state approaches, local government and federal agency approvals also may be required. We then explore potential benefits and challenges of such farming, concluding with lessons learned and considerations for the industry’s path forward.
To start a seaweed farm, seaweed spores from native parent plants are cultivated onto strings, and then farmers place the seedlings on longlines underwater at the farm site. The seeded rope is suspended four to eight feet below the surface of the water between two moorings, and the seaweed grows naturally throughout the winter without further attention. As the seaweed grows, it provides shelter for fish, which supports commercially important fish stocks and helps sustain diverse marine life. Once harvested, the specific processing techniques depend on how the seaweed will be used and may include cleaning, milling, drying, and blending.
Seaweed farming faces significant hurdles. Permitting frameworks vary across the United States, as does access to processing facilities and available coastline for farming. Coastal states have developed a patchwork of permitting and siting requirements that may greatly impact a farmer’s path to establishing a seaweed farm. In nearshore waters, state law controls. In some cases, the regulatory requirements are broadly applicable to all types of aquaculture, from fish and shellfish to seaweed, despite the fact that each type of marine farm has different concerns and benefits.
In Alaska, Alaska Natives, including the Haida, Tlingit, Tsimshian, Eyak, and Alutiiq people, have harvested and used seaweed for food and material for centuries. This is not surprising, as Alaska’s coastline is longer than that of all the other coastal states combined and has hundreds of native seaweed species. The primary seaweeds cultivated in Alaska are sugar kelp, ribbon kelp, and bull kelp. Its seaweed industry has grown exponentially over the past few years and ranks second, behind Maine, for the amount of seaweed produced in 2023. In 2019, farmers in Alaska produced more than 112,000 pounds of kelp, a 200% increase over the state’s first commercial harvest in 2017. See NOAA Fisheries, Seaweed Aquaculture (Feb. 28, 2024).
Alaska’s permitting framework for aquatic farming activities applies to shellfish (e.g., oysters, mussels) and aquatic plants, including seaweed, and involves multiple state agencies. The Alaska Department of Natural Resources (ADNR) oversees the placement of aquatic farms on state tidal and submerged lands by issuing 10-year leases, while the state’s Department of Fish and Game oversees the operation of such farms by issuing an operations permit. Additionally, Alaska’s Department of Environmental Conservation regulates aquatic products if such products are processed (e.g., dried, frozen, packaged) for human consumption.
Although an ADNR joint-agency permit application is intended to streamline the process for aquaculture, the agency can become backlogged, delaying commencement of seaweed farming. Depending on a number of factors (e.g., workload, complexity of the proposed farm), it can take up to two years to obtain an ADNR lease for aquaculture activities. State legislation attempts to address this delay by funding more staff to review permit applications and reducing regulatory hurdles.
Harvested seaweed is mainly used for food in Alaska. Barnacle Foods is a leading company in this area, producing seaweed-based hot sauces, kelp pickles, and kelp seasonings. Alaska’s Indigenous communities continue to take part in seaweed farming as well. The Native Conservancy offers a Regenerative Fund to support Native seaweed farmers in Alaska, as well as providing technical assistance and training to help navigate Alaska’s permit system and grow, harvest, and process kelp. In addition to establishing its own farm, the Native Conservancy advocates for the state to prioritize permitting Native seaweed farmers seeking to restore traditional cultural practices over out-of-state corporations building massive farms.
Cold storage is necessary to ensure food safety, but climate change is preventing Alaskans from relying on permafrost to keep harvests from spoiling. Additionally, given that seaweed farms can be located far from cities and manufacturing areas, it is essential to build processing facilities near farms to connect the product to domestic markets both within and outside of Alaska. Transportation costs can be quite high and can affect a farm’s profitability and the end use of its harvest. Despite these challenges, Alaska is investing in seaweed farming. Settlement funds from the 1989 Exxon Valdez oil spill are being used for mariculture research and development, along with funding from the University of Alaska. See Yereth Rosen, Seaweed Farming Inspires High Hopes in Alaska for Economic and Environmental Benefits, Alaska Pub. Media (Mar. 13, 2023).
