Eco-sustainable production of Poly-Hydroxy-Alkanoates (PHAs) and their use in composite materials for marine/coastal and agricultural/nursery applications
CNR, ISE – Leader of the Research Unit: Dr. Pietro Carlozzi
Project co-financed under Tuscany POR FESR 2014-2020
PHA PROJECT GOALS
The PHA Project aimed at developing a sustainable production process of polyhydroxyalkanoates (PHAs) using photosynthetic bacteria in new generation photobioreactors fed with agro-industrial wastewaters, and at producing thermoplastic biodegradable/compostable composites based on PHAs and low-cost natural fibres for applications in marine and terrestrial environments. Specifically new PHA composites are developed for the following applications:
- To produce articles for domestic uses (disposable cutlery, cups and plates);
- To produce jars and pots for terrestrial plant nursery:
- To produce jars and pots for marine plant nursery and tutors for coastal environmental engineering restoration interventions.
The partnership of PHA project is composed by the coordinator FETMO Engineering expert in mould making and processing of plastic by injection moulding, ZEFIRO masterbatch producer, Cooperativa Sociale Giovanile, service provider as, among many, beach cleaning and plant nursery, the Departments of Biology and of Civil and Industrial Engineering of University of Pisa, the Institute of Ecosystem Studies of National Research Council (CNR-ISE), supported by the subcontractor Laboratori ARCHA.
In terms of PHA production, during the project, a specific purple bacteria was selected and investigated as PHA producer, using two different low-cost agro-industrial wastewaters, coming from dairy and olive oil industry, as culture media. The process was scaled-up from indoor to outdoor pilot scale with a tubular photobioreactor, reaching a dry biomass productivity ranging from 86 to 149 mg/L day. The content of PHA reached a value >50% of dry biomass when growing indoors; the content reduced when the bacterium was grown outdoors.
Biodegradable composites based on PHA and natural fibres, such as fibres of Posidonia oceanica (PO), Wood Saw Dust (WSD) and bran were produced by extrusion in presence of appropriate amounts of plasticizer and filler. The composite granules were then processed by injection moulding to obtain different objects, from caps and plates for domestic uses (based on PHA/bran), to pots for terrestrial nursery (based on PHA/WSD), to pots and tutors for coastal/marine nursery (based on PHA/PO).
The biodegradability of the optimized composites was confirmed in different environments:
- under controlled composting conditions and in soil for the PHA/WSD composites, because their expected fate is to be treated in composting plants or used for applications in agriculture;
- in sea water on natural marine sediments in mesocosm and dune habitat for the PHA/PO composites, because their potential applications are in marine environment, such as natural engineering interventions (restoration of seagrass habitats).