Chemical, physical and spectroscopic characterization of Posidonia oceanica (L.) Del. residues and their possible recycle

Posidonia is an endemic marine plant of the Mediterranean Basin forming wide grasslands involved in the oxygenation of seawaters, fauna protection and littoral erosion prevention. Starting from September–October, leaves and part of rhizomes detach off the marine plant and reach the beaches. Onshore residues represent a great environmental, economical, social and hygienic problem in all coastal zones of Mediterranean Basin because of the great disturb to the bathers and population, and the high costs for their removal and disposal to landfill.Authors characterized the onshore residues by means of physical, chemical and spectroscopic analyses in order to propose alternative solutions to the landfill and to reutilize them in agricultural applications as well as a source of energy.Physical, chemical and spectroscopic features of posidonia residues indicated a possible utilization in agriculture in their raw state. In facts, provided a reduction in the electrical conductivity and Na content, plant residual materials may be directly used as growing media or appropriately composted with raw materials of different provenance and basically opposite characteristics. In particular, the fibrous debris showed features similar to a bulking agent, while the leaves residues closely resembled a green waste. The fibrous portion of posidonia residues can be also utilized as biofuel according to their lower heating values (LHV) ranging between 13.6 and 15.7 MJ kg−1, whereas leaves debris are not so suitable for the energy recovery because their LHV were around 10 MJ kg−1.