In the lower 48 states, Maine—with a longer coastline than California—is the leader in seaweed farming, with more than one million pounds of seaweed harvested in 2023. In fact, Maine boasts the first commercially viable kelp farm in the country, dating back to 1974. Over the last four decades, the industry has continued to grow—currently there are more than 40 active commercial seaweed farms. See Sea Grant, State of the States: Status of U.S. Seaweed Aquaculture (presented at the 2023 Nat’l Seaweed Symp.). Similar to Alaska, Maine kelp farmers are experiencing an uptick in production, and one of the primary seaweeds cultivated in Maine is sugar kelp, followed by skinny kelp and winged kelp. Although lobster continues to be Maine’s number one commercial fishery, that industry faces uncertainty as climate change forces lobsters to migrate further north in search of colder waters. Since kelp is considered a winter crop, it has the potential to provide fishermen with supplemental income during the off season.
Maine’s aquaculture regulations apply to finfish, shellfish, and marine algae. Through a tiered system, Maine has three primary avenues for establishing a seaweed farm, with key factors being size and purpose. Maine’s Department of Marine Resources (MDMR) issues a limited-purpose aquaculture license for one calendar year (with an opportunity to renew) to farms limited in size to 400 square feet; the license can take mere weeks to issue. These types of farms are required to use only certain types of gear, such as rafts with attached ropes, or longlines. For larger farms, MDMR issues either a standard or experimental lease. Experimental leases—also referred to as a limited-purpose lease—are for farms no larger than four acres focused on scientific or commercial aquaculture research and development. Such farms can operate under the experimental lease for three years, with an option to renew only available to those farms engaged in scientific research. Standard leases are for farms up to 100 acres and can be granted for a period of up to 20 years. Due to procedural requirements, standard leases (which require public notice and hearing) can take over a year to issue. Experimental leases usually take less time, but in some instances, MDMR may exercise its discretion to hold a public hearing, which leads to a longer permit process. NOAA Fisheries, State by State Summary of Seaweed Aquaculture Leasing/Permitting Requirements (2021).
Maine’s tiered permitting system allows for faster processing times for smaller or research-focused farms. Even with a tiered process, MDMR often struggles with a backlog in processing aquaculture leases, similar to Alaska. The state is attempting to address this problem through legislation that would streamline aspects of the aquatic permitting process, including creating a procedure to convert an experimental commercial lease to a standard lease if certain conditions are met.
In Maine, there are multiple resources available to start a seaweed farm. Atlantic Sea Farms, a Maine commercial seaweed farmer and producer, helps new seaweed farms by providing free seed and technical assistance, as well as buying and processing seaweed from local farms. Atlantic Sea Farms sells kelp cubes for use in baking and cooking, along with kelp powder and seaweed condiments, nationwide.
On the West Coast, California—despite its long coastline and increasing interest in aquaculture—lags behind the growth in seaweed farming experienced in Alaska and Maine. One of the largest hurdles in California is the geography of its coastline. Unlike Alaska and Maine, not much of the California coastline is conducive to seaweed farming. Another challenge is the state’s lengthy permitting process.
Similar to Maine, California’s aquaculture permitting process generally does not distinguish between fish, shellfish, and aquatic plants. Although multiple agencies are involved, there are three main steps a farmer must take to establish a seaweed farm in California’s waters: (1) obtain a state water bottom or water column lease from the California Fish and Game Commission, (2) complete an environmental review/analysis, and (3) acquire permits for farming. The entire process could take a farmer more than three years, and potentially up to a decade. An initial state lease for aquatic plants may be granted for up to 25 years, with an opportunity to renew. California’s seaweed farm permitting process is unique among other states in that a comprehensive environmental analysis, which can cost up to $500,000, is required under the California Environmental Quality Act. Sea Grant Cal., Seaweed Aquaculture (2024). This review may also require tribal consultation if the farm would impact Native tribes. See Cal. Pub. Res. Code § 21084.2 (2015).
