**Acknowledgements**

This work was financed by "Klimahouse and energy production" in the framework of the programmatic-financial agreement with the Autonomous Province of Bozen-Bolzano of Research Capacity Building, which is gratefully acknowledged.

The authors want to thank Gianluca Turco (Department of Medicine, Surgery and Health Sciences, University of Trieste) for SEM pictures and Andrea Travan (Department of Life Science, University of Trieste) for help in foam production and characterization. Paolo Bonfiglio of Materiacustica srl is gratefully acknowledged for his precious advices.
