Why Blue Carbon & Ocean Farming Are Vital to the Regenerative Agriculture Movement

Photo of seaweed by Silas Baisch on Unsplash

Executive Summary

When we think of sustainability and carbon emissions, we often think of land-based issues and mitigation strategies. But the oceans, which cover over 70% of the Earth’s surface and produce an estimated 50-80% of Earth’s oxygen according to NOAA, are often overlooked in climate change and carbon mitigation strategies. The term Blue carbon refers to the carbon captured by the world’s oceans and coastal ecosystems. The size of the oceans allows them to sequester large amounts of carbon efficiently; a report in 2011 calculated that 26 percent of all the carbon released as CO2 from fossil fuel burning, cement manufacture, and farming over a decade (2002-2011) was absorbed by the oceans. But the exponential rate at which we are generating carbon emissions and destroying marine habitats is causing the natural process to fall short. Ocean farming may provide a way to enhance the ocean’s natural carbon cycle, regenerate marine habitats and address this shortage.

Ocean farming refers to the breeding, rearing, and harvesting of aquatic plants and shellfish. Ocean farms produce seaweed/macro-algae, oysters, clams, mussels, and other stationary marine species. These farms tend to be more productive than their land-based counterparts in both carbon sequestration and food production. For instance, a single acre of ocean can produce 25 tons of greens and 250,000 shellfish in five months; for context, a network of small underwater farms totaling the size of Washington state could feed the planet.

What is regenerative agriculture? How can ocean farming be regenerative?

While Regenerative agriculture has no formal definition, the term is often used to describe land-based agricultural practices aimed at promoting soil health by restoring the soil’s organic carbon. Practices classified under regenerative agriculture include no-till agriculture, where farmers avoid plowing soil and instead drill seeds into the soil and use of cover crops, which are plants grown to cover the soil after farmers harvest the main crop.

Regenerative ocean farming is a framework pioneered by Greenwave, a non-profit focused on ocean farming, which leverages a concept called 3D farming (think vertical farming but in the ocean). Regenerative ocean farms grow seaweed and shellfish (oysters, mussels, clams) in many small coastal underwater gardens of a few acres each. This form of farming is low maintenance because seaweed and shellfish don’t require additional feed beyond sunlight and the nutrients already present in the seawater. Ocean farms do not require fresh water, deforestation or fertilizers; in the process, they improve water quality and create habitats for other species.

3D ocean farming model Photo by GreenWave

A study published in the Marine Pollution Bulletin shows that commercial seaweed aquaculture has very few negative environmental effects and can significantly improve the area’s bio-diversity. Once kelp becomes established, it forms the basis of an ecosystem by providing habitat for forage fish who will feed off plankton, game fish who eat these forage fish, and so on, up the food chain to tuna and sharks, turning what was once an ocean dessert to a productive and thriving ecosystem. Thus, regenerative ocean farming requires zero inputs such as fertilizers or fresh water while promoting bio-diversity by design through underwater vertical farms.

Regenerative ocean farming provides a blue carbon win for USA

The US coastline is ideal for ocean farming and blue carbon sequestration; farming seaweed in just 3.8% of the federal waters off the California coast could neutralize emissions from the state’s $50 billion agriculture industry (34.4 million tonnes of CO2eq annually), according to a paper published in the journal Current Biology. Kelp can grow over one foot (30 centimeters) a day and help locally reduce ocean acidification.

