The project has enabled to identify some methods of recovery of stranded posidonia residues and some methods of use of organic material to produce compost as soil amender for agricultural soils and/or as a cultivation substrate for the horticulture and the floriculture The project has carried out field surveys and analyzes on residues of stranded posidonia, in order to quantify the stranding of this biomass and identify their trend to re-use. It is possible to notice that there are permanent and wide deposits in stretches of coastline like inlet, rocky shore, especially with natural/artificial coastal protection structures such as cliffs and brushes. The problem arises when it is necessary to implement special measures of coastal cleaning. On the other hand, the “open” shore makes possible the natural phenomena of formation/demolition of banquettes, and it means that the removal operations are set from time to time even in tourist vocation resorts.
Scientific research has identified some methods of recovery of stranded posidonia residues and some methods of use of organic material to produce compost. Analysis have shown that the main limitations that composters set up against the use of this material are its high presence of salt and sand, in addition they have shown that the chemical composition of final compost does not contain heavy metals (an important aspect for the composters when choosing raw materials to produce compost), neither inside posidonia recovered along urbanized shoreline (like, in this case, the city of Bari). Since the Italian legislation requires separation of the sandy sediments from the organic residues before composting, the prototype “rotatory sieve” has been designed and developed, within the project P.R.I.M.E., which uses seawater (thus avoiding to waste fresh water) to separate the sand from the residues. The sieving operations must take place on the coast, and the sand recovered during this activity must be redistributed along the beach in order to preserve coasts as a whole and to give back seawater to its ecosystem.
The first example of temporary extended storage (about 140 m3) has been realized to reduce the initial salinity of stranded residues of posidonia, through the washing action of the rain. During the storage, the material has been turned over, so as to avoid the natural phenomena of putrefaction. At the end of the storage, the salinity of residues has proven to be good for the composting. Moreover, this method has allowed to obtain more information about time, rain quantity and method for preparing the storage area. Composting has been carried out in a composting establishment by testing different kinds of posidonia residues (stored or just collected), mixed with complementary organic materials usually used to produce compost amendment (sewage sludge, organic urban waste, agro-industrial residues, etc.)