Composting of Posidonia oceanica and Its Use in Agriculture
The extraordinary accumulation of deposits of the seaweed Posidonia oceanica on the beaches of Sardinia has given rise to a series of problems linked to its disposal. Leafy deposits of Posidonia oceanica are treated as refuse and disposed of in waste dump
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Introduction The disposal of the annual accumulation of Posidonia oceanica on the beaches of the Mediterranean causes a series of economic and environmental problems (Thelin and Giorgi. 1984). In this particular situation, the leafy deposits of Posidonia oceanica on the beach can be considered refuse, and at present they are transported to waste dumps, with the resulting loss of this enormous mass of organic material. It therefore seems of value to suggest an alternative system for recycling this waste in a way which satisfies the most recent U. E. directives. IDipartimento di Scienze Ambientali Agrarie Biotecnologie Agro - Alimentari, Sez. Chimica Agraria ed Ambientale,. Universita di Sassari, Viale Italia 39, 07100 Sassari, Italia 'Corresponding author. Tel: +39 - 079 - 229214, Fax: +39 - 079 - 229276 e-mail: [email protected] H. Insam, N. Riddech, S. Klammer (Eds.) Microbiology of Composting © Springer-Verlag Berlin Heidelberg 2002
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Refuse management places particular importance on the methods of recovery and recycling. Compo sting resolves this problem to a great extent and allows the part of the waste which is recyclable and useful for agriculture to be recovered (Melis et al. 1999 a). Posidonia oceanica is a material which in chemical terms, can be compared to other vegetal waste biomass (Baldissera Nordio et al. 1967; Melis et al. 1999 b). It is particularly rich in structural carbohydrates (CIN ratio> 65%) and thus suitable to combine in the right proportions with mainly nitric natural residues such as sludge, a potentially compostable waste material (Melis and Cattivello 1999).
Materials and Methods The matrices used for the preparation of the experimental trial, sludge from urban sewage, Posidonia oceanica from the beach and pruning wastes were analysed using the appropriate methods (Min. Agricoltura e Foreste 1989, 1991) to find the ideal mixture which would satisfy the physical and chemical parameters needed as a preliminary condition for correct composting (Szmidt 1997). The initial characteristics also took into consideration the quantity of heavy metals. Posidonia oceanica leaves have been collected from Alghero beach, Sassari (Sardinia), using a particular machine equipped with a rake. This has guaranteed a reduced removal of sand. Before of the preparation piles we provided for washing of the leaves with running water. This operation was done to prevent a possible negative influence of NaCl. After washing, the leaves were air dried and then ground in a crushing machine. The pruning wastes were treated in the same way. This allowed to be obtain ground material with dimensions between 5 to 10 cm. Because the leaves of Posidonia oceanica on the beach have a high structural carbohydrate content, and thus, as is well known, are not easily degraded, the mixtures were prepared with variable carbon residue content. One mixture (A) was prepared with a CIN ratio of 18, a second (B) with a CIN ratio of 22 and a third (C) with a CIN ratio of 36. One composting pile of each mixture w
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