Additionally, seaweed also soaks up nitrogen, one of the two main pollutants lingering in ocean shores. It is well known that carbon released by cars, trucks, factories and power plants is entering the ocean and turning waters more acidic. But nitrogen fertilizer used on farms also makes its way into rivers and then to the ocean, creating dead zones. The number one problem in coastal zones of the U.S. is that there is a large quantity of [nitrogen-rich] nutrients in the water, from agricultural runoff and point-source pollution from facilities like sewage treatment plants. These nutrients cause blooms of phytoplankton that decompose at the ocean’s bottom, depleting coastal waters of the oxygen needed to support life. It is a process that can result in massive dead zones, like the one located at the outflow of the Mississippi River into the Gulf of Mexico, which is currently larger than the states of Connecticut and Rhode Island combined. Shellfish like oysters and fast-growing seaweeds like kelp can extract large quantities of nutrients and nitrogen out of the ocean through a process called bioremediation. If ocean farmers devoted a little less than 5% of U.S. waters to growing seaweed, they could clean up an estimated 135 million tons of carbon and 10 million tons of nitrogen, according to a report by the World Bank.

Seaweed has a range of applications beyond carbon sequestration

However, despite a long coastline suitable for seaweed cultivation and historic kelp forests (California coast) that were lost to climate change, the U.S. has almost no offshore aquaculture operations. China and other Asian nations that produce most of the world’s farmed seaweed are expected to take the lead in establishing macro-algae as a source of blue carbon.

Indian ocean’s unique opportunity for ocean farming & women empowerment

Agriculture is central to India’s economy, with 60% of land used for agriculture. But most of the country’s cultivable land is being lost to soil degradation at an alarming rate - water erosion is responsible for more than a third of this loss. Ocean farming offers a low cost & sustainable alternative to the land-based agricultural practices that have been putting an increasing amount of pressure on the country’s arable land and can help supplement the land-based food production for a nation that has a growing population to feed.

Researchers in India have long been proposing seaweed cultivation as a form of sustainable agriculture because most of the country’s coast is ideal for seaweed cultivation with suitable tropical weather, shallow waters and a rich supply of nutrients. The regions of Gujarat and Tamil Nadu have the highest seaweed biodiversity in the country, with around 282 species being reported along Tamil Nadu’s 1,000km (621 miles) coastline alone.

Seaweed cultivation also has the potential to have a positive socio-economic impact on the coastal communities in India, particularly among women seaweed farmers, helping them increase their economic independence by providing a supplemental source of income according to this report. But as of now only a few companies are capitalizing on this opportunity; AquAgri, formed in July 2008, through a takeover of the sea plant business from PepsiCo India, being one of them. The firm has 18 seaweed cultivation sites in Tamil Nadu, providing jobs to 650 coastal residents, predominantly women. Thus, India has the opportunity to use regenerative ocean farming to not just sequester carbon and feed its growing population, but also to create an industry that empowers women in coastal communities across the nation.


There are of course certain challenges with ocean farming that need to be addressed in order for it to become mainstream.

Growing conditions: Kelp forests grow best in nutrient-rich, clear waters whose temperatures are between 42–72 degrees F (5–20 degrees C). Like plants, seaweed/kelp depend on sunlight to create energy ,and thus require constant sunshine. The ideal growth conditions occur in geographic areas of upwelling and where the waters are high in nutrients such as nitrogen. Additionally, the salinity of sea water should be about 35% to achieve maximum growth.

Digital Tools for site identification: To identify sites with the right growing conditions for sustainable ocean farming we need digital tools that allow us to not just identify the sites but also monitor the growth of seaweeds in the ocean farms using a combination of satellite imaging and on-site sensors. Finally, we need applications that aggregate the data and provide insights for the farmers to make economically and environmentally viable decisions.

Cost: As per MSE (Maine seaweed exchange), the cost of gear for a 20-acre seaweed farm is roughly $50,000. Providing farmers with cheap/easy access to capital to fund their operations is a vital challenge that needs to solved.

Demand: The key to developing any new industry is not just producing enough supply but also generating enough demand to ensure long term business viability. Thus, ensuring seaweed processing units have enough demand channels to fully utilize the seaweed and create a circular economy around ocean farming is a key challenge.


As land based regenerative agriculture and carbon sequestration practices become the standard for carbon removal, ocean farming has the potential to provide a near zero input way to feed a growing population and act as a large scale carbon sink. Thus, both land and ocean farming are vital to the future of regenerative agriculture and carbon removal strategies.

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