Despite the space and permitting challenges, there are at least two seaweed farms located in California’s state waters. HSU ProvidenSea, California’s first commercial farm, is located in Humboldt Bay and is a collaboration between Humboldt State University and GreenWave (a nonprofit organization that provides support to seaweed farmers across the country). Sunken Seaweed in the Port of San Diego collaborates with researchers to assess the effects of farming on the San Diego Bay’s ecosystems. Both farms, located in ports and thereby avoiding California’s extensive permitting process, serve as test sites to provide state officials and future farmers with useful data.
Other coastal states also are exploring seaweed farming; however, many states are reluctant due to a lack of interest, questions surrounding economic feasibility, or a “not in my backyard” mentality. New York, for example, passed a bill in 2021 that permits Suffolk County to lease underwater lands ceded to it by the state for the purpose of seaweed cultivation. Shinnecock Kelp Farm, which pre-dates the 2021 legislation, is the first Indigenous-owned seaweed farm on the East Coast and uses seaweed to restore the waterway. One local company, the Montauk Seaweed Supply Company, bridges the gap between land and sea farmers by purchasing seaweed to use as fertilizer. Connecticut, Hawai’i, Massachusetts, New Hampshire, and Rhode Island are examples of other states exploring incentivizing seaweed farming through legislation.
A seaweed-focused permitting process is necessary to protect the local ecosystem, maintain a level playing field among businesses, balance competing uses in the nearshore marine environment, and ensure that sustainable farming ventures thrive. Of the three states outlined above, Maine appears to have the most streamlined permitting system, whereas California’s regulatory process is potentially overburdensome for smaller farms. That said, certain components from California’s process, such as tribal consultation, are important. Seaweed farming should have its own regulatory framework, as it is arguably the least risky of aquaculture “crops”: It requires no inputs and generally benefits the ecosystem. A key takeaway from Maine’s aquaculture permitting scheme is that the smaller-size tier helps get small farms into the industry. States should consider streamlining permits for small experimental seaweed farms, and then using information from those farms to inform future regulations, as is currently the practice in California and Maine. Those farms can then educate new farmers.
Seaweed farmers in every state face spatial planning, licensing, permitting, and other requirements from state agencies. While some states, such as Maine and Alaska, have found ways to speed up the process, an easy-to-understand permitting structure is essential. Permitting must be backed by science, based on an understanding of the local ecosystem, and designed to address potential issues. For example, seaweed farmers must be required to grow native seaweed, which states can ensure through permitting and oversight, to prevent threats to wild seaweed. Requirements may include maintaining a broad inventory of local parental stock to protect diversity and avoid extensive inbreeding, preventing monocultures vulnerable to environmental stressors. Seaweed farms can reduce the amount of light that reaches the seafloor below, so states should only permit farms located away from seagrass beds. Another issue states should aim to prevent is entanglement or disturbance of marine wildlife.
While it may seem that seaweed farmers have the entire ocean at their disposal, most sites are in public waters and, therefore, must accommodate other users such as boaters, fishermen, and shorefront property owners. Some level of environmental review is also necessary to ensure that seaweed farming can coexist in marine habitats and provide ecosystem benefits. Finding the right level of environmental review is a balancing act.
Regulators also must consider how seaweed will be used after it is grown and harvested. For example, seaweed that removes pollutants from the water column should not be consumed. Food safety regulations are required to ensure such seaweed does not reach consumers’ plates and that seaweed grown for human consumption meets baseline standards. Additionally, seaweed for consumption is processed differently than seaweed used in fertilizer or feed. State laws and federal action should account for these considerations. Lastly, states and companies must invest in processing and distribution facilities key to the survival and growth of seaweed farming. Such facilities must be located close to farms to process seaweed in a timely manner to prevent spoliation and to reduce transportation costs and carbon emissions.
