Bivalve shells reuse and recovery: bio-inertisation and engineering applications.

The disposal of waste material constituted by shells resulting from processing subsequent to Bivalve Molluscs harvesting for sale purpose constitutes a big problem for the Venice Lagoon ecosystem from the environmental point of view both because of the large volumes involved and its specific characteristics. In some areas this material, which is currently discarded at sea, comes up to cover the lagoon bed with a thick layer that prevents the benthic communities natural development. A previous work highlighted that as shells are bio-minerals constituting the exoskeleton of organisms known for their ability to accumulate pollutants, they are able to block these pollutants in the crystal structure of the valve thus acting as bio-inerting tools. So we assessed the possibility of a differing shell waste management studying the opportunity to use it in the construction of protective barriers for hydraulic consolidation such as gabions. This would offer the double advantage, on one hand, to provide a sustainable solution to the shell waste disposal problem, with the aim of an integrated closed-loop (the material produced in the lagoon of Venice will be reused in the same place), and, secondly, to remove inert material that contains pollutants that would, in this way, subtracted from the system. After the product implementation we evaluated the evolution of its biological and mechanical characteristics with the aim of highlighting its stability, strength and effectiveness, as well as the opportunity to extend the use of this technology in all erosion risk areas located in the Venice Lagoon and, in general, throughout the Northern Adriatic.