Benefi-shell Recycling

Jayne Merner Senecal roots through a buzzing pile of rich brown compost to pluck out one of the most powerful components in the mix—a clam shell, with the slick sheen of viscera and a vein of green sand.

Shells, a natural marine byproduct that ends up on land as waste, find a second life underfoot and on the wall. For 30 years, the Merner family has been using clam, oyster, and mussel shells, along with smaller amounts of seaweed and fish scurry, to boost the nutritive value of its Earth Care Farm compost.

The written historical record of using shells and other marine waste to amend soil is silent, but many researchers have established the connection between shell waste and healthy soil. For example, in 1847 Canadian geologist Abraham Gesner suggested that compost could be made of prehistoric shell middens (trash piles) burned, ground up, and mixed with peat. More recently, a 2014 study by scientists at Smithsonian Environmental Research Center, published in Landscape Ecology, documented “the legacy of ancient human practices” and its effect on “modern ecosystems.”

The archaeologists unearthed 3,000-year-old shell middens in the Chesapeake Bay area that promoted diversity among native plant species, helping them survive and thrive. Soils eventually created by these compost-ing middens had nearly 45 times more calcium and 6.7 times more nitrate than soil samples taken elsewhere.

Today, few landfills will accept fresh shell waste, says Senecal. “It’s smelly and wet, and it’s too hard for them to handle—but we are really good at it.”

Twice a week, shellfish processors dump up to 30 metric tons of mussel and clam waste at Earth Care Farm’s Charlestown facility. Earth Care workers immediately scoop it into carbon bowls created within an active compost pile and cover it with more brown materials such as leaves, straw, and wood chips. Then, workers fully incorporate the wet mixture. The whole process only takes about an hour, and even on a stifling hot day, there is little odor from a recent delivery. The shells take a year to break down, and the larger pieces are screened out of Earth Care’s finished product.

(Above) A 70-by-15-foot of thousands of oyster shells stacked in a grid of gabion cages adds a new dimension to the Island Creek Oyster Bay in Boston. Photograph by Michael Piazza.

“The shells are full of micronutrients that are hard to come by from land re-sources—a wonderful source of calcium. The traditional Rhode Island soil has a low pH of 5. Our shells, as they break down, release lime and naturally increase the pH to get to the neutral 7 that most garden plants thrive on” she adds. “We are lucky to get it by the truck-full.”

Landscape materials suppliers also sell crushed shells as mulch and driveway cover.

Carpenter’s Farm in South Kings-town has long been a source for local beach houses. “We sell hundreds and hundreds of yards of shells—sometimes up to 80 yards in a week,” says Carpenter’s Farm’s Meg McCallig. “People like them because they go with their beach vibe.”

In Boston, the humble oyster shell has been elevated to an art piece of enormous presence. Patrons of Island Creek Oyster Bar on Commonwealth Avenue may perceive the 70-by-15-foot wall of white ridges as some trick of stucco, but closer inspection reveals that the effect is created by thousands of oyster shells stacked in a grid of gabion cages.

The sculpture began as an idea from the restaurant’s architect to decorate a blank expanse enclosing a staircase. Shore Gregory, a co-founder of Island Creek, says they misunderstood the architect’s vision at first, “We thought, OK, we’ll glue some oyster shells to the wall. We couldn’t have been more wrong.”

Instead, they launched a months-long campaign to collect the shucked oyster shells and truck them back to their Duxbury, Massachusetts, oyster farm where they were cleaned and sterilized. The wall had to be reinforced to hold the weight of 37 two-by-four-foot steel mesh cages freighted with oyster shells.

“That sense of discovery is powerful and so fun—[customers] may not understand until they are right in front of it and they see all those oyster shells,” he says. “People are really intrigued by it, and it really is a great representation of the products and the farm. We wanted people to have our interpretation of the experience of an oyster bar, and that wall is one piece of that.”

by Ellen Liberman

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