Posidonia oceanica is important species of the marine ecosystems. However, large quantities of residues reaching the coastlines create pollution and high costs are required for their disposal. The objective was to investigate the bioconversion efficiency of P. oceanica residues as a source of feedstock in order to propose alternative solutions to the landfill. The residues were collected from the west coast of Turkey and hydrolyzed by both dilute sulfuric acid and cellulase. The maximum yield of reducing sugars was 21.6 g/L under the optimal conditions of enzyme pretreatment (7.5g substrate, 20 FPU, 90h), whereas 39.2 g/L was reached by consecutive enzymatic and acid hydrolysis. Bioethanol yield based on the sugar consumed was 62.3% corresponding to a productivity of 0.46 kg/m(3) h in flasks, whereas 0.76 kg/m(3) h was achieved in 2 L bioreactor. The results showed that P. oceanica residues can be utilized as a potential feedstock for the production of bioethanol. (C) 2013 Elsevier B.V. All rights reserved.