Waste from clam harvesting: a resource for environmental engineering in the Venice lagoon.

Clams harvesting has been widespread in the Venice lagoon since Ruditapes philippinarum introduction in 1983. Operations involved in this kind of activity include a sieving phase: operators pick out clams of commercial interest by using manual or mechanical tools. During this phase they obtain a waste that is usually discarded in lagoon. The Institution responsible of fisheries resources supervision in the Venice lagoon highlighted a management problem related to this kind of waste, that is mostly composed by shells, wood, sediment and different kind of inert materials: in the long term it can accumulate in specific areas covering the seabed and leading to an ecological quality decrease and, consequently, to a lower productivity. So it is necessary to define a strategy in order to collect this material and to avoid the need for its disposal: we took into account the possibility to use it as a filler, in total or partial replacement of the material currently used, for manufactured devices such as gabions and submerged barriers to be used for banks protection and consolidation in the Venice lagoon as well as for beaches protection from erosion. In order to do this, we worked in two directions: on the one hand we evaluated the scientific and technical devices feasibility and on the other hand we considered logistical and organisational aspects related to the project. For this reason we related to stakeholders and to local Authorities to better comprehend their issues, and find possible solutions and policies: in particular we were able to define quantities involved, collection, transport and storage strategies, operative problems related to different phases. This effort made possible the definition of a more effective solution: we were able to integrate ecological and technical issues with logistical and social aspects in order to define a holistic management strategy.