Concrete for Coral Reefs – Regenerative Sustainability

In honor of the First International Conference on Concrete Sustainability, taking place in Tokyo this coming May, I thought I would present a post on the opportunity for concrete in a regenerative sustainability capacity.  Rather than focusing on doing less harm, I wondered if there were opportunities for concrete to repair harm done, and contribute to the restoration of our resources.

 

There seems to be an opportunity for concrete in the restoration of coral reefs.  Coral reefs have been damaged by human contact from destructive fishing practices, off-shore industry platforms, and even the very divers who are admiring the reefs.  Their growth is further thwarted by pollution from drainage water and oceanic temperature shifts from climate change.  The economic impact is not only the loss of marine biodiversity, fish stocks and  the local communities who rely on fishing for food and their livelihoods, but also the protection from storm waves.  Despite the quantifiable damage, the responsibility for both protection and conservation is not directly correlated, as reefs are open commons, and thus lacking clear ownership.   This problem of market based strategies for linking climate concerns with economic stakeholders is a recurring and increasingly critical theme that is worth noting and will be taken up in later postings.  Today, we will deal with the technology of reef restoration, and the contributions of the concrete industry.

The goal is the restoration of reefs, with both the objective of providing habitat for marine life and protection for the coastal areas.   This is not to be confused with dikes or concrete breaks, which may also provide the role of protecting the land from the rising ocean levels, such as in Holland.    While the principal function of the artificial reef materials is structural, not just any material will do.  For example, some of the original approaches of sinking old ships or other large equipment which had reached the end of its useful life runs the risk of introducing pollutants or materials that can disrupt the chemistry of the surrounding waters.   From this perspective, concrete has emerged as an ideal material, not only for making the framework strong and resistant to the elements, but also due to its low acidity which favors accelerated coral growth.     

Often the immediate concern is for protection from storm surges, and past solutions have been to create a physical barrier, such as a sea wall.   These have been made of rock, sunken ships, or any heavy material, and are effective in breaking the waves.   However, they don’t provide much of a substrate to encourage a biological restoration.  This was the approach taken by Wayfarer Environmental Technologies, who developed the Oysterbreak system, precast concrete rings, measuring 5 feet in diameter which link and stack to create an engineered base for the restoration of an ecosystem.    Wayfarer provides the molds for the precast rings, and a proprietary organic mix for the “Oystercrete” to encourage the oysters to attach to the ring. The rings can be poured on site, positioned in the water using an airboat with a crane boom or barges.   Both the design of the interlocking rings and the weight of the precast help keep the rings in place.  The hollow rings use less material, reducing the initial cost of manufacture and placement, but “grows” additional material through the accumulation of oysters and other biological matter, thus improving in value over time.

On a smaller scale, the Reef Balls are also made of precast concrete, but are more directed toward the restoration of coral reef because they mimic the limestone boulders to which the organisms attach.  The Reef Ball Foundation has been developed as a non-profit to rehabilitate marine reefs around the world, and has made its technology scalable to work with any sized project. Concrete has also been especially well suited to provide the “potting material” for coral “nurseries,” where coral is harvested and then transplanted to other areas.   However, make no mistake.  There is no quick fix to restoring coral reefs.  It can only be grown and propagated through the painstaking efforts of hundreds of “gardeners.”     But in this effort, concrete is part of the regenerative solution.