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Shellfish Recruitment: Oyster Shell Recycling

Written on: December 8th, 2021 in Wetland Restorations

By Sarah Bouboulis, Partnership for the Delaware Estuary

The Partnership for the Delaware Estuary (PDE) has been interested in living shorelines and shellfish research since the early 2000’s, led by Senior Science Director, Dr. Danielle Kreeger. Since 2004 PDE has installed several living shorelines throughout the Delaware Estuary, primarily using materials such as coconut coir logs, Oyster Castles© and oyster shell bags. During the formative years of PDE’s Delaware Living Shoreline Initiative program (DELSI) and subsequent project monitoring, it became clear that oyster shell bags, in many instances, were one of the best choices for living shorelines based on shellfish recruitment and shoreline stabilization data. However, recycled oyster shell were becoming a hot commodity (i.e. expensive and hard to come by). Subsequently, PDE saw a need for an oyster shell recycling program within the Delaware Estuary.

It took quite a few years to have resources lined up in such a way that both space and funding, for management of the shell, were secure. The stars finally aligned in 2016 when space and funding became available simultaneously in Wilmington, Delaware.

Pre-pandemic, the program was collecting from 9 restaurants in Northern Delaware and one in Dover, Delaware. Between 2016 and 2019, the restaurant collections averaged 1,400 bushels a year (or 70,000lbs). Sadly during 2020 most restaurants closed for an extended period of time and, unfortunately, a few restaurants were forced to close permanently. Since businesses have begun to open back-up, collections have re-started and for 2021 the total collections will near 1,000 bushels.

Currently, collections are only with restaurant partners. Pick-ups are conducted weekly or bi-weekly, depending on the season, and the shell is brought back to the shell management area in Wilmington. Shell is cured in the open between 6-12 months, being turned at least once during that time before it is then, usually, bagged and ready for use on living shoreline or other restoration projects. The curing time is set to make sure the shell has properly cured and there is no risk of introducing disease, pathogens, or other foreign materials back into area waters.

Two large shell piles.The right pile is shell that has been cured for 6-12 months. The pile on the left is fresher shell in the curing process.

The next step is preparing the shells for transport and/or use on a living shoreline. This typically involves putting the shells into mesh bags. This is the most time and labor intensive portion of the process and it would not get done without the help of countless volunteers. It is also a group activity, needing around 10 volunteers per bagging session. Groups from University of Delaware, Delaware Technical Community College, Wilmington Green Jobs, Bank of America, the Camden Power Corps and many others have all helped with shell bagging. And PDE is so appreciative of their participation!

The fully cured shell goes primarily to living shorelines projects, many put in by PDE. Recycled shell is also sold to restoration partners for other projects such as reef creation and aquaculture research, as well as living shorelines being implemented by others. The main focus of PDE’s oyster shell recycling has always been to support projects within the Delaware Estuary, however, when excess shell exists it has been sold outside the Estuary. You can view a new story map outlining all of PDE’s living shoreline projects, most of which incorporate recycled oyster shell here.

Since inception, over 12,800 bags of shell have been created, which could secure over 4000 feet of shoreline! The shell has gone to support projects in all three states in the Estuary involving a tremendous amount of partners including the Philadelphia Water Department, DNREC, USFWS, The Nature Conservancy, Haskin Shellfish Research Laboratory, and University of Delaware, to name just a few!

Oyster shell bags being used as part of living shoreline installation in Delaware.

In 2022, PDE hopes to expand oyster shell recycling into the city of Philadelphia along with help and support from the Philadelphia Water Department. In such a major metropolitan area, and with a much larger shell management area, the program should be able to collect and cure several times more oyster shell than our current operations.

To learn more about the program, how to volunteer or to purchase shell, you can view our website here or contact Sarah Bouboulis;

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