How Seaweed Farming Can Breathe New Life into Ocean Dead Zones

Picture a farm that requires no freshwater, fertilizers, pesticides, or feed; the crops grow rapidly, and, as a bonus, these crops clean the ocean. 

“Our crops require zero input to grow,” says Bren Smith, executive director of Greenwave, a sustainable seaweed and shellfish company that, through its farming practices, sequesters carbon and rebuilds reef ecosystems.

Smith calls himself a 3D farmer because of the way he grows his crops of giant kelp. It’s an underwater form of vertical farming grown on longlines suspended between four and eight feet below the surface of the water. Smith plants giant kelp, which he says is “just eating what’s in the water. We love kelp because of how fast it grows.”

Kelp spores appear in September. “In the leaves you’ll see these chocolate stripes and that means the kelp is reproductive,” he says. “It grows slowly the first 2 months. Then by January, it grows fast. The leaves are up to 15 feet long by the time we harvest them.”

An ocean dead zone the size of New Jersey

Factory farming is a dirty business. It’s responsible for ⅓ of global greenhouse gas emissions and is fully dependent on oil for transport. Plus, pesticides and fertilizers used on factory farms are derived from petrochemicals and runoff from these chemicals often winds up in our waters.

“Whereas seaweed farms clean the oceans,” says Brandon Barney, co-founder and director of research and communications at Primary Ocean, a public benefit corporation created to reverse climate change through seaweed cultivation and commercialization. “Seaweed does this by absorbing nitrogen, phosphorus, and carbon dioxide.”

“Too much nitrogen and phosphorus, which come from stormwater runoff, fertilizers used in factory farming, sewage, and automobile and industrial emissions, cause dead zones in the ocean,” Barney says. “A dead zone is an area with low oxygen levels. And no organisms can live in a dead zone.”

Researchers at UC Santa Barbara found that over 800 watersheds from 32 states deliver fertilizer runoff to the Gulf of Mexico, leading to unwanted algal growth and an expanding dead zone that threatens the health of large swaths of ocean ecosystem. According to the UC Santa Barbara scientists, this Gulf of Mexico dead zone was 18,000 square kilometers, roughly the size of New Jersey, as of 2019. By producing oxygen, and absorbing an excess of nutrients, seaweed farms can literally help breathe new life into ocean dead zones.

In addition to absorbing excess nutrients, seaweed also acts as a sponge for heavy metals like cadmium and copper.

Replacing plastic with seaweed

Seaweed can replace plastic. Of the more than 300 million tons of plastic produced every year, 8 million tons wind up in our oceans.

Many fish and other sea creatures eat plastic, which is harmful. In fact, ocean plastics contribute to dead zones.

Instead of contributing to the staggering mountain of plastic waste, companies are turning seaweed into biodegradable “plastic” products. The benefits are broad because these seaweed “plastics” decompose when reintroduced back into the ocean. 

Some companies have introduced biodegradable dinnerware, seaweed-based packaging, water pouches instead of plastic water bottles, and cups made out of seaweed that you can eat. “When you look at how traditional products, such as how plastics are produced, and then you look at how products made with seaweed are manufactured the benefits are huge when we switch to seaweed,” Barney says. “The same goes for waste from traditional products. Products made with seaweed are good for the planet.”

Seaweed as biofuel

Some scientists are turning kelp into biofuel. One scientist at Norwegian University of Science and Technology’s Department of Energy and Process Engineering published a study on how to turn sugar kelp into oil.
“Think corn-based ethanol,” Barney says. “It’s been done. Now, seaweed could be turned into biofuel and unlike corn, which takes a lot of land, fertilizers, pesticides, and fresh water, seaweed doesn’t need any of those resources.”

Seaweed to power our cars is still in the experimental stage, but anything we can use to reduce the use of fertilizer and pesticides is a net positive for the health of our oceans.

Multiple health benefits 

If you eat sushi, you’ve eaten seaweed. You’ll also find seaweed in salsas, sauces, salads, seasonings, and nonfood items; it’s in cosmetics, pharmaceuticals, as a thickener in some ice creams, animal feed, and fertilizer. A report in the journal, Advancement of Food and Nutrition Sciences, found numerous health benefits from eating seaweed; it’s a good source of dietary fiber, omega 3 fatty acids, essential amino acids, and vitamins A, B, C, and E. 

Seaweed farming is international

Seaweed farming is not new. Japanese fishermen farmed seaweed as early 1670. When Captain James Cook visited Tonga in the late 1700s, the natives advised him to eat seaweed to restore his health. Many locals believed this powerful sea vegetable provided longevity and vigor. 

Today seaweed farming is a big industry in China, Korea, and even Ireland. It’s also a major business in the Philippines, Norway, Indonesia, Malaysia, and Zanzibar. Here in the U.S. you can find dozens of seaweed farms in New England, the Pacific Northwest, and Alaska. According to the National Oceanic and Atmospheric Administration (NOAA), seaweed farming is the fastest-growing aquaculture sector. In Alaska, home of the largest kelp farm in North America, there was a 200 percent increase of product from 2017 to 2019. 

“We’re looking for sustainable solutions and seaweed happens to have a lot of strong sustainability characteristics,” Scotty Schmidt, chief executive officer and cofounder of Primary Ocean, says. “Seventy percent of our planet is ocean so we’re talking about an order of magnitude larger than traditional agriculture.”

“Our seaweed, giant kelp, has many uses, as food, feed, fuel, nutraceuticals, and more, but Primary Ocean is focused on fertilizers, specifically, a new class of crop input defined in the 2018 U.S. Farm Bill as biostimulants.” (Some advertisements label biostimulants as “probiotics for plants.” They enhance the heath of plants.) 

An alternative to synthetic fertilizers

“Seaweed is high in micronutrients and phytohormones,” Barney explains. “Phytohormones are plant hormones that help plants grow. Using seaweed as a fertilizer replaces the need for using chemical-based fertilizers. Overall it’s better for our crops, the soil, and the planet.” 

It can also help reverse the ocean dead zones plaguing aquatic life by reducing the runoff that throws entire ocean ecosystems out of balance.

12 Fun facts about seaweed

1. When kelp decomposes, it sinks to the ocean floor and provides a tasty meal to sea creatures.
2. Sea Otters wrap themselves in kelp while they sleep to keep from floating away. 
3. On average giant kelp grows to 100 feet. Some have grown up to 175 feet in length.
4. Seaweed works 14 percent faster than trees in tropical rainforests in restoring oxygen to our oceans.
5. Kelp forests exist underwater.
6. Nature is amazing; the Kelp Fly, found on numerous beaches, helps remove rotting seaweed by dining on it.  
7. Seaweed is one of the fastest growing organisms in the world.
8. Seaweed needs sunlight to grow. 
9. Seaweed is not a plant. It’s algae. 
10. Seaweed comes in red, green, and brown colors. 
11. There are 1,000s of different types of seaweed. 
12. A few clothing manufacturers are creating textiles from seaweed.