From seaweed to soil: South Florida beach town finds a solution to a stinky problem

Piles of brown sargassum seaweed line the shores of Florida beaches and while it isn't harmful, the rotting smell drives beachgoers away.

Since 2011, sargassum seaweed has been showing up almost seasonally along beaches, with 2015 and 2018 being record years for accumulation. This year, large amounts of seaweed have washed ashore in South Florida.

After a while, the leafy brown marine plant emits a pungent odor. Ocean scientist Dr. Tracy Fanara explains that when the seaweed decomposes, it releases sulfur dioxide, which smells like rotten eggs.

The gas emitted can be unpleasant for human visitors irritating your eyes, nose and throat. The decomposition can also bring more nutrients into the coastal waterways, causing more harmful algae blooms.


"It's essential for crabs, eels, fish like amberjack that we actually really depend on in the United States. These patches of sargassum are extremely important for the ecosystem," Fanara said. "However, just like anything else, in large quantities, they can wreak havoc and which they are doing on our shorelines."

Researchers with the University of South Florida Optical Oceanography Lab have been tracking sargassum movement in the currents using NASA and NOAA satellites since 2011.

"The total amount of sargassum in the Atlantic Ocean is a record high," University of South Florida Professor Chuanmin Hu said.

Hu and his research students recently gathered sargassum samples in the Gulf of Mexico, where large amounts surrounded their ship.

It's possible this year could be a record for sargassum, but Hu said his team won't know that until later this summer.

"This year is bad, and it's likely to continue to grow by end of June or July," Hu said. "We still have a huge amount of sargassum in the Gulf of Mexico and the Caribbean Sea, and that situation will not go away until at least several months later."

The solution: From smelly seaweed to soil rich in nutrients

The city of Fort Lauderdale is taking this smelly problem on its beaches and repurposing it, composting the seaweed and using it as soil. About 70 to 80% of the seaweed is taken away by truck along four miles of the beach. 

Fort Lauderdale Superintendent of Parks Mark Almy showed FOX Weather's Brandy Campbell how the composting process works. After it's dumped out of the truck, the seaweed sits for 120 days.

"It is laid here, spread out by a tractor, and then it's spread over the top with dirt and some remaining seaweed where it will sit," Almy said. "And out of this, you'll see at the very end of this project, where it's totally processed, we get one yard for every ten that we put in."

Almy said it's free dirt for the city, and plants grow "like crazy" in it.

After the composting process is complete, the soil is used for planting in parks and along major boulevards in Fort Lauderdale.

Before composting, the city paid about $250,000 a year to send the seaweed to a landfill.

More seaweed solutions

While Fort Lauderdale has the only registered sargassum composting facility in the state, the Florida Department of Environmental Protection has been working with municipalities throughout Florida to identify the best way to manage sargassum on their beaches using different methods.

A Florida DEP spokesperson gave a few examples of creative ways communities deal with sargassum. 

A tree farm in Homestead, Florida, accepts and composts some sargassum seaweed, but this is considered standard farming practice and does not require a permit. 

Some beaches integrate some seaweed into the beach, and the seaweed left over is then disposed of at permitted landfills or a composting facility.

The Village of Key Biscayne is also looking into alternative seaweed or composting for sargassum but needs a location for composting. Until then, it has been transporting the seaweed to a permitted landfill in Miami.

In the meantime, the DEP proposes to define sargassum in the state Organics Recycling Rule and add it as feedstock for composting, which will mean more options for disposal.