Oyster shell recycling aimed at reducing Casco Bay acidification

Zach Gordon and Libby Davis of the Maine Coastal Program lift a barrel of oyster shells to dump into a container at ecomaine in Portland on Friday. The Casco Bay Estuary Project and Maine Coastal Program have been collecting oyster shells from Portland restaurants to reduce acidification in Maine’s oceans. Shawn Patrick Ouellette/Staff Photographer

Tucked behind some of Portland’s most-beloved restaurants, bright blue bins filled with oyster shells swarm with flies. Collecting these shells is not a glamorous job. If one lid is slightly ajar, the sharp smell of drying shells hangs in the humid summer air.

Despite the odor and flies, twice a week Zach Gordon and Libby Davis load about 20 of these 100-pound bins onto a 10-foot trailer attached to the back of Davis’s truck and haul them away.

“I’m doing it for Mother Nature,” Davis chuckled.

Since June, the team has gone out on Tuesdays and Fridays to collect discarded shells from 10 restaurants as part of Ocean to Plate to Ocean, a pilot project by the Casco Bay Estuary Partnership and Maine Coastal Program to reduce ocean acidification by reintegrating the recycled shells into Casco Bay.

The effort was prompted by a report from the Commission to Study the Effects of Coastal and Ocean Acidification on Commercially Harvested and Grown Species, established by the Maine Legislature in 2014. It recommended spreading shells or other forms of calcium carbonate to remediate the impacts of local acidification, a result of climate change.

In its final report published in 2015, the commission highlighted the connection between ocean acidification and rising carbon dioxide levels in the atmosphere. The report noted that ocean acidification has increased 30 percent since fossil fuels were first used.

Maine’s effort to recycle oyster shells is not novel; nearly 20 other states have shell recycling programs. However, most states do not recycle shells to reduce ocean acidification; instead, they use the shells to restore natural oyster reefs.

The report cites research by Mark Green, professor of natural sciences at Saint Joesph’s College, finding that acidification hinders calcification, the process by which lobsters, crabs, mussels, oysters and clams form shells. The goal of shell recycling is to add natural calcium sources to the water to reduce acidity and promote calcification.

The Casco Bay Estuary Partnership received $99,180 in funding for the project through Climate Ready Estuaries – an EPA program linked to the National Estuaries Program. Project partners include the Maine Coastal Program, which is running the shell collection effort; Gateways to Opportunity, which is conducting outreach for youth engagement programs; and Bigelow Labs, which is researching the use of shells to ameliorate the impacts of acidification on shellfish aquaculture.

Gordon, a graduate student participating in the University of New England North’s ocean food science program, and Davis, the general manager at Maine Oyster Company, are the program’s two collectors.

Gordon and Theresa Torrent, coastal educator and communications coordinator at the Maine Coastal Program, reached out to about 15 restaurants in Portland. Ten agreed to participate in the pilot program.

Davis, who joined the project after hearing about it through the owner of Maine Oyster Company, has a bachelor’s degree in biology and a truck that tows the 10-foot trailer loaded with shells.

On collection day, Gordon, 26, and Davis, 27, hitch the trailer at 8:30 a.m. From there, the team goes from restaurant to restaurant collecting anywhere from a single, 6-gallon bucket filled with oyster shells to seven 30-gallon bins. In place of the full containers, the two leave clean ones and then drive to ecomaine in South Portland for the most taxing aspect of the job – dumping the shells.

The team learned that each bin must be dumped by two people after Gordon hurt his back dumping one by himself. The shells are dumped into two 30-cubic-yard rolloff containers that are covered to prevent seagulls from getting into the shells. The containers will sit at ecomaine for a year after the last shells are added so the shells can “cure” to ensure all bacteria is dead.

The year-long curing process complies with Department of Environmental Protection rules. It also alleviates concerns about introducing non-native bacteria, as many of the oysters consumed in Maine come from outside the state. The cured shells will then be ready to be dumped in the bay. The team is still developing a method for the restoration.

As with any pilot program, the team has had to troubleshoot obstacles, such as Gordon’s back injury and driving a 10-foot trailer through the Old Port. They have also gotten help through community partners. The restaurants’ efforts to throughly sort shells and ecomaine’s help creating a truck ramp have made the job more efficient.

Kate Lusignan, Central Maine, 5 August 2019. Article.

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