Oysters are a salty and sweet delicacy (if you chew them). But after you're done slurping them down, what do you do with the shells?

Conservationists have an idea; they're using them to help build oyster reefs in New York Harbor, and those reefs could end up doing multiple jobs, including keeping the city safe from hurricane waves.

Castoffs to save the day

The idea to reuse the oyster shells came about in 2014 with the Billion Oyster Project. The goal of the initiative is to restore oyster reefs along New York Harbor, reefs that were once a vital part of the marine life ecosystem but collapsed due to overfishing and pollution. Until the Clean Water Act of 1972 started cleaning up the harbor, oysters simply couldn't survive. Now they can do their part to help the harbor thrive. In fact, Matt Hickman wrote about this group in 2016, when they crushed up 5,000 commodes to bolster the oyster population. They are old hands at doing right by oysters.

Here's how the process works, as reported by NPR.

New York seafood restaurants collect discarded oyster shells and place them in blue bins that are picked up by a Billon Oyster Project partner, the Lobster Palace, a seafood supplier, five days a week. The shells are transported to Brooklyn, and once a month, these shells are brought to Governors Island, where they will be placed to withstand the elements for a year, "curing" them of any contamination.

Oysters topped with bacon and cream fraiche These oysters have several 'lives' — one as an appetizer and another to clean up the harbor. (Photo: Noodles and Beef/Flickr)

After a year, they receive one more cleaning and are moved to the Urban Assembly New York Harbor School. The school offers technical and vocational training in marine sciences, and it's there that the magic really happens. In classrooms equipped with oyster hatcheries that mimic a springtime environment, students grow oyster larvae. These larvae each grow "feet," limbs covered in a sticky substance. These student-grown larvae are moved to a tank with the restaurant shells where it's hoped that the larvae's "feet" will attach themselves to the shells. If successful, the shells can house 10 to 20 new oysters, depending on the shells.

"It's remarkable," Madeline Wachtel, Billion Oyster Project's director of Strategic Projects, told NPR. "Using the calcium carbonate in the water, oysters build their own shells."

Now, oyster lovers are probably thinking, "Oh, my, yes. Bring me those oysters." But these oysters aren't for eating. Provided the waters of New York Harbor are warm enough, they are placed in a cage or a shellfish bag and placed in the harbor. The structures provide a stable area for the oysters to join together and start saving the harbor.

An immediate impact

Oysters, obviously, aren't very large, so cleaning up the harbor seems like a daunting task. The oysters, however, do it with aplomb. According to NPR, an individual oyster is capable of cleaning 30 to 50 gallons of water a day, so when you put large groups of them together, there's a lot of cleaning going on in the harbor. In addition to their filtration services, oysters provide food and shelter for a variety of marine life.

Since 2014, the Billion Oyster Project has created 28 million new oysters, explaining that the presence of these oysters has made the harbor better than it has been in 150 years.

"We definitely noticed an improvement when we put oysters down on the bottom," Katie Mosher, restoration manager of the Billion Oyster Project, told Agence France-Pressegenc. "There's more fish, more crabs. And it happens right away."

In addition to cleaning up the water, the oyster reefs serve as natural breakwaters, structures that protect coasts and harbors from the force of the ocean's waves. New York is keen on the idea as hurricane waves can wreak havoc on the city's infrastructure. The state's Office of Storm Recovery has partnered with the Billion Oyster Project to install oysters on its Living Breakwaters Project, a project intended to reduce and prevent the erosion of Raritan Bay caused by storm waves.

Benefits to more than just the harbor

Billion Oyster Project volunteers ready bags of oysters for placement in the harbor The placed oysters can make a significant contribution to the health of the harbor. (Photo: Don Emmert/AFP/Getty Images)

The Billion Oyster Project helps more than just the waters of New York Harbor, however.

For businesses, the project is a way to reduce trash while engaging in a sustainability project that gives back to the environment.

For Brian Owners, the owner of Crave Fishbar, it's a win-win. The restaurant goes through about 20,000 oysters a week, and he estimates that Crave Fishbar has donated about 20 tons of shells to the project in only three years. "We want to minimize our waste and increase our impact on the community," he told NPR. "Working with Billion Oyster Project is an obvious fit."

For the executive director of the project, Pete Malinowski, the real benefit is to the students who participate in the initiative. Malinowski began developing the project in 2008 with the goal of teaching students how to apply what they learned in the classroom to the harbor. Today, the Billion Oyster Project has programs in more than 80 middle and high schools, working with oyster research stations that have been set up around the harbor.

"On any given school day, there are several middle school classes at the water's edge, measuring oysters and conducting research," Malinowski told NPR. "Through this work, students develop awareness and affinity for the resource and the confidence that comes from knowing their actions can make a difference. With young people who care, the harbor has a real fighting chance."

Used oyster shells are saving New York Harbor
The Billion Oyster Project collects used restaurant oyster shells and uses them to build oyster reefs to shore up New York harbors.