One looming question to address is how seaweed farms may combat climate change, particularly on a long-term and larger scale. While research on seaweed alone showcases its important role in climate change mitigation, farmed seaweed still presents questions. Research shows that seaweed naturally sequesters carbon when it sinks to the ocean floor. However, further research is needed to understand the carbon emissions of seaweed that is harvested and processed for consumption (and not sunk). Such processing can affect its climate-fighting powers, canceling out the carbon it has absorbed, or even leaving a net positive carbon footprint, particularly when factoring in emissions from transportation bringing seaweed to market.
However, using seaweed for feed and fertilizer, where the carbon may remain captured, is an area worth further attention. Since seaweed absorbs nitrogen, using seaweed as a fertilizer or soil amendment in terrestrial agriculture enhances the photosynthesis rate of crops. This use of seaweed may bolster climate benefits while simultaneously promoting sustainable farming methods on land, creating a sea-to-soil pathway. Additionally, farmers choosing to utilize seaweed fertilizer instead of industrialized nitrogen fertilizer would go a long way in reducing the harmful chemicals entering waterways.
Despite the potential for seaweed farming to remove carbon dioxide and other harmful pollutants from the ocean, these benefits may not be fully realized if the industry grows haphazardly or is industrialized by large corporate farms. Responsible growth rooted in science is essential. States must implement a seaweed farming strategy that benefits the ecosystem and coastal communities.
To reap the benefits of seaweed cultivation, coastal states should continue to encourage and support Indigenous and smaller farms to ensure the industry grows sustainably. States should focus on incentivizing those with experience in related fields and who are already involved in the blue economy, such as lobstermen, to enter the seaweed farming industry. Additionally, grant programs could reduce cost barriers for Indigenous communities and let such communities lead the way, incorporating traditional ecological knowledge into the farming practice. Collectives formed through buyers such as Atlantic Sea Farms (Maine) and Barnacle Foods (Alaska) can guarantee a source of income for smaller farms that otherwise would not be able to compete with large commercial entities. Local nonprofit organizations also can play a role in connecting farmers with buyers and providing resources for farmers, including trainings and market development workshops, as the Native Conservancy and GreenWave have done. Additionally, states and companies can provide consumer education on the nutritional benefits of consuming seaweed, increasing demand for this superfood.
The future of seaweed farming also depends on federal action. Given the number of federal agricultural subsidies provided to terrestrial farmers, seaweed farms also deserve attention to ensure they can grow sustainably and provide net benefits. Funding should not only be considered for seaweed farms that provide seaweed as a commodity, whether fertilizer or food, but also for seaweed grown to remove excess nitrogen and phosphorous and sequester carbon. Federal agencies should evaluate the benefits and impacts of coastal seaweed farming and devise necessary metrics, best practices, and regulations, which states could then use as a common basis when developing their own permitting requirements. In 2019, Congress created the Interagency Working Group for Farming Seaweeds and Seagrasses, chaired by the U.S. Department of Agriculture in coordination with NOAA, to report on opportunities for farming seaweeds and seagrasses. Additionally, pending federal legislation would allocate funds to increase seaweed farming research, provide technical assistance, involve tribal communities, and identify best practices.
When rooted in Indigenous knowledge, with communities front and center, seaweed farming may create equitable opportunities for coastal communities battling the climate crisis, improve environmental health, and cultivate food sovereignty. Further research is needed to understand how to properly scale up seaweed farming to provide climate benefits and minimize potential adverse impacts. Government and organizational investments are also critical to support farmers, whether by improving the permitting process, providing grants, or offering training opportunities. While federal agencies should research and issue guidance on best practices, coastal states must establish criteria that ensure sustainable siting and growth of seaweed farms. Efforts to incentivize the development of processing facilities, establish food safety standards, facilitate consumer education, and make supply chain investments must be prioritized by all levels of government to ensure the success of this promising industry. Seaweed farming presents an opportunity to invest in our future and get an emerging farming practice right—by creating a sustainable, science-backed industry if we take the time to learn, grow, and adapt.
